View Full Version : TR2/3/3A TR3 Transmission Questions

03-03-2008, 12:03 AM
I am gettign ready to pull my trans and do a clean up, new seals and look for any bad parts. How hard are they to rebuild?

I also have a chance to buy a rebuilt TR6 trans and they guy is telling me it will fit a TR3. Does anyone have experiance swapping out a TR3 trans for a another or newer model? Also does the TR6 trans have a syncronized 1st gear?

03-03-2008, 07:45 AM
Curt, they're not hard to rebuild, or so Im told. but you have to do it step by step and need some special pullers. I'm getting ready to start mine. I have a step by step manual that I downloaded from a fellow who is a member of the Ohio Buckeye Triumph club. It is an excellant step by step manual complete with pictures and ways to build the special pullers.

I downloaded it from their website. You might look it up:
www.buckeyetriumphs.org (https://www.buckeyetriumphs.org)

I had heard that because of liability problems they stopped offering it. If so I don't mind copying what I have and sending it to you. I also have his tech manual on the overdrive. Members name is Nelson Riedel. He might even be on the forum for all I know.

Regards, Tinkerman

Geo Hahn
03-03-2008, 10:44 AM
As you note, they were off-line for awhile but now they're back --


Good stuff.

03-03-2008, 11:06 AM
Just finished putting an A type over drive off of a TR3 transmission on to a TR4 non-overdrive. This required changing the main shaft. I wanted the full synchro option with the OD.
The transmissions are not difficult, the difficult part is making sure the shims go back in the original place or putting the proper amount in between the gears. Too much and not enough spacing will make the synchros not work properly. You have to assemble the transmission to check the spacing.
Another part I found to be difficult was removing the clip on the main shaft. It requires a special tool and if you don't have it then the clip is a pain to remove. Plus the clip needs to be replaced every time it is removed. It is a "C" clip (not the ones with the holes for the clip tool).
If you like you can phone me (859) 608-9167 and I'll give you some pointers.

03-03-2008, 11:15 AM
Curt, I swapped a rebuilt TR6 tranny with A type OD into my TR3 a number of years ago. The shorter TR6 input shaft must be replaced with the TR3 input shaft to engage the pilot bushing and the rear tranny mount bolt holes may need to be elongated. Well worth the money and effort.

03-03-2008, 12:34 PM
Depending on which TR6 box you are looking at, the longer TR3 input shaft will not mesh properly with the other gears. I forget the change point offhand, but that was the case with the TR6 box I put in TS39781LO. However, the shorter shaft (and a new pilot bushing) seemed to work just fine for me.

Pre-50K TR3/A will require some massaging of the transmission tunnel to clear the starter bulge. You'll also lose that nifty dipstick (unless you rebuild the TR3 top cover to fit the TR6 box as I did). Swapping gearshifts may be a problem if you keep the TR6 cover as some of them used threaded pins instead of the through-bolt, but you could probably drill for the bolt.

Again depending on the vintage of TR6, you may need to replace the 3 studs between the engine block and gearbox. The gearbox front flange got thicker over the years, requiring longer studs.

If you are keeping a TR3 clutch, you might want to swap over the longer TR3 front cover. I eventually went to a 4A clutch & shorter front cover which worked fine for me, but it seems a lot of TR6 folk have problems with that short cover so I'd keep the old one with the old clutch.

As noted, the TR6 trans does have synchromesh in 1st gear, plus a slightly higher ratio (which makes it much more useful IMO unless of course you are pulling stumps <<GRAEMLIN_URL>>/grin.gif ) You will have to elongate (or just drill new ones that touch the old ones) the holes in the rear crossmember, where the motor mount bolts to it.

Late TR6 will have the wrong speedometer drive gear. Don't know offhand if the TR3 gear will fit and be correct or not (I used a TR4 OD which neatly ducked the problem).

There are also some good rebuild articles on the VTR site :
(scroll down for links)
Not too difficult, but you'll probably want to make some of the tools required and buy a few others. Don't forget to use a new mainshaft circlip every time you install it ... I'd suggest buying a few spares in case you don't get it back together just right the first time.

Also be sure to check ALL the clearances ... don't assume that new parts fit correctly. In particular, there seem to be a lot of mainshaft gear bushings that don't fit properly ... on my last rebuild I wound up having to shorten a gear slightly and use a larger spacer washer because the new bushings were not long enough.

Personal preference : I don't like the narrow steel bushings that the TR6 used for the clutch cross-shaft to ride in. So I converted to the wide brass bushings from a TR3 (two of the RH bushing without the slot for the lock bolt) and added grease zerks for them.

Don't forget to add the taper pin reinforcement, and make sure the locating dowels are in place.

03-03-2008, 09:09 PM
Due to work commitments I have taken a break from overhauling a TR6 A-type OD box that I got off eBay. I didn't use any special tools to get it apart so far, even the circlip. The only disassembly left is the OD accumulator cylinder insert which I will need to make an expanding rubber puller for. The OD pistons were a fight but I eventually got them out with regular tools.

I hope to get back to it soon.

03-04-2008, 11:15 AM
Thanks for the info, from the looks of it I think I am going to rebuild my existing box.

My next question is has anyone removed the gear box from the interior without removing the engine? I have the tunnel off an it looks like it will come out without issue.

03-04-2008, 01:41 PM
My next question is has anyone removed the gear box from the interior without removing the engine? I have the tunnel off an it looks like it will come out without issue.

Yes, it comes right out.

Oops, I just jinxed you!

03-04-2008, 01:53 PM
Yes, it comes right out.

Oops, I just jinxed you! :iagree:

On both counts <<GRAEMLIN_URL>>/grin.gif

03-04-2008, 02:04 PM
I just remembered; don't you have to finagle it one way or the other because something hangs up on the floorboards? Clutch actuating arm or something?

Allow me to rephrase:

"It comes right out with a little finagling."

03-04-2008, 02:27 PM
Only 'finagling' I recall is that you have to jack the back of the engine up somewhat and support it that way, so the tail flange on the gearbox will clear the driveshaft tunnel. But maybe that only applies with the slightly longer 4-synchro (TR6) box.

There's a detailed procedure in the workshop manual.

03-04-2008, 04:25 PM
Due to work commitments

Ian: Remember, I'm a bit older and we have to have a serious talk about priorities. Work commitments indeed! :smile:

03-04-2008, 07:46 PM
Due to work commitments

Ian: Remember, I'm a bit older and we have to have a serious talk about priorities. Work commitments indeed! :smile:

Hangs head in shame and stands in the corner...

03-16-2008, 10:36 PM
Here is the latest update. I found a rebuilt TR4 gear box and it is installed and mounted up to the engine. So far I have had to make 3 modifications.

Rear transmission mount - The TR4 transmission is 1/2 inch longer so I had to drill two new holes in the cross member for the rubber mount 1/2 inch further towards the back of the car. Fortunately the bell housing flange was the same as the TR3 so longer bolts between the trans and engine were not required.

Cross Member - The cross member has a lip facing upwards towards the back of the car. When I moved the mount 1/2 inch to the rear this lip interfered with the mount. I fixed this by using a large hammer to bend the lip out to clear the mount.

Transmission Tunnel - The starter chamber in the bell housing of the TR4 is longer then the TR3. I have not done it yet but I think I am going to hammer out the tunnel to make space for the longer bell housing.

Modifications to rear mount:

TR4 Trans installed: