Possible to fit later 4.2 gearbox to 3.8 E-type?

[AFC1886]

Hi chaps, just wondered if someone could tell me is it possible to just bolt on a later 4.2 all synchro gearbox on a 3.8 engine? I want to replace my moss box for one, and side by side they look almost identical in length, bellhousing/shaft etc the same. If not what modifications would i need to make? Would i need to use the 9 1/2" clutch instead of 10? Anything else?

Any help much appreciated, thanks!

[tiggerjaguar]

Not full answer im afraid but maybe some guidance.
Its possible swap and has been done many times, but its not just a straight swap over. from memory you need the matching flywheel.

for a much better and complete answer why not log on to the forum at the etype club. you can access through the etype uk web page. your answer may be in the archives or ask a question.

[jith]

AFC1886 said:

Hi chaps, just wondered if someone could tell me is it possible to just bolt on a later 4.2 all synchro gearbox on a 3.8 engine? I want to replace my moss box for one, and side by side they look almost identical in length, bellhousing/shaft etc the same. If not what modifications would i need to make? Would i need to use the 9 1/2" clutch instead of 10? Anything else?

Any help much appreciated, thanks!

The external dimensions are almost identical. The main difference is the flywheel and clutch assembly. The 3.8 has an inertia starter motor with a different number of teeth than the 4.2, which has pre-engaged starter. The clutch assembly has a spring driven pressure plate, whereas the 4.2 has a 9.5 or 10 inch diaphragm clutch.

In other words, to do the conversion properly you will need the gearbox, a flywheel, a diaphragm clutch kit, a pre-engaged starter, and the appropriate slave cylinder for the 'box.

I suggest you have the flywheel skimmed while you're about it, because it frees up a few horses and makes the engine so much more tractable.

If you get stuck PM me and I'll send you some pics of a 4.2 I did last year.

J

[a8hex]

Or if you fancy pushing the boat out, Guy Broad have a 5 speed box setup as a replacement for the Moss box, internally it uses Ford MT75 parts in a custom casing. Certainly makes changing much easier* than the old Moss box

(* easier, now I need to work out whether that equates to better)

[V8 FOU]

I have an XJ6 gearbox knocking around somewhere if you are interested...

[AFC1886]

Thanks for the replies chaps! Side by side they both have a hydraulic piston slave cylinder, the 4.2 is just bigger? So is it not possible to just fit my 3.8 flywheel with a 3.8 10" clutch? I have a pre engaged starter and the 3.8 clutch fits over the 4.2 spline perfectly? The gearbox i have is from a S2 car if they are in anyway different from an S1.

Best regards,
Henry.

Edited by AFC1886 on Monday 30th July 18:16

[jith]

AFC1886 said:

Thanks for the replies chaps! Side by side they both have a hydraulic piston slave cylinder, the 4.2 is just bigger? So is it not possible to just fit my 3.8 flywheel with a 3.8 10" clutch? I have a pre engaged starter and the 3.8 clutch fits over the 4.2 spline perfectly? The gearbox i have is from a S2 car if they are in anyway different from an S1.

Best regards,
Henry.

Edited by AFC1886 on Monday 30th July 18:16

The diaphragm clutch is far superior to the old spring type. You will find it lasts longer and is lighter on the pedal; well worth the change. There's no difference in the 'boxes between S1 and 2.

J

[Jagmanv12]

I've done several gearbox changes so can give you the following info.

The flywheel, bellhousing and starter motor must be from the same model - i.e. these 3.8 parts must be used together and likewise 4.2 parts. So 3.8 bellhousing with inertia starter motor and 104 tooth flywheel. 4.2 bellhousing with dowels to locate pre-engaged motor and 133 teeth flywheel.

A larger clutch is a good idea but not all flywheels are drilled for the larger size, although of course you can have it done.

I've got a bellhousing and some flywheels if you need one.