Originally Posted by supershaft
The leeway in shimming is huge. The leeway in getting pre or post pressure face angle change helical gears is zero. I would read up on the helical gear pressure face angel change disston mentioned and make sure that you not only got the right one but that the other two already in there are the earlier PFA gears. To confuse the matter I swear I have seen newer late PFA gears without a X on them anywhere. You can barely see the difference IF you look closely. PFA is NOT the helical angle. They never changed that. PFA is about the shape of each individual tooth. I have seen the PFA's mismatched many times and they work just fine for a while. A couple of thousand miles is usually enough for mismatched gearsets to eat themsleves. They do make more whurring noise while doing it.
I guess I don't quite grasp what your point is--I'm not trying to be a smart ass or snarky here. I'm not singling you out, but there does seem to be a trend towards making this all a bit more complicated than it needs to be.
I know that 74/75 were years of change in the gearboxes--and that parts from a 75 probably might be problematic in my 76 five speed.
If, as Disston says, 82/83 was a change year for the helical gears, I should be golden for helicals if both my replacement shaft and the offending shaft are from the same displacement and model year, no? At the very least as the offending gears are the 1 & 2 gears on the shaft (last ones before it outputs to the flange) I may be able to just pull those bad gears off and put the good ones in?