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Brinkerhoff
05-13-2011, 12:17 PM
I have a 74 TR 6 that I would like to know if I can fit the earlier overdrive gearbox to . Is this straightforward? The car did not come with overdrive.

TR3driver
05-13-2011, 01:27 PM
Should be fairly easy, I think. The early OD used the same rear mount as the non-OD, so that should be OK. Driveshaft and clutch are the same, so they'll mate right up.
You'll need to do something about the speedo drive ratio, and perhaps cut the trans tunnel to clear the angle drive.

YYCDave
05-13-2011, 07:17 PM
You should be aware that starting in '73 Triumph changed fromm the earlier A-Type (OD on 2-3-4) to the J-Type overdrive (OD 0n 3-4)which uses different rear transmission mounts. If you want to use an A-Type on your '74 you'll need a conversion kit which I believe is available from Quantum Mechanics. Well worth it though as OD transforms the character of the car.

tdskip
05-13-2011, 07:37 PM
+1 on this being worth the effort.

BRSLimited
05-13-2011, 08:28 PM
IMO, if you have an early A type overdrive that is good you might consider selling it and buying the later J type which was a little more reliable anyway. Working A types bring a premium from people with TR3's and 4's that want to put overdrive in. J types seem to be more common and don't go quite as high price wise.

TR3driver
05-13-2011, 08:48 PM
You should be aware that starting in '73 Triumph changed fromm the earlier A-Type (OD on 2-3-4) to the J-Type overdrive (OD 0n 3-4)which uses different rear transmission mounts. If you want to use an A-Type on your '74 you'll need a conversion kit which I believe is available from Quantum Mechanics. Well worth it though as OD transforms the character of the car.

I could be mistaken, but I don't believe a conversion is necessary to fit an A-type OD to a later TR6 that did not have OD originally. Although the J-type does mount differently; and the later rear crossmember, etc. were different; I believe the A-type mounts the same as the later non-OD gearbox. So the appropriate mounting brackets will already be on the car.

TR3driver
05-13-2011, 08:50 PM
J types ... don't go quite as high price wise.
IMO there is a good reason for that. I drive both, and IMO the A-type is much "sportier" than the J-type.

So much so, that I even tried to get a Stag A-type imported from the UK, after installing a J-type. Unfortunately it never arrived (and Stag A-types aren't quite the same as the ones used on TRs).

DougF
05-13-2011, 11:07 PM
I owned a '74 non overdrive car before my '72. I dropped an A-Type OD in with absolutely no problems. I like the A type with the greater flexibility in 2nd, 3rd, and 4th. Though there isn't much difference between 3rd OD and 4th. Will it detract from the value of the car? No. Personally, if I sell my TR6, the OD is coming out and will go into the next car I buy.

Brinkerhoff
05-13-2011, 11:40 PM
Thanks to all . I'll pursue this further. I agree it makes a big difference as I've had them both ways.

vettedog72
05-14-2011, 06:17 PM
I sure like the idea of getting the RPMs down for both MPG and longevity of the motor.The stock differential ratios for the non OD cars are numerically lower (than OEM OD cars) so you really get even more advantage with the OD addition.

TR3driver
05-14-2011, 07:01 PM
The stock differential ratios for the non OD cars are numerically lower (than OEM OD cars)
I don't believe that is correct, for the TR series. Rather, the optional 4.10 gears were only available in conjunction with overdrive. But just ordering an overdrive would still get you 3.70 gears (or 3.45 if the engine was fuel injected).