[xj40] Re:diff whine

XJ40
1

Hi All,
Many of you may recall a situation I am in following a diff swap. I fitted
an LSD into my car from a donor vehicle. the diff was silent in the donor
car but whines once in my daily driver.
Due to heavy work duties of late it has been a few weeks since I have been
really able to investigate.
I have a theory which i would appreciate some feedback on.
If i jack up the car and ‘drive’ it up and down the range the diff appears
silent, once on the road however there is a specific whine at 40 and 70mph
which does appear to be getting worse.On the overun it almost sounds like a
groan at those speeds.
My thinking is like this.
If , when up on axle stands there is no noise at all at these speeds . or
any other,does this not pretty much discount the diff itself?
There is no load on the wheel/output bearings as the wheels are off the
ground and the load on the Diff itself will not vary very much whether the
wheels or in the air or on the ground.
Therefore, the whine MUST eminate from either wheel bearings or output
bearings, make sense?

Phil (UK)
'90 4.0 77K
'87 3.6 Sov, breaking for spares_________________________________________________________________
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2

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

From a pinnacle of ignorance of the subject, here’s my take on the
problem.

I don’t go along with your premise - ‘‘the load on the Diff itself
will not vary very much whether the wheels or in the air or on the
ground’’. Surely that can’t be true. The crown wheel and pinion are
under minimum load conditions with the wheels off the floor (just
the inertia of the rotating bits downstream of the diff.) but with
the wheels on the ground, the diff is trying to move nearly two
tons of motor car - or slow it down somewhat on the overun.

It’s my experience that if the diff itself is ‘noisy’, that noise
will be there all the time - it just varies in frequency and
amplitude depending on speed and whether its under power, on the
dwell or on the overun. It may be that you only hear it at certain
times but that is usually because it is amplified by something
picking up it’s natural frequency and transmitting it in to the
cabin. (Remember Brett’s ‘A’ frame bushes?)

Similarly with a bearing - wheel, output or pinion shaft. If it’s
knackered it will make noise all the time but that noise may not
become apparent to you until it is amplified by being put under
load. In the case of the wheel bearings and output bearings for
example, I would expect the noise they make to become more
noticeable with speed and perhaps with cornering forces (the XJ40
drive shafts also acting as the upper control arm of the suspension
of course).

Since your problem is only apparent at specific road speeds, it
sounds to me that it is only at those speeds that noise from a
bearing under load (power or overun) is hitting the natural
frequency of something else on the car. Could it be that the centre
bearing is transmitting diff. pinion or output bearing noise at
those speeds? You could mark it’s current position and then try it
at slightly different angles.

My twopenny worth!–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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3

Bearing noises from Jaguar diffs can be very frustrating. At our old shop, I
can recall a fair number of cars that clearly had diff bearing noises but on
the lift with a good mechanic’s stethoscope, we could not locate the noisy
bearings. They don’t all do this, but we’ve seen it happen a bunch.

The other one that amazed me was a car that had almost a full inch of axial
play at the diff output bearings and yet was as quiet as a mouse!

Best regards,

Gregory Wells 800-331-2193 x103
Coventry West, Inc. - Atlanta, GA www.coventrywest.com
New, Rebuilt, and Used Jaguar & Land-Rover Parts

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4

Bryan,
I certainly do not disagree with you at all, my thoughts however are based
on the assumption that the drive shafts would absorb much of the torque
allowing the load on the diff to be relatively unchanged.
The really annoying aspect of this is that the car was silent with the
original diff in. The LSD was equally quiet in the donor.
I swapped the lot over whilst keeping the original hubs.
The whine was immediatley evident once fitted.
I swapped the A frame back over to the original thinking that the bushes
would have ‘set’ in the frame and perhaps that was the problem. No
different, I changed the oil for semi synthetic and the whine certainly was
a little quieter.However , in the last 1K when i have had no time to do
anything but drive, the noise has definately increased and indeed has now
introduced a vibration!
The whine is MOST prominent at 40/70 and 90 but exists all the time and
becomes almost a groan on the overun.
I fully understand and agree that it is likely to be something allowing the
noise to intrude into the cabin , but can I find it?
I am reluctant to just renew the A frame bushes and output bearings as there
is good evidance that suggests they are fine!

