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5th and 6th gear vibration
Some transmissions have a clearance between the mainshaft journal @ 6th gear and the 5/6 driven gear. This allows some movement, and then wear of the splines- and exhibits itself through no-load vibrations in 5/6th gear. Very annyoing on the freeway.
There is a transmission shop in Texas that will weld up the main shaft and regrind it so the gear is press-fit, as called out in the manual, instead of slip-fit.
Here is a video showing where the wear problem is.
Reverse pop-out
Early generation CTSV's had problems with reverse popping out of gear. There were multiple modifications to the transmission to change this problem. The descriptions here are in order of the pictures in the album, but do not directly align 1:1 with picture or subject of pictures.
Front plate and extension housing on old unit is directly cut for shift rail. Newer case has bushings inserted.
Shift rail on old unit has cutouts at the ends where it slides within the case, allowing more slop and perhaps causing more wear on the case . Newer shift rail is all the same diameter at the ends.
Old Reverse shift fork is blockier, square-cut, and more likely to come in contact with neighboring shift fork if there is slop in the shift rail (due to case wear @ shift rail)
Older unit front plate is mostly flat, newer front plate is cast with a small difference in thickness... not sure why (oil pooling in it in picture, with 3944 sharpied on it)
Old 1/2 shift fork stops the reverse shift rail much earlier in throw due to blockiness, newer shift fork is more rounded and has additional clearancing to allow more reverse shift rail movement
Old Shift patter plate is about 1mm shorter in full stroke front to rear than new one
Case mid-support has hole in it for shift rail. On old unit, oblong hole with lots of clearance around rail. On newer cases, hole is round and shift rail barely fits through it.
Newer Front plate has a catch-hook by the mainshaft bearing to grab oil from gear sling and provide it to the bearing. Old front plate does not have this hook.
Couple more pictures of shift rail bushing (and lack thereof) in front plate. Same condition exists for tailhousing.
Old mainshaft 1/2 synchro is held on with c clip. New mainshaft, 1/2 synchro is held on with split ring + ball bearing + solid ring. Mainshafts cut differently to allow for this (second from right set of splines) Split ring and ball bearing seen on workbench in picture, and closer in next couple of pictures
Last picture shows spline wear.
See pictures in album here:
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