[E-Type] Which differential best?

E-Type
1

Miss Scarlet is a 70 FHC 4.2 with the standard 4-speed
tranny. When on the Interstate, she’s wound up tight as a
clock. I would like to change differential ratios, but
don’t know which one is best. I’m not even sure what ratio
I have now. Would a 2.88 too low? Will 3.07 make a
reasonable difference? Do I really need positraction? I
certainly don’t drive in the snow, or even in the rain, and
I don’t plan to do any sort of racing. As a fairly new
member to this forum, I would like to hear from anyone who
has had experience with differential ratio changes.–
Joe Parrott
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2

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Joe,
Odds are, your current diff is a 3.54, though some (like mine)
are 3.31. The difference between these is small, hardly noticeable
really. Dropping to a 3.07 will give you a noticeable lower RPM at
cruising speed, with a noticeable loss in acceleration. Going to a
2.88 will give a substantial loss in acceleration if you don’t do
anything to boost engine output. As an example, a friend of mine
has a S2 with a Terry’s CatClaw big-valve head. In theory, the
head adds about 50 hp. With his 2.88 diff, my stock 3.8 with 3.31
diff is considerably faster up to perhaps 80 mph or so. After that
the improved breathing of his head probably gives him a slight
edge, though we’ve never run them side-by-side. However, in normal
around-town driving, I’d much rather have my 3.31. His is nicer on
the highway though, with RPMs running 400-500 lower at speed.–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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3

You’ll find a lot of mixed and diverse opinions on this subject. I have a
'68 2+2 with the 4spd. It had a 3.54 fitted as std. Highway cruising was
a nightmare. I had it converted to the 3.07 and it made a LOT of
difference. Best $1.5k I spent on the car.

Some claim poorer acceleration and I guess the science prove that to be
correct. However, the car has so much torque anyway, that the “loss” in my
opinion is so small it’s of no consequence for my type of driving.

You might also hear some issues on having to slip the clutch too much. Not
true in my case. Seemes about the same as before. Actually I really do
feel that the car could easily take the 2.88 without too much worry re the
clutch.

Bottom line…depends on your driving style. If you’re an everyday
cruiser then these higher ratios are fine…if your a dash away from the
light type, then they will detract from that.

I feel the 3.07 has been an excellent compromise for me and my car.

Les.

From: “Joe Parrott” parrott@comcast.net
Reply-To: e-type@jag-lovers.org
To: e-type@jag-lovers.org
Subject: [E-Type] Which differential best?
Date: Fri, 4 Mar 2005 16:27:59 +0100

Miss Scarlet is a 70 FHC 4.2 with the standard 4-speed
tranny. When on the Interstate, she’s wound up tight as a
clock. I would like to change differential ratios, but
don’t know which one is best. I’m not even sure what ratio
I have now. Would a 2.88 too low? Will 3.07 make a
reasonable difference? Do I really need positraction? I
certainly don’t drive in the snow, or even in the rain, and
I don’t plan to do any sort of racing. As a fairly new
member to this forum, I would like to hear from anyone who
has had experience with differential ratio changes.

Joe Parrott
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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4

If you can afford it, leave the 3:54 and add a 5 speed.

[Original Message]
From: Ray Livingston rayl@atc.creative.com
To: e-type@jag-lovers.org
Date: 3/4/05 12:50:51 PM
Subject: Re: [E-Type] Which differential best?

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Joe,
Odds are, your current diff is a 3.54, though some (like mine)
are 3.31. The difference between these is small, hardly noticeable
really. Dropping to a 3.07 will give you a noticeable lower RPM at
cruising speed, with a noticeable loss in acceleration. Going to a
2.88 will give a substantial loss in acceleration if you don’t do
anything to boost engine output. As an example, a friend of mine
has a S2 with a Terry’s CatClaw big-valve head. In theory, the
head adds about 50 hp. With his 2.88 diff, my stock 3.8 with 3.31
diff is considerably faster up to perhaps 80 mph or so. After that
the improved breathing of his head probably gives him a slight
edge, though we’ve never run them side-by-side. However, in normal
around-town driving, I’d much rather have my 3.31. His is nicer on
the highway though, with RPMs running 400-500 lower at speed.

Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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5

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Joe,

You might find the car to be noisier with the 3.07.

My '64 has the 3.54:1 axle, and it was very unpleasant on the
highway when the 55 MPH speed limit was in effect. The car ran
about 2800 RPM at highway speeds then, and the car is at a
resonance peak there. I started thinking about getting a low
ratio, too.

Then the higher speed limits came in, and now I find that cruising
at 75-80, the car runs at 3500 RPM – where everything is a lot
quieter and smoother. Methinks that to go to a lower ratio would
only bring me back into the noisy region.

Gas mileage? I get well over 21 MPG at this 3500 RPM cruise, and I
have never got better at lower cruise speeds (I have measured MPG
at every single fillup, for over 30 years).

Extra wear? None of these cars are going to wear out given how we
drive them and how little we drive them. Engine problems are going
to come from elsewhere, if anywhere. I doubt that there would be
any extra wear at this RPM in any case, as the car is designed to
run near flat out all day long.

I’d suggest driving for a half hour at 2800-3000 RPM, which is
where you’d be cruising with a 3.07 axle, before you decide to make
the change.

Jerry–
Jerry Mouton
Palo Alto, California, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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6

In reply to a message from Les Halls sent Fri 4 Mar 2005:

Yeah…

I get this ‘‘my car has so much Torque’’ thing all the time
from the big block chevy guys insisting that they can run a
3.08 rear with a Muncie 4 speed and the car will pull no
matter what… HELLO WAKE UP! What everyone fails to
realize is WEAR AND TEAR on your clutch and transmission
will prevail faster than what it was normally designed for…

My M22 4 speeds can handle 700HP with proper rear end
gearing…I don’t sell them unless they are used with the
correct rear end gearing. Let me ask all of you… do you
think a transmission and clutch see more load or less load
with a 3.54 rear oppposed to a 3.07 rear using the same
engine pulling the same power figures???

Since very few of you don’t use the E-Type as a daily driver
maybe you’ll never see the clutch wear. Screw the theorical
bench racing stuff and look at it from a factual
perspective. A 2.88 or 3.07 will give you all the ecomony
you’ll need, providing you drive nice and normal. Few do
clutch dumps, holeshots with an E-type. If you did with the
3.07 you’d smoke the clutch FASTER than with a 3.54…–
The original message included these comments:

correct. However, the car has so much torque anyway, that the ‘‘loss’’ in my
opinion is so small it’s of no consequence for my type of driving.
You might also hear some issues on having to slip the clutch too much. Not

–
— Paul —
JT5 World Headquarters, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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7

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Shazam! Information overload. Thanks for the helpful
replies…I think I know what ratio I want now, based on
driving style, etc…But what about positraction–do I want
it? Do I need it?–
Joe Parrott
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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8

Let’s get real here…you’re right, not many of us use the car to it’s
max potential, therefore FOR ME and MY 2+2 the usefulness of the 3.07 far
outweighs the screaming 3.54…I really don’t care about max torque or
1,000,000 hp or whatever. This car is a GT, meant for high speed family
(very small family it’s true) cruising. It does it better with a 3.07 than
the 3.54. IMHO.

Les.

From: “5_Speeds” paul@punklegends.com
Reply-To: e-type@jag-lovers.org
To: e-type@jag-lovers.org
Subject: RE: [E-Type] Which differential best?
Date: Fri, 4 Mar 2005 18:56:55 +0100

In reply to a message from Les Halls sent Fri 4 Mar 2005:

Yeah…

I get this ‘‘my car has so much Torque’’ thing all the time
from the big block chevy guys insisting that they can run a
3.08 rear with a Muncie 4 speed and the car will pull no
matter what… HELLO WAKE UP! What everyone fails to
realize is WEAR AND TEAR on your clutch and transmission
will prevail faster than what it was normally designed for…

My M22 4 speeds can handle 700HP with proper rear end
gearing…I don’t sell them unless they are used with the
correct rear end gearing. Let me ask all of you… do you
think a transmission and clutch see more load or less load
with a 3.54 rear oppposed to a 3.07 rear using the same
engine pulling the same power figures???

