[xk] Gearbox Ratios

dear all,

the ratios in gearbox is an interesting subject and I put together the list
of ratios below for our local jaguar club magazine the only missing ratios
is for 3.8 litre E type. which I now have.

First gear is way to low for an XK ie 3.375 the CR ratio is much nicer at
2.98 but if you drop a set of 2.4 MK1 / MK11 non synchro gears hey presto
you have a very usuable first gear at a price a lot less than finding an XK
CR gearbox. Even MK2 3.4 etc is an improvement and is very close to CR ratio

Gearbox Ratios

Several people have asked me what the gear ratios are in Jaguar gearboxes.
This of course affects the driveability of a car. This information is of
course important when different gearboxes are being fitted and differential
ratios changed. Someone else can interpret how the change in these ratios
will change the way your jag drives and accelerates.

Gearbox Ratios

MKV, MKVII, XK120, XK140, XK150

1st 3.375.1

2nd 1.982.1

3rd 1.367.1

4th 1.1

XK120, XK140, XK150 close ratio when fitted

1st 2.98.1

2nd 1.74.1

3rd 1.21.1

4th 1.1

MK2 2.4 litre

1st 2.67

2nd 1.74

3rd 1.25

4th 1.1

3.4 / 3.8 MK2 / S Type, 4.2 MKX, 420, E Type 4.2 2+2

1st 3.04

2nd 1.97

3rd 1.32

4th 1.1

E Type Series 1 3.8 Coupe /Roadster

1st 3.377

2nd 1.86

3rd 1.283

1st 1.1

close ratios

1st

E Type Series I 4.2 Coupe / Roadster

1st 2.68-1

2nd 1.74-1

3rd 1.27-1

4th 1-1

XJ 2.8 / 4.2, E Type Series II and V12 E Types

1st 2.933.1

2nd 1.905-1

3rd 1.389-1

4th 1-1

Overdrive on XK140 / XK150, MK1, MK2

Overdrive .779

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

1 Jul 2007 10:53:33 +0200

The gearbox ratios for the overdrive boxes were the same
(there was also a close ratio version but that’s not
dependant on having an overdrive). With the overdrive fitted
Jaguar changed the default rear axle ratio.

For the XK150 without overdrive the normal axle ratio was 3.54:1

With the overdrive the ratio was 4.09:1 giving an effective
3.19:1 ratio with the overdrive engaged.From: “Ken Green” ken.green@kgcc.co.uk
Subject: Re: [xk] Gearbox options

I found the gearbox ratios for 120 moss box as:
first 3.375
second 1.982
third 1.367
top 1
does anyone know if the moss box with overdrive is the
same?

Terry,

This would be a lot more useful if you identified Gearbox Model by
Serial Number with Jaguar Model, rather than just Jaguar Model which can
be ambiguous where a particular model can have a number of gearbox
choices.

For example:-

1964 to 1968 (Series 1) 4.2 Litre E-Type (roadster and fhc) can have
usual all-syncro EJxxxx gearbox, which is “close-ratio”, or fairly rare
EExxxx gearbox with “wide-ratio”.

Roger Payne
PO Box 32
ERINDALE CENTRE
A.C.T. 2903
Australia-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf
Of Terry McGrath
Sent: Monday, 2 July 2007 9:47 AM
To: xk@jag-lovers.org
Subject: [xk] Gearbox Ratios

dear all,

the ratios in gearbox is an interesting subject and I put together the
list
of ratios below for our local jaguar club magazine the only missing
ratios
is for 3.8 litre E type. which I now have.

First gear is way to low for an XK ie 3.375 the CR ratio is much nicer
at
2.98 but if you drop a set of 2.4 MK1 / MK11 non synchro gears hey
presto
you have a very usuable first gear at a price a lot less than finding an
XK
CR gearbox. Even MK2 3.4 etc is an improvement and is very close to CR
ratio

Gearbox Ratios

Several people have asked me what the gear ratios are in Jaguar
gearboxes.
This of course affects the driveability of a car. This information is
of
course important when different gearboxes are being fitted and
differential
ratios changed. Someone else can interpret how the change in these
ratios
will change the way your jag drives and accelerates.

Gearbox Ratios

MKV, MKVII, XK120, XK140, XK150

1st 3.375.1

2nd 1.982.1

3rd 1.367.1

4th 1.1

XK120, XK140, XK150 close ratio when fitted

1st 2.98.1

2nd 1.74.1

3rd 1.21.1

4th 1.1

MK2 2.4 litre

1st 2.67

2nd 1.74

3rd 1.25

4th 1.1

3.4 / 3.8 MK2 / S Type, 4.2 MKX, 420, E Type 4.2 2+2

1st 3.04

2nd 1.97

3rd 1.32

4th 1.1

E Type Series 1 3.8 Coupe /Roadster

1st 3.377

2nd 1.86

3rd 1.283

1st 1.1

close ratios

1st

E Type Series I 4.2 Coupe / Roadster

1st 2.68-1

2nd 1.74-1

3rd 1.27-1

4th 1-1

XJ 2.8 / 4.2, E Type Series II and V12 E Types

1st 2.933.1

2nd 1.905-1

3rd 1.389-1

4th 1-1

Overdrive on XK140 / XK150, MK1, MK2

Overdrive .779

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

1 Jul 2007 10:53:33 +0200
From: “Ken Green” ken.green@kgcc.co.uk
Subject: Re: [xk] Gearbox options

The gearbox ratios for the overdrive boxes were the same
(there was also a close ratio version but that’s not
dependant on having an overdrive). With the overdrive fitted
Jaguar changed the default rear axle ratio.

