---- Jim Henningsen <trguy75@gmail.com> wrote:
> List:
> I have a jtype od transmission that was rebuilt about 8 years ago. Started
> having third gear grinding issues on hard acceleration and deceleration (auto
> cross and spirited driving) so had new German made brass synchros installed
> about 2 years ago. Got rid of Taiwanese synchros installed during original
> rebuild as we thought that was the issue. The new German synchros didn't solve
> the problem.
My first thought would be the clutch or pilot bearing dragging. Do you have
the proper "dowel bolts" to precisely locate the gearbox to the engine plate?
How are the thrust washers? How far off the floor does the clutch start to
engage?
Next I'd be looking at things like the detent force in the shift hubs, excess
play in the thrust washers/bushings, and wear on the gears. There's a lot more
to shifting than just synchro rings; and not everyone checks those things when
doing a rebuild. Note that even new bushings are frequently too short and/or
the wrong diameter. Last time I did a gearbox, I bought two of each and still
wound up having to reuse the old ones. Had to have Herman make some spacers,
too.
How much clearance was there between the face of the new synchro rings and the
dog teeth, with the synchro seated on the cone? IIRC it should be at least
.050".
Last, although not too likely I think, be sure your shift rings match your dog
teeth. There was a subtle change in production, and mixing parts can cause
problems. I know someone who spent years trying to figure out why a freshly
rebuilt box would jump out of gear, and that was eventually discovered to be
the problem.
http://goo.gl/FjDq3
Randall
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