OP didn't say what kind of transmission.
If it's a manual trans, in SOME cases I'd say "maybe it would be OK" but both the manuals used in the majority of GMT400's have fairly specific lube requirements. The light duty 5 speed (NV3500 and its variants) want Syncromesh, and the heavy duty 5 speed NV4500 wants Castrol Syntorq LT (known as GM's "Synthetic Transmission Lubricant") or you're asking for trouble. Now if it's an SM465 4-speed you could probably dump a portapotty in there and it would live...
For any automatic transmission or a transfer case that takes ATF? No way in hell. For starters, it's too thick (much higher viscosity than ATF) and isn't going to be anywhere near the right product in any way whatsoever.
So to repeat what the others said, no, but with a little elaboration.
Richard