Triumph Repair: 72 TR6 Transmission, manual transmissions, gear lever

Question
My TR6 will sometimes slip out of third gear if I am using the engine to decelerate. Is this a sign of a significant issue with my transmission or is there something that can be adjusted to address this?

Answer
It may be a sign that the 3rd gear synchro is starting to wear out.  If it starts popping out of the 3rd gear while driving (not decelerating), then it is almost for certain.

You dont' have to replace it; you can just hold it in 3rd while in 3rd gear.
Adjusting the gear shift may help; you may not be fully engaging 3rd gear; but there isn't much to adjust; just make sure that the gear lever is fully seated, the bushing(s) are not worn.

You shouldn't need to use the engine to decelerate these days; that is a hold over from when brakes on cars were not as strong (drums all 4 wheels).  Yes, it feels good, but may be one reason the syncros are wearing.

Replacing a syncro isn't difficult for someone who has rebuilt manual transmissions before, but it won't be cheap; you may be better off finding a used TR6 transmission and just swapping out once your gives up the ghost.  Unless, of course, yours is an OD, and then it won't be easy to find one used; they are like gold.