The WC T5 must use ATF. A Stovebolt member was kind enough to reference his S10 Owner’s Manual and it said ATF for his NWC T5.
You will NEVER go wrong with DEX/MERC ATF, no matter what T5 you have, NWC or WC. The ATF called for in the 88-92 Camaro T5 was DEXRON II which is no longer available. Other DEXRON ATF choices are too thin. I’m friends with the owner/operator of a reputable T5 transmission shop in Atlanta and he said to use DEX/MERC ATF. I’ve used synchromesh in a NWC T5 but switched to DEX/MERC. I like it better. I’ve had people tell me their T5 wouldn’t shift properly with gear oil.
When GM made the leap from dexron III to dexron VI it superceded all prior versions in automatic transmissions. Manual transmissions & shift on the fly transfer cases kept Dex III now relabeled as Manual Transmissions & Transferred Case fluid.
I would say that's what the Dex / Mercon is.
Dex VI is too slick for the synchronizer to function properly.
It is a huge leap forward in older GM automatic transmissions!
