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Installing O/D A-type Transmission from TR4 or TR3 into 1972 TR6

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mbudman Mark Budman
Montreal, Quebec, Canada   CAN
I have a 1972 Triumph TR6 and I traded for an overdrive transmission (A-type). I had a broken A-type in my car previously, so when my clutch needed replacing I thought I could swap it out and put in the new one.

The person who gave me the working A-Type Overdrive transmission said it came from a Triumph TR4. However, when I put the transmission on the car, the bolts do not line up. Only one of the 12 bolts line up.

There are only two switches on the new transmission, which after discussing with someone, it seems that the transmission might have come from a TR3 and not TR4 as my original A-type transmission (that was in the TR6) has 3 switches for overdrive.

Does what I am writing make sense?

Would you have the appropriate adapter kit?Is there an adapter kit available? Does anyone know where I could purchase one?

Thanks in advance.

Mark

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mgruber921 Avatar
mgruber921 Marvin Gruber
Florence, Alabama, USA   USA
I have put TR6 o/d trans in TR3 and TR4's before with very little effort. Bolts line up fine. SO it should go the other way with no problems as well. You must not have gotten a TR6 trans but one maybe out of a Stag or sedan. Two sws mean o/d on 3 and 4th gear only. 3 sws o/d on 2,3 and 4th. If its a correct TR6 trans you can swap the top shifter cover and have 2,3 and 4 th o/d.

Marv

mbudman Mark Budman
Montreal, Quebec, Canada   CAN
The problem is not the OD transmission itself. The problem is lining up the transmission with the engine.

The bolts do not line up - the bell housing and the bolts to the back of the engine do not match.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
I agree with Marv about the bolt holes. There is one hole that might be different (doesn't get used when installing a TR6 box in a TR3) but if you are seeing a bunch of them, you must have something else.

But it only takes 2 switches to get OD on 2,3,4; as one switch works in both 3rd & 4th. The third switch is for backup lights.

It's a shame you traded away your old gearbox; as it's not too hard to replace the overdrive on a box that is already equipped for it. You could have moved the OD from the mystery box to the one with the broken OD.

Stag also uses the same bolt pattern as TR6. They won't interchange because the Stag has a longer input shaft, but the housings will bolt up.

Lots of other period cars used the A-type, though. I've got a mystery gearbox with A-type myself (bought just to get the OD for parts).



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

mbudman Mark Budman
Montreal, Quebec, Canada   CAN
Actually, I still have the original gearbox. It was being used as 4 speed only because overdrive did not work. I did take a look at it, but almost all the inside parts are worn. It is in very bad shape.

I traded a TR6 engine for the gear box.

Do you think there is an adapter kit that can solve the problem?

Thanks,

Mark

philstr6 phil Jaegeling
arroyo grande calif, USA   USA
How about a picture of the gearbox
Phil

Triumph Racer Avatar
Triumph Racer Patrick N
south bend, IN., USA   USA
1962 Triumph TR4 "My First Triumph"
1962 Triumph TR4 "Big Red"
1964 Triumph TR4 "Ugly Duckling"
1971 Triumph Spitfire MkIV    & more
Yes you will need to post some pics even for us to try to figure it out for you. I assume they look identical to you on the outside? Otherwise God knows what you have,it may be from an Alpine. I can tell you from experience when I put a overdrive in my old TR4 race car the box was a newer J-type from England. It came from a Triumph 2.5 PI. It fit as others have mentioned with only the locating dowel now being in a bolt hole.



Sometimes you succeed,other times you learn.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Very few adapter kits available; I've never heard of one to put another period transmission in. There's the HVDA Toyota conversion, of course; and I think there was someone making a conversion for a Ford (?) box; but they are both for much later transmissions.

Oh, BTW, the TR2-3 gearbox even looks different on the outside. The left side has a raised flat area, while the TR4-6 version is curved and has a distinct cylindrical bulge lower down. This is a TR3 version:





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

Triumph Racer Avatar
Triumph Racer Patrick N
south bend, IN., USA   USA
1962 Triumph TR4 "My First Triumph"
1962 Triumph TR4 "Big Red"
1964 Triumph TR4 "Ugly Duckling"
1971 Triumph Spitfire MkIV    & more
Randall,I think you are getting a bit too technical now. His problem is obviously the bolt pattern. We don't need to get into all the intricacies inside and outside the box.
That only shows how much we know and how much Mark does not know and confuses him. BTW did you forget to mention the TR2-3 gearbox is also a top fill/check trans?



Sometimes you succeed,other times you learn.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1221153 by Triumph Racer BTW did you forget to mention the TR2-3 gearbox is also a top fill/check trans?
No, didn't want to confuse the issue too much. Besides, many of them aren't. The top fill (and dipstick) was deleted at TS50001.



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

mbudman Mark Budman
Montreal, Quebec, Canada   CAN
Hello,

I have the serial numbers for my transmissions:

New trams: 22/61712/903696
Old trams 22/61753/614522 (A-type)

Car is a 1971 Triumph TR6

Thanks for all your help.

Cheers,

Mark


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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1221211 by mbudman Hello,

I have the serial numbers for my transmissions:

New trams: 22/61712/903696
That's the overdrive, not the transmission. But the 61712 should indicate it was originally for a later TR4 or solid axle TR4A, with the big accumulator piston and rubber O-rings on the operating pistons. Sure looks like the right gearbox in your photo, too.

Any chance of a photo showing the bolts not lining up?



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

philstr6 phil Jaegeling
arroyo grande calif, USA   USA
Mark
22/1712 is for tr4-tr4a up to oct 64
22/1753 is tr4a-tr6 up to march 71

you have the correct overdrives,one question ,does the input shaft flush with the case or does it stick out beyond the case,and if it sticks out beyond the case that trannie will not fit till you fix the input shaft to the same as 1753 one,take a look at that,easy fix if it sticks out,and then the trannie will go all the way in,not sue if that will help your bolt holes,but could that be the problem

Phil

johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
If the input shaft needs to be replaced with a shorter one, wouldn't he also have to change out the front bearing retainer and throw bearing assembly?

philstr6 phil Jaegeling
arroyo grande calif, USA   USA
John
if this trannie is tr4,the input shaft noise is longer,dont have to replace the input shaft,A dremal tool and trim the input to size,you can get the measurement off the old trannie,you only have to trim a 1/4 in or so off the input shaft
phil

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