I have a 1992 chev. p/u I may have run it low on trans fluid.?

Question

Its been slipping for about 20 mi.
I pulled over and put a quart of trans. fluid in and took off again.
now it won't shift out of 1st gear and has reverse. Think a major problem or minor? I do pull a trailer with it. Its an auto trans. with over drive.

Answer 1

Major. It's time for a rebuild. Next time use Mobil 1 synthetic. It will hold up to the stress of towing a lot better.