The 'E' Type Forum

I want to change a 3.8 moss gearbox to a 4.2 4sp synchro E type gearbox.
The idea is to retain the 3.8 bellhousing, starter and flywheel.
The bits have not turned up yet.
Am I correct in assuming the 3.8 bellhousing will bolt onto the 4.2 4sp synchro gearbox?
Or have I got more fettling to do?

Hi James....depends on the 3.8 bellhouseing......the bellhouseings have a circular recess on the rear face...its larger on the 4.2 bellhouseing to accommodate the larger front bearing seal on the 4 syncro gearbox(just over 4.25in dia)....however some 3.8 bells from S types etc that had an all syncro box have the larger cutout.....also you can find that a previous owner may have machined a standard 3.8 bell to accept a 4 syncro box....Steve

James : you can get into all kinds of difficulty if you attempt this. The problem lies in the fact that the 3.8 and the 4.2 have different sized flywheels and starter motors and AFAIK these have to be fitted in matched sets. I suggest you research the archives on this board which will give you an idea of the problems encountered, including by me!

Hi Christopher it really isnt difficult to mix and match parts.....some of the usual suppliers now even sell starter's to make it easy....eg fits a 4.2 bell but with a pinion to fit a 3.8 flywheel and visa versa......you just need to go into with your eyes open and research a bit.....yes iv done it on a few builds now.....Steve

Did the swap (helped) with my BMC mechanic friend.
4.2 bellhousing, breather, 4.2 flywheel machined/lightened to 3.8 specs, 4.2 clutch, 4.2 driveshaft, gear reduction starter with no spacer.

Thanks for all that.

I took the whole lot out today and split the 3.8 engine from the gearbox, so I shall check the bellhousing to see what I have got.

I suspect it is all as was assembled by Mr Lyons, as the numbers are correct and the car was parked up in the late 60s when it was 8 years old.

Whatever happens I was going to keep the original gear box with the car. Possibly just not fitted to it.

I have a good 4 speed synchro gearbox as well, with no bellhousing attached.

So I shall start measuring.

politeperson wrote: ↑

Sun Nov 19, 2023 4:51 pm

I have a good 4 speed synchro gearbox as well, with no bellhousing attached.

So I shall start measuring.

I have an all synchro box in my 3.8 coupe. I bought it without a bell housing.

I machined a Moss box bell housing to fit that box, and fitted it with the 3.8 flywheel and a 3.8 hi torque starter. It all works.

https://www.youtube.com/watch?v=uNFfRA3S_uM

Had I had an all synchro bell housing I would have used it, and I reckon it would have worked.

Thanks for that.
Yes, I was hoping to be able to use what I have, in other words the 3.8 bellhousing and flywheel.
Machining is no problem, as long as I know what I am machining it too.

I gave a 4.2 bellhousing away about 2 months ago!, never mind.