Phil (UK)
'90 4.0 77K
'87 Sov 3.6 breaking for spares>From: Bryan N sophistic@btopenworld.com

To: xj40@jag-lovers.org
Subject: [xj40] Re:diff whine
Date: Fri, 7 Feb 2003 15:01:37 +0100

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

From a pinnacle of ignorance of the subject, here’s my take on the
problem.

I don’t go along with your premise - ‘‘the load on the Diff itself
will not vary very much whether the wheels or in the air or on the
ground’’. Surely that can’t be true. The crown wheel and pinion are
under minimum load conditions with the wheels off the floor (just
the inertia of the rotating bits downstream of the diff.) but with
the wheels on the ground, the diff is trying to move nearly two
tons of motor car - or slow it down somewhat on the overun.

It’s my experience that if the diff itself is ‘noisy’, that noise
will be there all the time - it just varies in frequency and
amplitude depending on speed and whether its under power, on the
dwell or on the overun. It may be that you only hear it at certain
times but that is usually because it is amplified by something
picking up it’s natural frequency and transmitting it in to the
cabin. (Remember Brett’s ‘A’ frame bushes?)

Similarly with a bearing - wheel, output or pinion shaft. If it’s
knackered it will make noise all the time but that noise may not
become apparent to you until it is amplified by being put under
load. In the case of the wheel bearings and output bearings for
example, I would expect the noise they make to become more
noticeable with speed and perhaps with cornering forces (the XJ40
drive shafts also acting as the upper control arm of the suspension
of course).

Since your problem is only apparent at specific road speeds, it
sounds to me that it is only at those speeds that noise from a
bearing under load (power or overun) is hitting the natural
frequency of something else on the car. Could it be that the centre
bearing is transmitting diff. pinion or output bearing noise at
those speeds? You could mark it’s current position and then try it
at slightly different angles.

My twopenny worth!

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
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5

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

I have been trying to imagine what you actually did or did not do
in executing the change from the donor car. If you took the entire
diff / ‘A’ frame assembly off the quiet donor car and attached the
original hubs on the output side, you presumably connected it up to
the original prop-shaft on the input side.

Did you have to loosen the prop-shaft centre bearing mount to
displace the shaft for removal from the pinion flange? If so, I
wonder if you put it back in the correct alignment with the
exchanged diff. I believe Brett could see the prop shafts
oscillating when his centre bearing was out of alignment as he ran
it in ‘drive’ up on jack stands. Did you notice anything like that?

Would it be possible to put a little load on the drive train by
running it up to an indicated 40 mph (the speed where you normally
get the noise) and keeping it there for a very short period whilst
someone gently applied the brakes to see if you can produce the
noise under load? Brakes may get a little hot though!

Now that you feel vibration as well as noise, I reckon you should
concentrate on that centre bearing alignment.

Just another tuppence worth!–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
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6

Phil,
Following this thread and knowing little about to which you and Bryan are
speaking (never stopped me before!), I figured I would just make the remark
that after listening to the conversation, the logical point I keep hearing
is that you were able to affect the tone and tenor of the noise by adding a
thicker lube to the differential. This would lead me to think, dispite all
the contrary, that the problem lies within the difeerential.
With all I have read in the past about balanced propshafts and pinions,
could it not be that the new differential just does not match the old system
in terms of balance and that the noise is coming from the fact that the
components are EVER so slightly off skew and resonating into the
differential thus affected by thicker dampening (the lube)?

Just a thought.

