1st gear grinding

I own a 91 s-10 and i replaced the gear oil in the 5-speed gear box with valvoline 80-90 weight gear oil. When I first accelerate from 1st gear there is a grinding noise from the transmission. This only happened after I changed the gear oil. I contacted the gm dealership and they told me that some 91's took transmission fluid and some took gear oil. When I drained the transmission the fluid was red, in which my thoughts where that is was transmission fluid., but the service manager told me that gm's gear oil is red. So the only way I determined that it may still be gear oil is by the smell, because you usually can definately tell by the way it stinks. Am I crazy or can someone tell me if there is anything else that could be wrong beside pulling out the tranny to look at first gear. thanks for the help. Oh, also it does not always grind when taking off from 1st gear, just off and on.

I did the same thing with my '94 I moved and took the gearshaft out for towing..I replaced it with the oil it said to, but, it grinded BAD too.
try the other oil, it will be OK

thanks for the info :screwy:

Go and find out the exact fluid your truck takes.

And I wouldn't keep driving it with the gear oil in it.

Chances are you might be causing damage.

to my knowledge all s-10s took dexron mercon atf, and did u check your trasfer case fluid level, cuz they share oil, and if you emptied the tranny, you probably emptied the transfer case too, and didnt fill the whole thign back up all the way

He has a manual.