TR4A clutch on TR3A flywheel?

[jbenajes]

Hello,

 

What kind of machining must be done to the TR3A flywheel to install a TR4A diaphragm clutch cover?

 

Is the bolt pattern of both covers the same?

 

Thanks for your time and answers.

 

Jesus

[peter clarke]

TR3A cover mounts on 10 5/8" PCD and TR4A mounts on 9 7/8" PCD therefore not compatible. Easy to drill and tap new holes but critical that they be concentric. Need to install new locating pins and worth getting cover and flywheel balanced as an assembly.

[jbenajes]

Thanks, Peter, for your quick and precise response.

 

As far as I know this is the least difficult way to convert to a diaphragm clutch, isn’t it?

 

Jesus

[Bob Smith]

Jesus,

The other option is to use a Stag Clutch Cover and driven plate. Stags used a 9" plate same as non diaphragm clutch TR. The dowels on the Stag flywheel are spaced at 0/120/240 degrees so you will need to drill 2 additional holes at the Correct P(itch) C(ircle) D(iameter). The original dowel at 0 degrees suits either application. The existing dowel position at 180 degrees does not interfer with the new clutch cover. Dont forget that you need to modify the clutch release bearing and sleeve to suit the revised application.

[Dave Larnder]

Jesus: Feliz Año Nuevo

I remember when I considered making the conversion, but was advised against it either on this forum or others owners or maybe even by TR Bitz, as the standard clutch is more than adequate for the job and not worth the bother and expense. I do however agree that the flywheel (either lightened or standard) should be balanced with the cluch, mine was, and by the balance marks on it, there was quite a bit of out of balance weight so it is important.

 

Dave

 

[jbenajes]

Thanks Bob and Dave for your useful advice.

 

When I restored my TR3A, I only refurbished and adjusted the original coil spring cover. But now a friend here in Valencia needs to repair the clutch in his TR3A that he uses mainly for rallying, and since I have a left new TR4A cover, we were toying with the conversion.

 

Jesús

[Ashley James]

I've got two engines here, both modified to take the 4A Spring diaphragm clutch and lightened and balanced, but I'm not sure of what difference it made. However I'd always get a flywheel and clutch balanced together if I replace a clutch because the difference in smoothness is considerable.

[peter clarke]

If you use the 4A cover you will need a new TR4/6 smaller dia friction plate and the rounded release bearing to suit. (stick with what you have as do not see any advantage in changing.)

[Alec Pringle]

Hi Jesus,

 

the later diaphragm clutch is of significantly higher clamping force than the sidescreen spring clutch - the later clutch is not necessary for the lower power and lighter weight of a standard sidescreen car in normal useage. However, if your friend has an uprated engine and is using the car in competition then an uprating to the later clutch sounds like a jolly good idea to me, and preferably the stronger (greater clamping force) TR6 assembly rather than the 4A specification, B&B rather than Laycock.

 

The original sidescreen clutch assembly is short lived in rally useage, I found that out more than 40 years ago after destroying 3 in 6 months in a 3A, along with a couple of clutches in a Triumph 2000 saloon - replacement in both cars with the then new TR6 assembly and no further problems . . . .

 

Cheers,

 

Alec

[TR 2100]

Agree with Alec.

 

Also, the later clutch, as standard, is lighter than the

original clutch and, due to the manufacturing process

I think, tends to be far better balanced as new.

(although I am basing my comment on much older

stock clutches).

When I rebuild my first TR4 engine, and had two clutch

assemblies balanced with the crankshaft/flywheel assembly

for future use, neither clutch required any balancing work)

 

AlanR

[TR 2100]

The original sidescreen clutch assembly is short lived in rally useage, I found that out more than 40 years ago after destroying 3 in 6 months in a 3A, along with a couple of clutches in a Triumph 2000 saloon - replacement in both cars with the then new TR6 assembly and no further problems . . . .

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

That reminds me of the classic advice, given to one Len Bosshard,

who wrote in to the Technical Secretary (Pete Cox at the time?)

complaining that he had gone through so many clutches and

gearboxes in a short time, and asked for advice.

 

The advice given - "try using the spare pedal on the left".

 

AlanR

[Andrew Smith]

.......................the later clutch is not necessary for the lower power and lighter weight of a standard sidescreen car in normal useage.

 

Hi Jesus,

 

Whilst Alec is correct and the conversion is not necessary for normal road use, the TR6 ( B&B ) diaphragm clutch conversion does make the pedal action much lighter, particularly useful in heavy traffic - TuRK has the diaphragm clutch conversion fitted for the last 10 years (approx 40,000 miles) without any issues. A worthwhile job in my view and I have no intention of rallying TuRK..................

 

If I remember correctly and depending on the year/TS number of your friend’s 3A, you may need to replace the flywheel ring gear from the shrink-on type (early 3A up to TS 50000) to a bolt-on type as per later 3As (from TS50001), 4 and 4A and also turn down the clutch extension sleeve by 3/8" to 2", or buy a 2" repro.

 

Cheers

Andrew

Edited January 3, 2013 by Andrew Smith

[billg]

Hi Jesus,

 

I am on the same sort of road as yourself. I recently bought a Triumph

2000 A-Type OD gearbox to fit in my newly restored

1959 TR3A ch no in the 55,000's.

 

I have bought a spare TR3A flywheel with bolton ring gear

Plus also. a GT6 clutch cover and plate

I have been quoted about £200 to have this flywheel

Flywheel lightened, re drilled and balanced.

 

I am just about to go ahead on this project but

The A-type OD box has other issues once rear mounting

Modification, solenoid mounting casting change

So the whole thing is more complicated than I wanted it to be.

But then why should life be easy!??

 

Hoping to do this before Malvern, but next week starting off the

Same ramp as the Historic Monte Carlo Rally from Glasgow

On the 26th January from Glasgow Green. Will post

Pics after that. Some brave souls are following the rally cars all the way

To Monaco!! Perhaps next year? If Glasgow can retain the start

 

See the Caledonian Classic and Historic Motorsport Car Club site

For more details.

 

Regards

 

Bill G @ NB

 

Ps it will be a longer drive for me to get to start ramp

Than the langur of the Rally to Luss! Looks to be a night rally

So that will be different