Clark
'88 XJ40
'67 S-Type
'67 420----- Original Message -----
From: “Phil Parrington” pp221158@hotmail.com
To: sophistic@btopenworld.com; xj40@jag-lovers.org
Sent: Friday, February 07, 2003 11:34 AM
Subject: Re: [xj40] Re:diff whine

Bryan,
I certainly do not disagree with you at all, my thoughts however are
based
on the assumption that the drive shafts would absorb much of the torque
allowing the load on the diff to be relatively unchanged.
The really annoying aspect of this is that the car was silent with the
original diff in. The LSD was equally quiet in the donor.
I swapped the lot over whilst keeping the original hubs.
The whine was immediatley evident once fitted.
I swapped the A frame back over to the original thinking that the bushes
would have ‘set’ in the frame and perhaps that was the problem. No
different, I changed the oil for semi synthetic and the whine certainly
was
a little quieter.However , in the last 1K when i have had no time to do
anything but drive, the noise has definately increased and indeed has now
introduced a vibration!
The whine is MOST prominent at 40/70 and 90 but exists all the time and
becomes almost a groan on the overun.
I fully understand and agree that it is likely to be something allowing
the
noise to intrude into the cabin , but can I find it?
I am reluctant to just renew the A frame bushes and output bearings as
there
is good evidance that suggests they are fine!

Phil (UK)
'90 4.0 77K
'87 Sov 3.6 breaking for spares

From: Bryan N sophistic@btopenworld.com
To: xj40@jag-lovers.org
Subject: [xj40] Re:diff whine
Date: Fri, 7 Feb 2003 15:01:37 +0100

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

From a pinnacle of ignorance of the subject, here’s my take on the
problem.

I don’t go along with your premise - ‘‘the load on the Diff itself
will not vary very much whether the wheels or in the air or on the
ground’’. Surely that can’t be true. The crown wheel and pinion are
under minimum load conditions with the wheels off the floor (just
the inertia of the rotating bits downstream of the diff.) but with
the wheels on the ground, the diff is trying to move nearly two
tons of motor car - or slow it down somewhat on the overun.

It’s my experience that if the diff itself is ‘noisy’, that noise
will be there all the time - it just varies in frequency and
amplitude depending on speed and whether its under power, on the
dwell or on the overun. It may be that you only hear it at certain
times but that is usually because it is amplified by something
picking up it’s natural frequency and transmitting it in to the
cabin. (Remember Brett’s ‘A’ frame bushes?)

Similarly with a bearing - wheel, output or pinion shaft. If it’s
knackered it will make noise all the time but that noise may not
become apparent to you until it is amplified by being put under
load. In the case of the wheel bearings and output bearings for
example, I would expect the noise they make to become more
noticeable with speed and perhaps with cornering forces (the XJ40
drive shafts also acting as the upper control arm of the suspension
of course).

Since your problem is only apparent at specific road speeds, it
sounds to me that it is only at those speeds that noise from a
bearing under load (power or overun) is hitting the natural
frequency of something else on the car. Could it be that the centre
bearing is transmitting diff. pinion or output bearing noise at
those speeds? You could mark it’s current position and then try it
at slightly different angles.

My twopenny worth!

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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7

Phil,

The load experienced by the components within the differential most
definitely will vary in regards to whether the “wheels” are on a hard
surface or elevated via jack stands. When driving, the differential is
transmitting engine output to the driven wheels … possibly hundreds of
horsepower. On the stand, the wheels are only seeing the minimal load
necessary to spin them. Gear and anti-friction bearing noises will vary in
accordance with load. Bryan is correct in informing you that all gear
trains and anti-friction bearings make noise to some extent … they are
certainly not quiet when in operation.

From your posted information, I would suggest the following reasonable
conclusions:

  1. If your car was quiet before the differential change, then its NOT the
    wheel bearings. I believe you previously mentioned that you changed just to
    get the “limited slip differential”. Not a bad thing, I like limited slip
    diffs too.

  2. If the donor limited slip differential was quiet in the donor car (as
    you mentioned) then the problem is NOT the differential gears or any of the
    anti-friction bearings.

Part of my “day job” is to figure out why some “component” is not
functioning correctly. Many times, its specifically the case that its not
functioning after some type of repair or maintenance. I always ask myself
the basic question of “What’s changed since it last ran correctly?”

