Crunchy 3rd gear in 4 Speed manual

[cbenz1]

When upshifting into 3rd gear on my 71 280SL, it occasionally crunches, but still goes in.  I assume it is a synchro.  Anyone have a NJ based repair shop that has experience with repairing this 4 speed.

Thanks

[Benz Dr.]

There can be several different problems relating to gear clash. Syncro wear is one of them but there can also be too much end play on the main shaft. I've seen where the slotted nut came loose and caused all sorts of trouble but I've found that most of the time there aren't enough shims behind the input shaft bearing. This shaft is supposed to have zero end play but often has .030'' - .045'' which is then taken up by the syncro as it moves. The syncro is supposed to grab making the teeth line up on both the snycro and gear but the extra play prevents this from happening.