ZF S5 17 Synchro Ring Question

I’m going through this transmission and it appears that it’s common to replace the synchro rings. Do the teeth of these typically wear or is it some other clearance? The teeth of the synchro rings I removed look very good, is there something else I should measure for wear.

BTW, I needed a die grinder to remove the large bearings from either end of the primary case; not much fun!
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Actually it's the inner diameter of the brass syncro ring that does the work. It acts like a brake on the gear surface that it mates with. This is why it's important to use the proper, old fashioned gear oil for this application; NOT the modern synthetics.

 

Thank you, Do you know what the tolerances are for this part?

 

No idea on tolerance. The ID of the brass ring actually "grabs" the mating surface of the steel gear, and acts as a brake. Any wear, or microscopic polishing can foul this up. It's probably not perceptable to the naked eye? This is why the gear lube is essential; it has to be the old fashioned oil. Sorry I don't have a good answer for you.

 

A little online research helps…the inside of the synchro ring has a slight taper which mates to a similar taper on the shaft, As the shifting fork pushes the synchro ring, the friction on this taper brings the ring and shaft to the same speed. As the inside of the synchro wears, the ring can move farther up the taper, until the synchro ring touches the gear on the shaft. At this point, the synchro ring can’t create friction ant the taper and needs replacement. On my transmission, this gap is pretty even for the rings at about .97mm. This appears to be about the standard clearance for synchro rings, so they look very good!
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