For the XK150 without overdrive the normal axle ratio was 3.54:1

With the overdrive the ratio was 4.09:1 giving an effective
3.19:1 ratio with the overdrive engaged.

I found the gearbox ratios for 120 moss box as:
first 3.375
second 1.982
third 1.367
top 1
does anyone know if the moss box with overdrive is the
same?

Does this help?

http://www.jag-lovers.org/xk-lovers/library/gearbox_reilly/moss_gearbox_identification.html

Rob Reilly - XK120 FHC 679187

Yep.

All we need is this list aligned with Gearbox Ratio data, with a few
additions like “EExxxx”, “EJSxxxx” “KExxxx”, “KJxxxx”, “KJSxxxx” and
“KLxxxx” for those looking at all-synchro upgrades for existing Moss
box.

Roger Payne
PO Box 32
ERINDALE CENTRE
A.C.T. 2903
Australia-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf
Of R&J_Reilly
Sent: Tuesday, 3 July 2007 1:44 AM
To: XK mailing list
Subject: RE: [xk] Gearbox Ratios

Does this help?

http://www.jag-lovers.org/xk-lovers/library/gearbox_reilly/moss_gearbox_
identification.html

Rob Reilly - XK120 FHC 679187

In reply to a message from Terry McGrath sent Mon 2 Jul 2007:

All

Can a Moss GBN(MKI/II) close ratio box be used in a 140?–
John McM XK 140 DHC 807003
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from khyber sent Wed 4 Jul 2007:

Sorry the second part to that question is. If the GBN will not go
into the 140 easily is it worth buying one for parts given how hard
it is to get parts for moss boxes esp with the overdrive?

Regards–
John McM XK 140 DHC 807003
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from Terry McGrath sent Mon 2 Jul 2007:

Hi Terry,
I am in the midst of deciding what non-OD gearbox to put in my 120.
It currently has an E-type S1 gearset (I think) in its original
casing. Internals are not in a good condition.
I have found a good GB box from a Mk1 and a CR box from a 140.
These are my alternatives. I have a late rear axle where I can
change the diff ratio as part of the overhaul.
Do I read you correctly in saying that the CR gearset is ideal with
a 3.07 diff?
But then you said that I�d get the same or similar result with the
GB box from a Mk1.
Did I understand you correctly?
(I can also buy a good condition GBN box from a Mk2 (1962) but this
will have had harder work in its heyday, I imagine)
All the best,
Peder–
The original message included these comments:

First gear is way to low for an XK ie 3.375 the CR ratio is much nicer at
2.98 but if you drop a set of 2.4 MK1 / MK11 non synchro gears hey presto
you have a very usuable first gear at a price a lot less than finding an XK
CR gearbox. Even MK2 3.4 etc is an improvement and is very close to CR ratio
Gearbox Ratios


peder
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

In reply to a message from peder sent Wed 19 Dec 2012:

Looking forward to any suggestions around this topic…–
The original message included these comments:

I am in the midst of deciding what non-OD gearbox to put in my 120.
I have found a good GB box from a Mk1 and a CR box from a 140.
Do I read you correctly in saying that the CR gearset is ideal with
a 3.07 diff?
But then you said that I�d get the same or similar result with the
GB box from a Mk1.


peder
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Peder,

I have a 3.07 rear end in my 120. It is a huge improvement over the 3.77
rear end that was in the 2HA axle. I was really fortunate to track down a
4HA rear axle and swapped the gearset in that. It was then a matter of a
weekend axle swap. My personal opinion is that you would be better with the
stock gearbox ratios. If you compare them using a gearing calculator
available on many websites (check my previous posts for some sites), you’ll
find that the stock gearing with a 3.07 rear end is very close to the CR
gearing with a 3.54 rear end from 1st through 3rd and 4th is the equivalent
to a .87 OD, IIRC. Again, see my posts from a few months ago. I put some
detailed charts together.

Here are the comparable ratios 4th to 1st, adjusting for the difference in
the rear axle (Ratio@rear = 3.07/3.54 x Ratio-gearbox):

CR w/ 3.54 1 1.21 1.74 2.98
Std w. 3.07 .87 1.19 1.72 2.93
CR w/ 3.07 .87 1.05 1.51 2.58

I think the toughest number is the equivalent of a 2.58:1 ratio for first
with a 3.07 and CR gearbox. I think it will make it very hard to get moving.
Notice that the standard gearbox with the 3.07 is a little higher geared
than even the CR box with the 3.54.