In your case, I would ask … “Are all the fasteners correctly secured?” or
better still, “What about the sub-frame bushings in the rear?” Your removal
/ replacement of these components may have changed or disturbed their
functionality. Brett fought the battle of ghostly differential whine and
lost numerous times until he changed the sub-frame bushings. Thorough
inspection and/or replacement of these bushings would be a great starting
point … and not really expensive either.

Good Luck,
John P.

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8

Clark,Bryan
I am convinced that the Diff itself is basically sound. You have both
mentioned the centre bearing. Certainly when the rear frame was removed I
had no need to unbolt the centre bearing at all. It was literally a straight
swap. The input end was unbolted at the jurid and dropped out!I shall look
very closely over the next few days as I have some time off, it is driving
me nuts.

Phil>From: “Clark Westneat” cwestneat@alltel.net

To: “Phil Parrington” <@Phil-P>, sophistic@btopenworld.com,
xj40@jag-lovers.org
Subject: Re: [xj40] Re:diff whine
Date: Fri, 7 Feb 2003 12:06:23 -0500

Phil,
Following this thread and knowing little about to which you and Bryan
are
speaking (never stopped me before!), I figured I would just make the remark
that after listening to the conversation, the logical point I keep hearing
is that you were able to affect the tone and tenor of the noise by adding a
thicker lube to the differential. This would lead me to think, dispite all
the contrary, that the problem lies within the difeerential.
With all I have read in the past about balanced propshafts and
pinions,
could it not be that the new differential just does not match the old
system
in terms of balance and that the noise is coming from the fact that the
components are EVER so slightly off skew and resonating into the
differential thus affected by thicker dampening (the lube)?

Just a thought.

Clark
'88 XJ40
'67 S-Type
'67 420

----- Original Message -----
From: “Phil Parrington” <@Phil-P>
To: sophistic@btopenworld.com; xj40@jag-lovers.org
Sent: Friday, February 07, 2003 11:34 AM
Subject: Re: [xj40] Re:diff whine

Bryan,
I certainly do not disagree with you at all, my thoughts however are
based
on the assumption that the drive shafts would absorb much of the torque
allowing the load on the diff to be relatively unchanged.
The really annoying aspect of this is that the car was silent with the
original diff in. The LSD was equally quiet in the donor.
I swapped the lot over whilst keeping the original hubs.
The whine was immediatley evident once fitted.
I swapped the A frame back over to the original thinking that the
bushes
would have ‘set’ in the frame and perhaps that was the problem. No
different, I changed the oil for semi synthetic and the whine certainly
was
a little quieter.However , in the last 1K when i have had no time to do
anything but drive, the noise has definately increased and indeed has
now
introduced a vibration!
The whine is MOST prominent at 40/70 and 90 but exists all the time and
becomes almost a groan on the overun.
I fully understand and agree that it is likely to be something allowing
the
noise to intrude into the cabin , but can I find it?
I am reluctant to just renew the A frame bushes and output bearings as
there
is good evidance that suggests they are fine!

Phil (UK)
'90 4.0 77K
'87 Sov 3.6 breaking for spares

From: Bryan N sophistic@btopenworld.com
To: xj40@jag-lovers.org
Subject: [xj40] Re:diff whine
Date: Fri, 7 Feb 2003 15:01:37 +0100

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

From a pinnacle of ignorance of the subject, here’s my take on the
problem.

I don’t go along with your premise - ‘‘the load on the Diff itself
will not vary very much whether the wheels or in the air or on the
ground’’. Surely that can’t be true. The crown wheel and pinion are
under minimum load conditions with the wheels off the floor (just
the inertia of the rotating bits downstream of the diff.) but with
the wheels on the ground, the diff is trying to move nearly two
tons of motor car - or slow it down somewhat on the overun.

It’s my experience that if the diff itself is ‘noisy’, that noise
will be there all the time - it just varies in frequency and
amplitude depending on speed and whether its under power, on the
dwell or on the overun. It may be that you only hear it at certain
times but that is usually because it is amplified by something
picking up it’s natural frequency and transmitting it in to the
cabin. (Remember Brett’s ‘A’ frame bushes?)

