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The failure in my 94 Aero's 5-speed turned out to be a broken snap ring in front of the 3 - 4 synchro hub on the input shaft. Eriksson says it's a "known failure item". Not only that, they say that Saab did an upgrade, modifying the hub to accept an added thrust washer between the hub and snap ring. The shaft also needs a slight mod (remove enough of the splines to accomodate the thrust washer), which Eriksson did for $50. They also installed some "leaf springs" in the synchro (anti rattle, they said). I didn't get to see any of this stuff because I sent them all the input shaft stuff and let them assemble it and press on the new bearings. Unfortunately, they do not know when Saab started the upgrade. That would be really nice to know, wouldn't it, 95 owners? Anyone got any contacts at Saab who could tell us?
As a caveat, I found two things misassembled on the output shaft: 1) The synchro sleeve for 1 - 2 appears to have been installed upside down, with the groove for the shift fork facing the wrong way. 2) The "beans" for the 1 - 2 synchro were installed in the wide slots in the hub rather than the narrow slots, where they should be. How it could work with these anomalies is beyond me, but that's what I found. Needless to say, that could explain my snap ring problems, even though these goofy misassemblies were not on the input shaft where the snap ring was.
As for the weird symptoms - self-destructive banging/binding in reverse and occasional clunks when in neutral with the clutch engaged, but otherwise perfect operation in all forward gears, at all speeds, under all loads - apparently, the gears thrust-loaded toward the back of the shaft, in their normal positions, when in forward gears. Reverse forced them forward, and there was no snap ring to retain them, so 4th gear tried to engage while reverse was engaged. In neutral, the gears would shift forward and 4th would try to engage lightly while the clutch was engaged. That's my theory anyway. There were some exceptions - once or twice it made binding noises in low at parking lot speed after having bound up in reverse. That probably was before the gears could load backwards sufficiently. Symptoms appeared to have been related to turning, but I think that had more to do with parking lot speeds and backing out of parking spaces than anything else.
The transmission is still completely disassembled. I'll start trying to reassmble it this weekend. Setting up the differential is not trivial (special tool required), so I won't be replacing the differential or output shaft bearings. My local Saab dealer mechanic told me to put the old crush sleeve (sets output shaft bearing preload) back in and under no circumstances try to crush in a new one, because it's the job from hell. I'm going to try it anyway, because my mechanical engineering guru says to do it. Another special tool is required, but I think I can fake it. Wish me luck. Sorry for the length of this post. Quasimotors.com will be updated with the experience before too long. I am also trying to struggle through the last steps of wrenching the domain away from them that has it now so I can go to a new service provider (no more "out of bandwidth" foolishness).
posted by 206.72.252...
, Fri, 14 Feb 2003 07:44:20
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