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Any issues putting a TR4 OD gearbox in a 60 TR3a?

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brucejon Avatar
brucejon Gold Member Bruce Jones
Santa Cruz, CA, USA   USA
1960 Triumph TR3A
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
I understand it just bolts in Is this the case?



60 TR3A (red), 62 TR3B project, 72 TR6, 69 Mk3 Spitfire EU setup
https://spitfiremk3.wordpress.com

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RJCox Avatar
RJCox Ronald Cox
Fredericksburg, VA, USA   USA
Bruce, I'm not an expert, but I believe my Dad's 61 has a tr4 OD tranny in it. He also has a tr4 non OD tranny that he says should bolt right onto my 60 powerplant.

Differences I see off the top, speedometer cable needs to be longer, shifter arm on the 4 is bent vs straight on a 3, and if course the switch. I think the shifter can be swapped and the speedometer cable is readily available.

Others more well versed will chime in I'm sure.

I've really thought about finding a 4OD tranny before I'm done and doing the swap. They're not cheap or just laying around, so stock it is for me for awhile.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Pretty close. The 4 synchro box is just a bit longer than the 3 synchro, so you should modify the frame crossmember to let the rear mount sit farther back. Sorry I don't have a good photo


In my case, I also had to bend the lip on the back of the crossmember back just a bit, so it didn't hit the gearbox. That may or may not be an issue for you.



Also pay attention to where the speedo cable goes through the opening on the side of the trans tunnel. I had to grind away just a bit of the sheet metal but again YMMV.

It seemed like the speedo cable was getting damaged from rubbing on the edge of the floor too, so I added a length of split fuel line as protection.

I believe the TR3 lever will fit in the TR4 top cover without modification. The TR4 lever will work OK, but ISTR that was the one where I had to be careful how I gripped the knob when shifting into 3rd. IIRC it came close enough to the ignition switch to pinch a finger between knob and key. But that was a long time ago (1975?) and YMMV.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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brucejon Avatar
brucejon Gold Member Bruce Jones
Santa Cruz, CA, USA   USA
1960 Triumph TR3A
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
Thanks both of you.

Randall, modify crossmember how? Drill new holes? I installed a J type in my spitfire, had to mount a different cross member in it, so I get the general idea



60 TR3A (red), 62 TR3B project, 72 TR6, 69 Mk3 Spitfire EU setup
https://spitfiremk3.wordpress.com

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
What I did was to drill new holes almost touching the old ones, then file out the web between them to form a slot. Leave the nuts loose until the engine and gearbox are in place and the mount bolted to the gearbox, then finish tightening the nuts.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

brucejon Avatar
brucejon Gold Member Bruce Jones
Santa Cruz, CA, USA   USA
1960 Triumph TR3A
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
Sounds straight forward, thx!



60 TR3A (red), 62 TR3B project, 72 TR6, 69 Mk3 Spitfire EU setup
https://spitfiremk3.wordpress.com

RJCox Avatar
RJCox Ronald Cox
Fredericksburg, VA, USA   USA
My 3 tranny has a straight shift lever, but the 4's shift lever bends halfway up towards the rear.

Now, that could be the way it came from the factory, or gotten bent by someone to modufy it, or even damaged, but I don't think it's the last two. I planned on swapping out my shift lever either way since my 3 syncro's shift lever looks brand new (I think the PO did a bunch of work on the drivetrain).

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
TR4 shift lever definitely curved from the factory. It also isn't hollow (the TR3 lever is), and takes a different knob. The threads for the knob are coarse pitch and smaller; while the TR3 threads are 7/16" and finer even than UNEF. (UNEF is 28 tpi, while the shift lever is 32 tpi IIRC).

They changed it again for the 4A, but the knob threads stayed the same.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

mgruber921 Avatar
mgruber921 Marvin Gruber
Florence, AL, USA   USA
Shift levers swap out with no mods. You can use a 90 degree angle gear box on the speedo cable but they are bad to break cables so Randalls way works fine
Marv

RJCox Avatar
RJCox Ronald Cox
Fredericksburg, VA, USA   USA
Thise aftermarket walnut knobs usually have a nylon insert that "threads" onto the shift lever regardless.

My 3 tranny has a tr4 knob on it (came that way) and the exact knob (aftermarket) is on our 4 tranny as well, though it is showing its age.


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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Some do, but not all. I didn't like the knob with the plastic insert, as it would sometimes slip under 'spirited' driving. So somewhere in my parts bins, I have a knob that looks very much like the first one above (except for almost all of the original finish being worn off), that has 7/16-32 metal threads. It turned out to not be a whole lot better, though, I had to glue the metal insert back into the wood several times.

Like Marv said, the angle drives are fragile (and expensive). IMO the long cable (as original) is a better choice.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

RJCox Avatar
RJCox Ronald Cox
Fredericksburg, VA, USA   USA
I agree.

I like the walnut knob, but I remember my dad having a chromed ball at one time. It was just the right size. Granted, in cold weather it would be awful to have your hand on it fir very long.

I'm torn between keeping what I have vs. swapping just to go from a 3 syncro to a 4. It would be easier to decide if my extra had an OD.

DonP Avatar
DonP Don P
Frankfort, IL, USA   USA
Just bolted a TR4 Trans with OD to my TR3B (TCF) last month.

It was less than 3/8 inch longer and a little die grinder work on the bolt holes, as indicated in this thread solved the problem.

Straight bolt in.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1595572 by RJCox I'm torn between keeping what I have vs. swapping just to go from a 3 syncro to a 4. It would be easier to decide if my extra had an OD.

FWIW, I've driven all 4 combinations. If it is no extra work (meaning the gearbox is already out and you can put either one back), I'd definitely go for the 4 synchro. But I sure would not go through all the work of R&R the gearbox just to gain synchro on 1st. It's nice, certainly, but not all that nice. Honestly, even after all these years having it, I still don't use it much. A good running TR3 engine just has so much torque that it will walk away smoothly from just barely moving, in 2nd gear. I used to routinely do "Hollywood stops" at stop signs without ever shifting to 1st. And I long ago gave up trying to keep up with the Miatas (let alone all the muscle cars running around).

IMHO, YMMV, NFI, etc

OD is a different matter. IMO it's definitely worth doing the R&R to gain OD. (In fact, my current OD came from a TR4 that I mostly bought just to get the OD. I saved a few other things, but most of it went to the scrap yard.)



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

brucejon Avatar
brucejon Gold Member Bruce Jones
Santa Cruz, CA, USA   USA
1960 Triumph TR3A
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
This one has OD, and I love it in my spitfire. Probably the only thing I will "improve" on an otherwise pretty original car.



60 TR3A (red), 62 TR3B project, 72 TR6, 69 Mk3 Spitfire EU setup
https://spitfiremk3.wordpress.com

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