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General Tech Different style synchros which is better

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Got_All_4

Got_All_4

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"Planning" on or starting to put together the tranny today. You know how that goes though! Anyway been looking at the difference in the synchros. The one that came out of my A type tranny is the smooth one in the pic. The other is an original that came out of the TR4 tranny and my J type had that design too. When I rebuilt the J type last year and purchased new ones they were like that too. So which is better? I think the ones with the channels were designed to get more oil into them. However centrifugal force you would think would throw the oil out through the channels. The smooth ones would hold the oil in but the synchro is suppose to grab the taper on the gear and the oil would make them want to slip. Can or should I cut or file a channel in the smooth ones or leave well enough alone?
 

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A question...what was the source of the new synchros, that had the channel, that you bought to rebuild your J type?
Regards,
Bob
 
Either style will work just fine. Lightly press the synchros onto the gear cones and then try to twist it. It should lock hard and not turn at all if the fit is correct. You may even have to pry the ring back off when the fit is perfect. If you press them together and can still twist the synchro...it's dirty, worn or warped. Even a brand new ring can come warped. I learned that many years ago when I rebuilt an old Muncy 3 times, and each time a different gear would grind. I finally talked to an old head who explained the GM rings were garbage. He sold me decent rings and showed me how hard they should lock on the cone. I've never had a weak gear since.

So, either design...just make sure they fit like they should, and use the one that fits tightest. Even if it means mixing the types on the re-build.

Edit...the grooves were an old racing trick that apparently made it into production. We used to file the grooves to prevent hydrolock when speed shifting. The grooves allow the oil to get out of the way so the ring contacts the steel cone quicker...or at least that was the idea. Another trick we used, that hasn't made it into production, was to grind off every other sprag tooth on the rings to quicken the shifts too. My speed shifting days are over, and neither mod is needed on a street rebuild.
 
Synchro rings are one of the tranny rebuild parts where it's worth making sure you have the best quality item. There were several batches of poor ones from some of the well known suppliers and it's a false economy not to get the good stuff.

Dan
 
Source was from Moss. Local distributor. He assured me that the poor quality ones were from many years ago and are out of the parts system by now. I 'm reusing the old ones in this rebuild and they look fine and grab very well. I read many an article that if the old ones are fine it's best to reuse them vs new ones. Just got done cleaning and polishing everything. Looks like Monday is a better day to assemble. Forgot about the Super Bowl party at my sisters an hour away. Guess I'll take the TR7.
 
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