Ralph-
You ask about the trans popping out of 3rd gear...
When you decide to tear the trans apart, pay special attenion to 2 things.
1) The bearing and shaft nose at the 1 to 3rd motion shaft connection. (1
motion shaft is the one the clutch plate slides on, also called input shaft.
3rd motion shaft is the big long one that the output flange is bolted to).
Since 3rd gear is at the very far end of the 3rd motion shaft, any play which
develops at the 1to 3rd bearing, will be exaggerated. If play develops here,
the 3rd motion shaft will deviate from straight, forming an angle between the
two shafts. Because of the angle formed, the gear teeth will tend to push the
syncro hub back toward neutral. Closely check the bearing for play/wear and
the nose of the shaft itself for wear. The bearing can be replaced and the
shaft sprayed up and turned, if need be.
2) The 3rd to 4th syncro hub itself can wear. (The hub consists of an outer
ring which the syncros fit into, and the shift fork rides in. and is splined
to an inner piece. Wear can develop between these two pieces, resulting in
slop between them. This can also allow an angle to exist between the two
pieces which again will tend to push the hub back toward a neutral position.
The syncro hub also has springs and detent balls inside of it to help hold
the hub in position when in engaged in a gear. The springs can tend to lose
some of their tension over the years and allow the hub to "pop" out of gear
also. However, don't get your hopes up on this cause as it is most rare, and
usually the hub will be worn by this time anyway.
You do not mention any gear "noise" so I will assume the lay gear shaft is
not the culprit here, but when you take it apart, check this shaft first as
it can display your symptoms, but is usually "noisey" also.
Gotten the Shaft on this myself...
Nick in Nor Cal
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