View Full Version : TR6 TR3 VS TR6 Transmission units

10-24-2006, 08:11 AM
I have 71 TR6 and the transmission is starting to need rebuilding, jumping out of 3rd on deceleration, My delima... I found a TR3 transmission with A type overdrive, owner says its been rebuilt but never installed it. My transmission is non overdrive but I would like to upgrade to OD unit Is there any internal difference between a TR3 and TR6 Transmission, Like better bearings, thrust washers,syncros? the price is great but If I send mine to quantumechanics I am talking 2500 to rebuild and add OD and the wiring to convert. I am not considering a 5 speed conversion

10-24-2006, 08:45 AM
The TR3 tranny does not have syncro in first gear while the TR6 does. The input shaft on the TR3 tranny is bushed while the TR6 one has bearings. The bigger killer though is the starter on the TR3 was a short nose and the one on the TR6 was a long nose. The result is that you can't fit the TR6 starter into the houseing of the TR3 tranny. The short answer is you may not be able to perform a simple swap.

Having said all that, I love the overdrive. I had the same option as you last summer and I ended up putting the TR3 guts into my TR4 tranny case just so I could have overdrive. It was a lot of work but worth it in the end.

10-24-2006, 09:17 AM

You could remove the tailpiece extension from your TR6 gearbox case and stick the overdrive unit from the TR3 on there. Unfortunately, you would also have to swap mainshafts, too. I can't remember the year that TR6 boxes changed their mainshaft and mainshaft bearing design--my suggestion would be a lot easier with the earliest possible TR6 gearbox. It's been a while since I did all of my research, so hopefully someone will jump in and correct me if I'm wrong. No matter how you slice it, you would be rebuilding a gearbox. If I did it (five years on the road, yay!), anyone can do it. TRF's parts manuals--available free with orders--are a valuable resource for understanding compatibility issues with engines, gearboxes, diffs, etc.

Or, you could sell the TR3 gearbox/overdrive in your possession and apply the funds to a TR6 trans w/overdrive.

Whatever you decide to do, good luck.

10-24-2006, 09:38 AM
That is what I did. If you change the input shaft (which you will need to do in order to put the TR3 overdrive on there) you will also loose the first gear synchro (as I did). In the long run I was happy with the trade off of loosing synchro and gaining overdrive.

Geo Hahn
10-24-2006, 01:27 PM
...The bigger killer though is the starter on the TR3 was a short nose and the one on the TR6 was a long nose. The result is that you can't fit the TR6 starter into the houseing of the TR3 tranny...

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I think that problem will only occur if the gearbox is from a pre-TS50000 TR3/3A.

Even if it is a pre-50xxxx it should be pretty easy to get around this by using one of the new Hi-Torque Starters. I believe they are all 'short-nosed', e.g. they don't care about the bulge in the bellhousing. You would have to use the one that is correct for your flywheel.

Some have also used the long-nosed starters on the early TR3A gearboxes by punching a hole in the bellhousing.

Geo Hahn
10-24-2006, 01:36 PM
Hey... after that posting I decided to see what was out there by Googling for Triumph overdrives. Found an ad from a fellow with a TR4 gearbox & overdrive for $250 and a TR3 gearbox & overdrive for $150.

Had my 400 bucks ready when I figured out I was looking at the classifieds in the TSOA Newsletter for April 1978.

10-25-2006, 07:16 AM
thanks for all the information, I think I will just spend the money and have my transmission rebuild and add a J type overdrive from John Esposito