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Triumph TR6 - Engine Out

Hi Guys:
Finally, after years of unavoidable delays and pure procrastination on my part I got the engine and gearbox out of the TR6 this afternoon. The new engine and gearbox are pretty much ready but the messy part is going to be the detailing and painting of the engine bay and to finish cleaning and detailing the front part of the frame. Including a pic.
I have a question: a few years ago I bought what I thought was a TR6 gearbox and after cleaning/degreasing it I found the Comm # to be CT78323, which I'm told is for a late TR4A. The boxes are virtually identical. The reconditioning parts I bought for the existing TR6 gearbox all fit perfectly, including the throwout and carrier bearings. Anybody know if this is a TR4A box and if there would be any gear ratio issues with fitting it to a TR6? I'm fairly comfortable with the swap but a buddy advises caution. The seller took it out of a TR6 he scrapped and there is no possibility of returning it to him. I also posted this on aother forum looking for input from TR4 drivers. Advice greatly appreciated.
Cheers and a Happy New Year to All,
Bob
1976 TR6

Bob Evans

Hi Bob

I can't offer any knowledge about the difference in gear ratios but I would guess that if it came out of a TR6 then you may be OK.

You may want to confirm that the CT number is indeed a TR4 - I don't know the full range of TR6 commission numbers. My TR6 has a "CD" transmission commission number

I would guess the TR4 has a little higher ratio in first, second and third to make up for the smaller engine but 4th gear should be the same 1-1 ratio. So it should be a little faster off the start but you will have to shift earlier.

Good luck with it.

Regards, Mike
Michael Petryschuk

Thanks Mike. I was beginning to despair of getting any help on this as the other forum is pretty quiet too. So far I have only that info on gear ratios, which I can live with. The input shaft is longer on the TR4 box but it's been suggested it can be cut if it won't mate with the flywheel. I'll try mating it to the old engine on the floor. If the bell housing snugs up I'm okay; otherwise I will cut the shaft. If any body else has any info I'd be glad to hear from you.
Thanks,
Bob
Bob Evans

Call Quantum. They will know
Don Kelly

Hi Bob

Reading the chapter on gearboxes in How to restore Triumph TR5/250 & TR6 4 cylinder 4 synchro boxes were prefixed CT, LE, LF, MD, ME, MG, MK, VA, and VF. If this came out of a TR6 I would hazard a guess that someone has built the box to suit a TR6 using a TR4 case.

Colin
C J Norcott

Colin:
I'm told by my guy in BC the box has a TR6 top cover but it definitely has the TR4A input shaft, which is longer. The crank is cut deep enough to accept the longer shaft so that problem is licked. If the gearing is different, worst case is a little more low-end torque and speedo error. I'm also told the speedo can be recalibrated if necessary. Since I am looking for a J-type OD down the road I may just find the error and compensate for now. The box is nice and much better than my TR6 box so I'm happy for now and currently sanding in the engine bay so lots of dirty stuff to do.
Cheers,
Bob
Bob Evans

This thread was discussed between 30/12/2011 and 08/01/2012

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