I have a 2000 4wd 2dr. One morning she wouldn't shift past second gear. i pulled the tranny and took it to a local shop to be rebuilt. I got it back, put it in and had the same problem. the shop told me it could be the valve body. I got mad and put in a new vavle body, tourqe conv., and cooler. Finally i got it to shift into third but it was slipping bad and after a couple miles she went back to having only 1st&2nd. took it back, rebuilt again, same problem. Took it back, now the shop said they found a crack inside the case. And they said sorry we'll get u a new case for free. Got it back-same problem, slips then only 1st & 2nd(i believe safe mode). Now they're putting in a new tranny for free. Is there something i'm (they're) missing?

 

The trani shop should know of any Electrical or Vacuum related issues that will keep this from upshifting. You would thinkk they would have diagnose the heck out of it since now they are doing a lot of this work for free. I can't imagine what the heck is going on.

 

I just stumbled on this. https://blazerforum.com/forum/engine-transmission-35/automatic-transmission-issue-43185/

 

thanks for the input. i took it to the dealership and the service manager told me that pre-2004 wiring harnesses were made with low quality copper. And that i may have broke one (inside the casing)during the removal or installation. I'm gonna call them tomorrow to ask them to check the tranny fuse. I'll keep yunz posted.

 

I finally got it back today. It was 1 streched wire and 1 broken wire in the tranny harness. The wire was broke inside the casing! The broken wire read the pressure in the transmission, which wouldn't let it shift into third, which made it overheat, which glazed the clutches and caused slippage. Glad to have it back.

 

If/when the next time comes, find a different shop that knows 4L60E's inside and out. At least they admitted their failure at trying to fix your problem and replaced the tranny.

 

Yeah ur kinda right. I know i didn't break the wires. He saids he's rebuilt 100's of 4l60e's. But he has one arm so i can't blame him too much for the wires, i know i couldn't pull it off.