So I am sitting here waiting on some old timey 80-90 gear lube (w/GL-4 rating) and looking at the bottle of supplement.
This is going in our '67 4 speed with Saf-T-Track differential.
The bottle of LS additive says "recommended for manual transmissions". I've never heard of such.
Has anyone added this to their transmission? Any noticeable anything as a result?
BTW - I have pulled the tranny out to have a synchronizer replaced. Maybe this stuff would help? Although, it was about 45 years ago the last time I had a syncho replaced. I guess one every 50 years or so isn't too bad...
Cal

Yes, there is a GM synchromesh additive that is added to transmissions such as Muncies. The limited slip additive is a friction modifier and works to keep the cones or clutch plates in the diff from grabbing and chattering. If you go around a corner and your diff sounds like it's about to fall apart some additive may be all you need. Same goes for synchromesh transmissions, modifying the friction and allowing for smoother operation of the syncro cone/clutch. Some transmissions, such as the Tremec, just use synchromsh fluid and no 80/90. The fluid is quite thin compared to the 80/90 and can cause a lot of clacking in the transmission at idle with a large camshaft, which may cause alarm with an owner thinking his/her transmission is in a sad state. Been there/done that.
I think the limited slip additive and the synchro additive are close enough to be interchangable, such as stated on the bottle/can you have.

Thanks Al. I had seen the new synchomesh fluid, but you are right - it is very thin. I have just not heard of adding the LS supplement to the transmission before. I may give it a go, since the car will eventually be headed "back north" at some point.
Cal