Similarly with a bearing - wheel, output or pinion shaft. If it’s
knackered it will make noise all the time but that noise may not
become apparent to you until it is amplified by being put under
load. In the case of the wheel bearings and output bearings for
example, I would expect the noise they make to become more
noticeable with speed and perhaps with cornering forces (the XJ40
drive shafts also acting as the upper control arm of the suspension
of course).

Since your problem is only apparent at specific road speeds, it
sounds to me that it is only at those speeds that noise from a
bearing under load (power or overun) is hitting the natural
frequency of something else on the car. Could it be that the centre
bearing is transmitting diff. pinion or output bearing noise at
those speeds? You could mark it’s current position and then try it
at slightly different angles.

My twopenny worth!

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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On
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9

Phil,
Al things being equal, there must be some sort of mis-match between the
new differential and the old propshaft. I just remember Brett having a
nightmare with this exact sort of thing about 18 months ago.
I am just glad my '88 doesn’t have the new improved jurid system. Maybe
that is part of the problem. Aren’t the '87 and the '90 two different
systems on connection??

Clark
'88 XJ40
'67 S-Type
''67 420

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10

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Phil,

There may be a clue here! You say :-

‘‘The input end was unbolted at the jurid and dropped out!’’

On my car, it is not possible to remove the prop shaft from the
jurid / pinion flange without first undoing the centre bearing
mount because the prop shaft has to be slid further forward on the
splined section than the flexible mounting of the centre bearing
allowed to clear the long spigot on the pinion shaft. That spigot
firmly locates the jurid central to the propshaft and pinion shaft
flanges to ensure they are concentric. I think Brett found that on
a jurid with a badly worn central hole, (and hence an ill-fitting
spigot) it was possible to get the two shafts slightly out of
alignment and introduce noise and/or vibration.

I note in a couple of sectioned drawings I’ve seen of the diff.,
the spigot on the pinion shaft is not shown. I wonder if they
originally produced them that way and the one you fitted does not
have the spigot, hence your problem?

That’s sixpence worth so far! :-)–
The original message included these comments:

mentioned the centre bearing. Certainly when the rear frame was removed I
had no need to unbolt the centre bearing at all. It was literally a straight
swap. The input end was unbolted at the jurid and dropped out!I shall look

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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11

I certainly have no clue.

My car was totally quiet, then I changed the lube to synthetic
75w90 lube, and after a short time and a long trip, the
diff whined like mad.

A rebuilt one lasted about 10 months and started making noise, and was
replaced with another rebuilt (free from Hal Rogers), but that one
started making noise shortly after.
Tried thicker lube, 85w140, no change.
Ordered a rebuilt from Coventry west, went with the power loc
and it was noisy in a week, as were the next two replacements.
(Coventry West stands behind their products)

Put new sub frame bushings in and the noise was reduced 90%, to just
audible if listened for.
The addition of Lucas lube oil stabilizer (honey like product) eliminated
the whine totally, eliminated driveline clunks, and eliminated
the power loc function!

I know the source of the noise is the pinion bearing/gear setup,
a slight excess of play in the bearings and gears causes noise.
Under normal conditions, I don’t think you would hear the noise,
but under some conditions, the noise is transmitted into the car
with extreme efficiency.
I added sound proofing, and undercoating without much improvement.

My problem started after changing the lube, so I don’t recommend changing
it.
It might just have been time for the diff to wear out, who knows…

I know, if my diff was noisy, I would try the Lucas lube and sub frame
bushings first.

Inspection of my original diff showed all the parts inside in good shape,
no serious wear, bearings slightly worn but ok, as was the pinion gear.

The entire XJ40 driveline setup is a mess, center bearing is no good,
jurid is a bad design, diff is a mess…

I fixed all the problems on my car, after a LOT of work, so
now its for sale…???

Brett
1990 XJ6

Phil,
Al things being equal, there must be some sort of mis-match
between the
new differential and the old propshaft. I just remember Brett having a
nightmare with this exact sort of thing about 18 months ago.
I am just glad my '88 doesn’t have the new improved jurid
system. Maybe
that is part of the problem. Aren’t the '87 and the '90 two different
systems on connection??

