Has anyone else experienced this?
 

I recently could not get my T56 to go into gear. A friend suggested changing the gear oil, but I insisted the oil had only been in the transmission for less than a thousand miles and could not be the culprit.

I eventually changed the fluid and poof, the transmission worked properly again. I bought the transmission off craigslist and I know it had been sitting outside of the car for awhile....

Has anyone else had this problem? I'm curious to see if I'm driving on borrowed time and should be expecting to rebuild this transmission soon.

if the wrong fluid is in the transmission then yes this can happen. T56's are kinda pickey about clean fluid and the right fluid.

i'm running dexmerc, is there something else that is better? I just drove the car 40 miles and everything seemed fine.

DEX III is whats suposed to be in it. and depending on the year if you still have paper blocker rings you can't even run synthetic fluid in it.

so yes 40 miles with the wrong fluid sounds about right. change the fluid then drive it for a few miles and then change it again. aslong as nothing is messed up internally you should be ok.

The transmission is from a 96 and I believe it had a factory looking yellow sticker near the fill hole that said DEXMERC....maybe it said DEX III, I will crawl under there and double check.

should say DEX III. thats all GM used in all the manual transmissions i have ever worked on.