A transmission that does not want to stay in gear usually has one or two
problems.
1) The first is that the shift fork has gotten so worn that it will not fully
push the selector fully over the gear dog teeth, and will not allow the detente
ball to fully engage the recesses. Also, as someone mentioned, the springs
behind the detente balls may be weak. Not a very common problem, though. This
condition, if you read the manuals, is easy to detect before you ever assemble
the trans. There is a very specific amount of force that is to be applied to
each selector ring (gear) before it pops loose. If it is wrong, the trans will
be either very hard to shift into gear, or will just slide in and out, often
overriding the synchros, since insufficient pressure is applied to stop the
gears from spinning.
2) The second is that the dog teeth on the gear, as well as the teeth in the
associated selector ring have become worn, usually with a very slight bevel.
This bevel is like a very, very small wedge in cross section. The result is
that with the slightest pressure, the two mating bevels cause the gear and
selector ring to simply push apart. This can generally be seen by simply
pulling the top of the trans case off, and observing the dog teeth on the gear,
in your case, third. This problem generally has its roots in someone's driving
style, especially those who like to think they are at Sebring, and are
power-shifting everywhere. They snatch the trans out of gear without the
clutch being fully disengaged.
To cure either/both problems requires the trans be pulled, and rebuilt.
Cheers.
dncullig@us.ibm.com wrote:
> Fellow LisTRs -
> Once again, I come looking for help. The J-type OD that I had
> installed in my
> 76 TR6 this past May is acting up. It popped out of 3rd gear once or twice
> 2 weeks
> ago and I didn't think much of it. Now, however, it simply will not stay
> in 3rd gear.
> It pops out regularly, even when under power. It'll stay in 3rd if you
> hold it in, but even
> then you can feel it trying to pop out. None of the other gears seem to be
> similarly
> affected. I'm going to take the tranny out of the car and am planning to
> take it back
> to the guy who re-built it back in February, but would like to tap the
> collective wis-
> dom of the list first to see what might be wrong. Any ideas and/or best
> guesses
> are welcome. I'd hate to have to go back to my non-O/D transmission,
> especially
> with a rather long trip to the VTR Regionals coming up in a few weeks, but
> I need
> the car to be reliable. Thanks for any and all input.
>
> Dennis Culligan / 1976 TR6 CF57948U(O) - TR6IUMPH / Highland ,NY/
> DNCULLIG@US.IBM.COM
> See www.britsofthehudson.org for info about our club
|