Originally Posted by rockandroller1991
I have a 1980 camaro Saginaw 4-speed and recently the 1st and 2nd went out and it wouldnt shift between the 2. I poped the the side shaft off and the cluster gear looks great and all the syncro's look good. but the first and second gear wont slide on the cluster gear. does anyone have any idea of what it might be?
To start with this is a constant mesh transmission, which means the output gears are always engaged with their input counterparts on the cluster gear. Gear selection happens thru the synchro collar which when pushed by the shift yoke that rides on the collar, it will engage the synchro's blocker ring first with three dogs that press the blocker ring into a mating surface on the desired gear. When that gear and the speed of the output shaft match, the collar will slip over sets of external teeth on the blocker ring and the gear locking both the gear and synchro to the output shaft thru the collar.
A failure of the yoke to move the collar would indicate a failure or miss alignment of the linkage external to the Saginaw. If the side cover is removed, so the shift linkage is disconnected and the shift yoke still won't move then there is a problem with the yoke's internal linkage or it's bent. There is a detent in the side cover that can become damaged and hang up the yoke's hardware.
A failure of the collar to be moved when the yoke is not in contact would indicate a failure of a component inside/under the collar. There are serrations where the collar moves upon and is locked to the output shaft, they are matched within the collar, if damaged they can hang the collar up. There are three dogs that are evenly spaced around the shaft spline adapter under the collar, within, are two spring steel circular torsion springs that press the dogs outward against the collar. There is a groove inside the collar that catches the dogs and moves them toward three large reliefs in the blocker ring. If any of these parts are excessively worn, broken, or have come out of position; the collar will be jammed and become immovable.
To see what's under the collars the tail-shaft ( also called main-shaft or output-shaft) has to be removed, so it can be disassembled.
There is a needle bearing inside the input gear that the main-shaft engages. If these have failed the shaft will become misaligned and moving the synchro collars will become difficult if not impossible. There are similar bearings within the cluster gear that can have the same effect. The input shaft/gear rides on a ball bearing in the front of the case, a failure here will jam shifting up and take out the needle bearing the output shaft rides on. There are numerous thrust bearings that if failed will allow the cluster gear and or mainshaft to slip fore and aft during shifts which can let the innards of the syncho assembly all out of position. There is a bushing on the end of the output shaft inside the tail housing as well as another ball bearing forward of that on the mainshaft, failures here will present similar results from engaged gears randomly popping out after being selected or jamming the shift collars by allowing their internal guts to get out of position.