TR6 Couple of Tr6 related questions

[oxendine]

What size Su's will fit and perform properly on the Tr6? I have a J type overdrive unit. What is the procedure to fit this unit to a non overdrive transmission?

Thanks

 

[DNK]

What year car?

 

[oxendine]

Sorry, 1972.

 

[AltaKnight]

Why do you want to change the stock ZS's for SU's?

 

[TR3driver]

Fitting a J-type to a 72 is a major undertaking. The gearbox will have to be almost completely disassembled (might as well do the whole job while it's apart), and then you'll need a mainshaft that matches both the gearset in the gearbox, and the overdrive. I'm not certain offhand, but ISTR you have to order a custom-made shaft to mate a 72 gearset to a J-type. You'll also need to strip the shift cover, to drill & tap it for the funky metric threads for the lockout switch.

Most likely, you'll also need to disassemble the OD and replace the speedo drive gears with a ratio suitable to your speedometer. Another alternative is to have a ratio adapter made to suit. But frankly I'd want to strip and examine the OD anyway, even a "working when removed" unit can have serious internal problems that are much better to find now rather than after it's in the car.

Then you'll have to cut the frame, and create a new rear mount for the OD. One successful method is described at
https://www.buckeyetriumphs.org/technical/jod/AdaptingJOD/AdaptingJOD.htm

HS6 SUs seem to be a popular choice, but you'll still need to get suitable needles and springs. Depending on the carbs, there is also some work required for linkage, I believe.

 

[YYCDave]

You'll want SU HS6's that are essentially a bolt-on with an appropriate throttle linkage. These are 1 3/4" throats.

 

[DNK]

Shameless Plug

 

[oxendine]

I guess I'm a little confused as to the fitting of the overdrive unit to a Tr6 transmission. I bought the unit from a forum member who said it was from a TR6. I thought or maybe wished it would be as simple as bolting it to the transmission?
Seems I'm wrong?

 

[TR3driver]

The overdrive changed a great deal in 1973, from the earlier A-type to the J-type. Although the overall operation is similar, the J-type is very different internally (ISTR one of the bearings is the same, but everything else is different). The mountings, speedo drive, mainshaft etc. all changed at that time as well. The J-type uses a much longer adapter, so its body sits much farther back in the car (hence the cuts to the frame to mount a J-type in an earlier TR6).

But even installing an A-type is not as easy as just bolting it to the transmission. The mainshaft still has to be changed from the long non-OD version (which runs all the way through to the rear flange) to the short OD version (which ends at the overdrive gears), and the countershaft has to come out in order to remove the mainshaft.

And you still need the lockout switches (two of them for an A-type) on the top cover. Backing up with overdrive actually engaged does some serious damage to the unit, so the lockout switches are essential to prevent it from being engaged in reverse.

 

[tdskip]

Did you buy the whole transmission or just the overdrive unit? Sounds like the later. Pretty common to do that with an idea you can just bolt it on, but not the case. Randall nailed it.

On a '72 might be best to just sell that unit and take the money and put it towards a correct A-Type.