TR4/4A Can I put a TR3A Clutch in a 4A?

[karls59tr]

I seem to have ended up with a couple of still good TR3 clutch assemblies on my parts shelf. Is it possible to use one of these on a TR4A I'm working on? I realize that the 4A calls for a different clutch but the transmissions are basically the same. Years ago I put a TR6 trans in my 3 and I believe I used the 3 clutch set up so it should be doable?

 

[martx-5]

I believe you'd have to swap over the flywheel from the TR3 also, as the bolt pattern for the pressure plates are different.

 

[DanB]

Is the clutch disk the same?

 

[karls59tr]

Actually I havent pulled the 4A clutch yet to compare disks but I do have a spare 3 flywheel if needed. It's too cold up here to work on the car so I'm just gathering info on 4A restoration for when the weather breaks.

 

[Marvin Gruber]

Clutch and flywheels will have to stay matched up. The trans you can swap around.

Marv

 

[karls59tr]

Is it pretty strightforward to swap out the 4A flywheel for the 3 flywheel? Same bolt pattern so just take one off and put the other on?...no other issues?

 

[martx-5]

Yes, I went the other way...I put a TR4A flywheel and clutch assembly in my TR3.

 

[PeterK]

If you change from a TR4A diaphram pp to the 3-finger design, you will also have to cut down the gearbox shaft extension cover from 2-3/8" to 1-31/32". Moss p/n 848-000 for reference.

 

[DanB]

If you change the flywheel will you need a different starter?

 

[TR4nut]

The starter might be an issue, if the flywheel is off an early 3 - but later 3A flywheels would just be a bolt on.

 

[karls59tr]

Randy So would I have to use the 1&31/32 extension cover for a 3A flywheel as Peter mentioned? I have a TR6 trans on the car and cant remember if I changed extension covers. I'll have to check when I get there. So the ring gear on the 3A flywheel will mesh with the 4A starter gear?

 

[TR4nut]

I'm not positive but I think you need the shorter extension cover Peter mentions only if you use the 4A diaphram clutch - it doesn't have to do with the flywheel. Since you are using the older fingered clutch I think you can get away with both long and short versions.

A late 3A flywheel will work with the 4A starter - same starter as on a TR4. I think if its bolt on ring gear you are fine. If Press on, check it you may be in trouble.

 

[TR3driver]

Right, the shorter front cover is for the TR4A-TR6 diaphragm clutch.

Don't forget that the throw-out bearing and its carrier are different too.

Change point for the flywheels and starters was at TS50000. If your flywheel is earlier, you'll need the early starter to match it. Watch out for interference with the exhaust system, I've heard that the TR3 (earlier) starter hits the exhaust manifold on a 4A. Or if you have a gear-drive starter; you can just change the pinion gear to the smaller one for the early flywheel and not worry about the exhaust.

The clutch disc is not the same, but you may be able to get away with using the smaller TR4A disc with the larger TR3A flywheel & pressure plate.

 

[TR4nut]

Watch out for interference with the exhaust system, I've heard that the TR3 starter hits the exhaust manifold on a 4A.

That might be an issue if you have the early bomb style starter, but for the later post 50K TR3A cars there is no issue, starter would be the same from late 3A through 4A.

edit: oops reread Randall's note and see he knew that already. the thing to worry about is if it is an early starter..

 

[PeterK]

And with the help of a few friends, all this can be done stranded on the side of a road (with the promise of a payback brew or 2.)

The beauty of TRs.

 

[karls59tr]

That's stretching it a little.... but there is a certain amount of satisfaction in being able to repair most breakdowns of an old TR at the side of road unlike modern cars.

 

[HerronScott]

I can attest to changing the clutch in my wife's 68 Spitfire on the side of a road. Didn't help that it started to rain but luckily it was near the end so we were mostly in the car at that point.

Scott