depending on the condition of your tranny i would go with honda mtf/atf. the gm sychromesh i have heard that it is a bit too thin for straight use, and some choose to mix it with honda mtf to prevent it form messing up their trannies. personally i just use honda/acura oem mtf fluid and have had no problems, grinding or otherwise. and this was on a 10+ year old transmission. hope that helps.

by the way, anyone know if the honda and acura mtf is the same with a different bottle, i have always had it done and so havent personally compared the bottles. just curious.