“Mark 1” Mark Stephenson Phoenix, AZ
52 XK120 S673129; 59 Mark 1; 84, 85, 86, 95 XJ6-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
peder
Sent: Saturday, December 22, 2012 7:05 AM
To: xk@jag-lovers.org
Subject: Re: [xk] Gearbox Ratios

In reply to a message from peder sent Wed 19 Dec 2012:

Looking forward to any suggestions around this topic…

The original message included these comments:

I am in the midst of deciding what non-OD gearbox to put in my 120.
I have found a good GB box from a Mk1 and a CR box from a 140.
Do I read you correctly in saying that the CR gearset is ideal with a
3.07 diff?
But then you said that I´d get the same or similar result with the GB
box from a Mk1.


peder
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]-- --Support
Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Roger Payne

I’m still interested in the list of all synchro ratios

is there one anywhere?

best i can do is the

EJ xx (Early 4.2 E)boxes 2.68, 1.74, 1.27, 1, R 3.08
KE xx/ KJS (4.2 E later - all types) 2.933, 1.905, 1.389,1, R 3.378

These ratios same as V12 E-type and 2.8/ 4.2 XJ

XJS 3.328, 1.905,1.389,1,R 3.428 (these may also be the same as 3.4 series 2 XJ)

I have now found the S-type 3.4 and 3.8 - later cars natch. Also 420

3.04,1.973,1.328,1 R 3.48

2.4 litre ie 240 synchro ratios I believe ill be very different certainly first gear

Russell…
There is LOGIC in all Jaguars Gearbox Number is within the prefix LETTER CODES…

The first letter denotes the RATIOS
So first letter “E” as with EJ (4.2 E-type OTS/FHC), EJS (4.2E 2+2) and EE (a few only S1.1/2 OTS/FHC) have ratios 2.68:1 (1st gear), 1.74:1 (2nd gear), 1.27:1 (3rd gear), 1.00 (4th gear), 3.08:1 (Reverse)

Then later E-types with first letter “K” as with KE (last of S1.1/2E and all S.2E OTS/FHC), KJS (S1-1/2E and all S.2E 2+2), KL (V12E OTS and 2+2) and later saloons KF and KFN (XJ6 without and with overdrive) and KZ and KZN (420G without and with overdrive) have ratios 2.933:1 (1st gear), 1.905:1 (2nd gear), 1.389:1 (3rd gear), 1.00 (4th gear), 3.378:1 (Reverse).

And over same period the various Saloons that offered all-syncro manual gearboxes and also with an overdrive option, denoted by third letter N
So first letter “J” as with JB and JBN (S-type 3.4 and 3.8), JC and JCN (Mark 2 2.4, 3.4 and 3.8), JD and JDN (420), JZ and JZN (4.2 Mark 10) have ratios 3.04:1 (1st gear), 1.973:1 (2nd gear), 1.328:1 (3rd gear), 1.00 (4th gear), 3.49:1 (Reverse). Some of these gearboxes are extremely rare, as are manual gearboxes fitted to Daimler V8-250 and Sovereign.

But please note the first letter only denotes the RATIOS, with the various second letters and sometimes third letters denoting other things that affect interchangeability of internal gears and mainshafts - so don’t think about mix and match unless you know exactly what you are doing…

Thanks Roger
There are also the 3.4 xj series 2 (and xjs) boxes with ratios 3.238,1.905,1.389,1 R 3.428

At first I couldn’t imagine why a 2.4 Mk II would have a higher 1st gear ratio (2.67) and a 3.4 or 3.8 etc would have a lower one (3.04). Then I realised that the 2.4 probably would have a very low diff ratio. It would be interesting to have the list of models with gear ratios and axle ratios, so overall gear ratios could be compared.

2.4 litre car has diff ratio of 4.55 versus 3.4 and 3.8 at 3.54 also the
2.4 revs higher?

Makes sense. And I suppose the overdrive cars are maybe different again?

You would also need to factor in the effect of the tire size. A smaller tire radius lowers the effective drive ratio. Is it the 420 that uses 1" wheels? That 14" tire would lower the effective gear ratio.

The 420 is on 15" wheels, but the Mk X and 420G use 14".

1 Like

Does anyone know the torque capability of the all-synchro gearbox?

Hi again Roger

I’m getting close to fully understanding these gearbox numbers

The ‘missing’ ones have a 3.238 first gear and were used in early V12 XJS, 3.4 series 2 XJ6 and 4.2 XJ6 after engine number 8L22647 (Nigel Thorley’s book suggests the change was late 1975- but the reference is mixed up with V12 information and has a typo)

Do you know the letter prefix for these boxes?