I just bought this 94 blazer! It's full size with 5.7 I recently had a issue with my brakes locking up which seemed to cause my tranny to slip a bit then all the sudden it won't shift from 2nd to 3d consistently! Runs about 55 at 3500rpms! I'd like to know why it would start to run normally for a short time then back to only 1st and second gears! The fluid was dirty and after she heated up for after a while of tooling around the woods she started working again but only for a short time! Why would it work properly here or there then that's it no moreAny help is greatly appreciated I am about to rebuild and I want to know if it can be avoided

 

Welcome to the forum!

When you get a chance, be sure to post your question to the specific sub-forum so that you can get the answers you need.

But, from what you describe, you might have a slipping 3/4 clutch pack. Check out this video (assuming you have a 4L60E transmission that is):