Clark
'88 XJ40
'67 S-Type
''67 420

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12

When everything was tightened, was every thing in the
proper alignment?
I have worked on some cars and had to load a-frames
and such before snugging things down.

Just a thought

Dave

91 xj6 sov dallas__________________________________________________
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13

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Hi, I would like to put some thing straight here regards the ‘diff’
noise problem(s)
The on the lift/jack, with wheels free, the diff’ output bearings
are loaded outward from the diff’(The axle shafts are trying to
pull the diff’ apart.) by the leverage of the road wheel assembley
on the drive axle. IE: The drive axle shaft is in tension…
With the car on the ground the drive axle shaft is now under
compression pushing into the diff bearins ( diff’ is now being
compressed or squashed.) and so changing the loading on all
the ‘across car bearings’… Jaguar rear axle design is unlike
other makes in that the rotating axle shaft is acting as a
structural member, taking the place of an upper ‘A’ arm and it’s
joint. therefore the diff’ side cover brearings are not just taking
turning torque load but side loading too. This means if you lift
the car to listen for wheel bearing noise the loading will change
the bearing running load and reduce or eliminate the ‘on road’ load
noise…, the only way to duplicate a diff’ bearing or road wheel
noise in the shop is to duplicate the ‘on the road’ loading by
running on a chassis dynomometer or wheel rollers with the load of
the vehicle on the wheels…
Hope this clarifies some issues folk have, diagnosing wheel/diff’
bearing noises…–
The original message included these comments:

Many of you may recall a situation I am in following a diff swap. I fitted
If I jack up the car and ‘drive’ it up and down the range the diff appears
If , when up on axle stands there is no noise at all at these speeds . or
There is no load on the wheel/output bearings as the wheels are off the

–
Noddy
Purcell/Oklahoma, United States
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14

The driveshaft part that plugs onto the diff spigot (inside the jurid)
has a bushing and seal, that holds the driveshaft centered on the spigot.
The actual bushing wears, and the seal cracks.
This allows the driveshaft to get off center, and its not going
to be held by the jurid, because its flexible.
Removing these bits can allow even more offset, as the jurid has
a lot of slop in its mounting bolts.
The jurid is fit, and balanced at the factory, as an assembly,
including the entire driveshaft.
I suppose the jurid is fit in some sort of jig to hold it centered,
then balanced.
You can remove the jurid from the diff IF the bushing is good,
if its got play, things will go together offset under the weight/stress
of the mis alignment.

I have also seen two types of jurid, one is thicker than the other
by a slight amount…

Its not possible to remove the jurid without tearing the center bearing
rubber,
as the shaft must move forward about 4 inches to get it off the spigot.
Only if you moved the diff back before, or move the center bearing would
you be able to get the jurid out.
(on my car)

Brett
1990 XJ6

Phil,

There may be a clue here! You say :-

‘‘The input end was unbolted at the jurid and dropped out!’’

On my car, it is not possible to remove the prop shaft from the
jurid / pinion flange without first undoing the centre bearing
mount because the prop shaft has to be slid further forward on the
splined section than the flexible mounting of the centre bearing
allowed to clear the long spigot on the pinion shaft. That spigot
firmly locates the jurid central to the propshaft and pinion shaft
flanges to ensure they are concentric. I think Brett found that on
a jurid with a badly worn central hole, (and hence an ill-fitting
spigot) it was possible to get the two shafts slightly out of
alignment and introduce noise and/or vibration.

I note in a couple of sectioned drawings I’ve seen of the diff.,
the spigot on the pinion shaft is not shown. I wonder if they
originally produced them that way and the one you fitted does not
have the spigot, hence your problem?

