Hello.

Automatic Tranny Fluid is not good for a Manual Tranny.

Get some Manual Tranny at the Dealer or at a GM Dealer; They sell GM Synchromesh, might have changed the name for Delco Synchromesh. It should be a GL4 if I remember right.

Other option would be to get some Redline Manual Tranny Fluid. Some have use MT90 or the MTL while some have put a mix of MT90 and MTL with good results. Redline Tranny Fluid is also Red as Automatic Tranny Fluid. Having a Red Fluid in the Tranny helps in pinpointing a leak between the Engine and Tranny. Having said that, most Manual Tranny Fluid should be somewhat the same colour as Engine Oil.

Lots of option out there, whatever you do change it for a Manual Tranny Fluid.

Hope this helps.

Ghislain.