1997 Blazer LT replaced the brake booster after it sat for about three months. It was parked on a slight incline with the rear lower than the front. After reassembling everything the shifter moves through all the gears but transmission won't engage. Every gear except Park is like neutral. Put it in neutral and it did roll backward when pushed out of rut. Any ideas where to start?

 

Have you checked the trans fluid level? It's possible that the seal between the transmission is bad and allowed the trans fluid to leak into the transfer case. Sitting in the position you described could allow enough to leak out to keep it from engaging.

 

Also check the shift cable at the transmission...just to be sure that it is intact.
jck1961 is likely on the right path; if the fluid did not leak out, could just be that the trans fluid is at the rear of the pan and little in the trans pump. May have to pull the Blazer to level ground.

 

Thanks jck1961 that's what it appears to be. I feel silly for not checking that first, but after adding transmission fluid it works. Thanks for both replies.

 

Glad I could help ! You'll need to drain the extra fluid from the transfer case or it will get sucked into the vacuum lines and cause more problems. Just remove the fill plug and have a large pan ready.