That’s sixpence worth so far! :slight_smile:

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
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15

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Read the bit you said about whine on overrun- check the pinion
nut torque, and find the spec for what pinion bearing preload is
supposed to be-if it has loosened up even slightly, maybe you can
get some silence by tightening the nut up a bit more, not to exceed
spec from Tech Data.–
Jerry Goldman
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16

Jerry
Yes,
The problem is, the more you fool with it, the less the nut locks,
as the locktite type stuff does not work well once
its broken.(the blue stuff on the threads)

I had luck tightening my nut up just a slight amount, then went one step
more,
and it loosened up over time, making a horrible noise.
I replaced the differential, and found no problem with the old one
except the nut was loose…

Brett
1990 XJ6

In reply to a message from Phil Parrington sent Fri 7 Feb 2003:

Read the bit you said about whine on overrun- check the pinion
nut torque, and find the spec for what pinion bearing preload is
supposed to be-if it has loosened up even slightly, maybe you can
get some silence by tightening the nut up a bit more, not to exceed
spec from Tech Data.

Jerry Goldman
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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for exciting services and resources including Photo Albums,
Event Diary / Calendar, On Line Books and more !

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17

In reply to a message from tomsprechs@yahoo.com sent Tue 11 Feb 2003:

Jerry,

On an XJ40, there is not a torque figure specified for the pinion
nut itself in the Tech Specs. The pinion bearing pre-load is set
using the crush tube method by measuring the BACKLASH torque ( i.e.
the torque required to take up the play between the crown wheel and
pinion) and that is measured only in lb/INCHES (Spec = 35 - 55
lb/inch).

It’s a ‘one-shot’ type excercise because if you tighten the pinion
nut a fraction too far and exceed the backlash torque specification
the crush tube is knackered and you have to start all over with a
new crush tube.

On my car, the pinion nut itself was so tight, I could not undo
it with a long breaker-bar when I tried to replace the pinion shaft
seal. I had to take the car to a shop and have them remove it with
an air impact wrench. No doubt that was due in some part to the
application of ‘thread lock’ during initial build, but if that is
the case with other XJ40 pinion nuts, you really have no chance
of ‘tightening it up a bit more’ as you suggest without a serious
risk of overdoing it, exceeding the backlash torque, ruining the
crush tube and if left in that state, the pinion bearing itself.

As Brett has mentioned, he found out that messing with the pinion
nut is at best a temporary relief and IMHO it potentially will do
more harm than good.–
The original message included these comments:

Read the bit you said about whine on overrun- check the pinion
nut torque, and find the spec for what pinion bearing preload is
supposed to be-if it has loosened up even slightly, maybe you can
get some silence by tightening the nut up a bit more, not to exceed
spec from Tech Data.

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
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18

I have tried tightening the pinion nut on a few differentials,
some I could move it, on others, I could put a 5 foot pipe on the end
of a ratchet, stand on it, jump on it, and not budge the nut.

I did get good results if I could just turn the nut slightly, I
marked the nut, then moved it one degree? and reduced the noise
quite a bit.
I did not notice any more force needed to turn the diff in the backlash
mode.

I thought, a little is good, so more is better, and went another degree,
and things were very quiet for a while, then a very nasty grinding noises
stared coming from the differential.
I thought, ok, I trashed the bearings.
I bought a rebuilt diff and fit it, took the original diff apart and found
the bearings looked like they had 80,000 miles on them (they did),
but nothing really wrong. The races looked like the typical wheel bearing
with mileage on them, not bad, just some signs of wear.

Before taking the diff apart, I found the pinion flange easy to turn,
with grinding noises, and on taking the nut off, found it somewhat loose,
and after inspecting things and tightening up the nut, found the diff
smooth and quiet.

When the rebuilt diff got noisy (10 months later), I tried to go one
degree on the nut, but could not budge it.

I think its a valid method to get rid of the noise by tweaking
the pinion nut, to remove the play from bearing and gear wear
(slight but noisy), as long as you don’t go too far, and the nut
stays tight.
I never tried removing the nut, adding fresh locktite, and re doing it, as
the marks might be lost, and you would need to really play with it in order
to get the preload correct, and I don’t know if you could with the diff
in the car.
Dealers do it with seal replacement, and maybe you could just
get them to go a bit more tight on the nut than it was, say 1 degree…

New sub frame bushings and thicker lube might be a better idea though.