Since very few of you don’t use the E-Type as a daily driver
maybe you’ll never see the clutch wear. Screw the theorical
bench racing stuff and look at it from a factual
perspective. A 2.88 or 3.07 will give you all the ecomony
you’ll need, providing you drive nice and normal. Few do
clutch dumps, holeshots with an E-type. If you did with the
3.07 you’d smoke the clutch FASTER than with a 3.54…

The original message included these comments:

correct. However, the car has so much torque anyway, that the ‘‘loss’’
in my
opinion is so small it’s of no consequence for my type of driving.
You might also hear some issues on having to slip the clutch too much.
Not

–
— Paul —
JT5 World Headquarters, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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9

In reply to a message from 5_Speeds sent Fri 4 Mar 2005:

I’m enjoying my swap to 2.88 from 3.54 on the V12 - but I’d rather
have a JT5 speed in there. Around town it’s not the greatest, but
it’s not a problem either. I just don’t need 4th very often.
The true value will be when driving long distance. I’m going to
Sebring tomorrow, and the JCNA meet in Georgia in September. We’ll
see how it does then. I’m thinking it will really pay off.–
Ginger, 1971 SIII FHC, 1966 SI OTS
Central Florida, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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10

how about Lime Rock?? what will it take to make you go ? :slight_smile: we’re going
to have to get the whole northeast gang to twist your arm…

pascal

Ginger writes:

In reply to a message from 5_Speeds sent Fri 4 Mar 2005:

I’m enjoying my swap to 2.88 from 3.54 on the V12 - but I’d rather
have a JT5 speed in there. Around town it’s not the greatest, but
it’s not a problem either. I just don’t need 4th very often.

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11

In reply to a message from Pascal sent Sat 5 Mar 2005:

Do your worst. I’m going to the mountains with my family in May.
Sorry.–
The original message included these comments:

how about Lime Rock?? what will it take to make you go ? :slight_smile: we’re going
to have to get the whole northeast gang to twist your arm…
pascal

–
Ginger, 1971 SIII FHC, 1966 SI OTS
Central Florida, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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12

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Joe
The e-types exported to Europe and Canada were equiped with a 3.07
ratio. The only reason I can see for equiping the US exports with a
3.54 was so it could go from 0 to 60 in less than 8 seconds. I
upgraded to the 3.07, and it was money well spent. The slight loss
in acceleration is more than made up for by the comfort gained at
highway speeds. The positraction is a nice feature, but probably
not as noticeable with the taller rear end. Whether or not you want
or need it depends on your driving style. If you already have it,
keep it. If you don’t have it, don’t bother adding it.
Joel–
The original message included these comments:

replies…I think I know what ratio I want now, based on
driving style, etc…But what about positraction–do I want
it? Do I need it?

–
ex jag
s.san francisco ca, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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13

In reply to a message from Joe Parrott sent Fri 4 Mar 2005:

Joe,

Well, how will you drive the car?

Without positraction, you will more likely get wheelspin in full
throttle launches.

Without positraction, you will get wheelspin of the inside wheel on
tight turns with throttle.

Without positraction, you’ll get stuck in snow, mud, or sand more
easily because when one wheel breaks traction, that’s it – no
traction at all.

Without positraction there will be some minor change in handling
because the rear wheels will not be (partially) locked together
with power out of turns. Not sure what the overall effect will be.

Overall, my guess is that the E Type will probably be pretty good
without it, except for the extremes. Not so likely to spin inside
rear wheels on turns, in any case.

Jaunts to the grocery store, you won’t notice any difference.

Light throttle cruising, no difference.

Warm, dry weather, no difference.

But it’s not really being used as a sports car, is it? For me,
that’s part of the whole deal. YMMV.

Jerry–
The original message included these comments:

driving style, etc…But what about positraction–do I want
it? Do I need it?

–
Jerry Mouton
Palo Alto, California, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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