Keep in mind, I made lots of experiments out of curiosity,
both with differentials and drive shafts, looking for a really quiet
and smooth car.

Brett
1990 XJ6 (quiet differential)

Jerry,

On an XJ40, there is not a torque figure specified for the pinion
nut itself in the Tech Specs. The pinion bearing pre-load is set
using the crush tube method by measuring the BACKLASH torque ( i.e.
the torque required to take up the play between the crown wheel and
pinion) and that is measured only in lb/INCHES (Spec = 35 - 55
lb/inch).

It’s a ‘one-shot’ type excercise because if you tighten the pinion
nut a fraction too far and exceed the backlash torque specification
the crush tube is knackered and you have to start all over with a
new crush tube.

On my car, the pinion nut itself was so tight, I could not undo
it with a long breaker-bar when I tried to replace the pinion shaft
seal. I had to take the car to a shop and have them remove it with
an air impact wrench. No doubt that was due in some part to the
application of ‘thread lock’ during initial build, but if that is
the case with other XJ40 pinion nuts, you really have no chance
of ‘tightening it up a bit more’ as you suggest without a serious
risk of overdoing it, exceeding the backlash torque, ruining the
crush tube and if left in that state, the pinion bearing itself.

As Brett has mentioned, he found out that messing with the pinion
nut is at best a temporary relief and IMHO it potentially will do
more harm than good.

The original message included these comments:

Read the bit you said about whine on overrun- check the pinion
nut torque, and find the spec for what pinion bearing preload is
supposed to be-if it has loosened up even slightly, maybe you can
get some silence by tightening the nut up a bit more, not to exceed
spec from Tech Data.

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org
for exciting services and resources including Photo Albums,
Event Diary / Calendar, On Line Books and more !

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19

Brett,
When the diff was removed ,it was all unbolted and drawn BACK off the prop,
leaving the jurid attached to the propshaft. The jurid, centre bearing etc
were all untouched.

Phil>From: Brett Gazdzinski brett.gazdzinski@wcom.com

To: xj40@jag-lovers.org
Subject: RE: [xj40] Re:diff whine
Date: Mon, 10 Feb 2003 14:19:31 -0500

The driveshaft part that plugs onto the diff spigot (inside the jurid)
has a bushing and seal, that holds the driveshaft centered on the spigot.
The actual bushing wears, and the seal cracks.
This allows the driveshaft to get off center, and its not going
to be held by the jurid, because its flexible.
Removing these bits can allow even more offset, as the jurid has
a lot of slop in its mounting bolts.
The jurid is fit, and balanced at the factory, as an assembly,
including the entire driveshaft.
I suppose the jurid is fit in some sort of jig to hold it centered,
then balanced.
You can remove the jurid from the diff IF the bushing is good,
if its got play, things will go together offset under the weight/stress
of the mis alignment.

I have also seen two types of jurid, one is thicker than the other
by a slight amount…

Its not possible to remove the jurid without tearing the center bearing
rubber,
as the shaft must move forward about 4 inches to get it off the spigot.
Only if you moved the diff back before, or move the center bearing would
you be able to get the jurid out.
(on my car)

Brett
1990 XJ6

Phil,

There may be a clue here! You say :-

‘‘The input end was unbolted at the jurid and dropped out!’’

On my car, it is not possible to remove the prop shaft from the
jurid / pinion flange without first undoing the centre bearing
mount because the prop shaft has to be slid further forward on the
splined section than the flexible mounting of the centre bearing
allowed to clear the long spigot on the pinion shaft. That spigot
firmly locates the jurid central to the propshaft and pinion shaft
flanges to ensure they are concentric. I think Brett found that on
a jurid with a badly worn central hole, (and hence an ill-fitting
spigot) it was possible to get the two shafts slightly out of
alignment and introduce noise and/or vibration.

I note in a couple of sectioned drawings I’ve seen of the diff.,
the spigot on the pinion shaft is not shown. I wonder if they
originally produced them that way and the one you fitted does not
have the spigot, hence your problem?

That’s sixpence worth so far! :slight_smile:

–
Bryan N ('91 Sovereign)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !

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