i am new to this forum, and new to 4 wheel driving in general. I have recently aquired a 77 blazer with 454. I love everything about this truck so far except that when it is in 4H or 4L and i accelerate hard and the truck meets any resistance (like when climbing a steep rocky hill) I have to hold onto the 4 wheel shifter lever to keep it in 4 wheel drive. In 2 high I have no such problem. Can anyone diagnose this for me and tell me what i need to do (parts, etc) to fix?
Thanks,
Adam

 

What do you have for a transfer case? Stock for a 77 automatic transmissioned Blazer is an NP203 while for a manual transmissioned truck, it would be an NP205. However, since the 454 was not an available factory engine for this year, all bets are off as to what has been done to the rest of the drivetrain.

The most common cause of this is the linkages being out of adjustment. I cannot run through it right now, but I know the Haynes manual details this somewhat decent.

It is also possible that either the range fork is bent or the range select bushings are bad. It is also possible that the transfer case mount is bad allowing the shift lever to hit on the transmission tunnel, popping it out of gear. This can be worse if a body lift has been installed on the truck.

 

thanks for the qick response, i am very new to 4 wheel drive and was hoping for an easy, do it yourself answer. I will take your suggestions amd work through them.

 

Again, I am sorry that I could not detail the alignment procedure. It is always a good idea to have some kind of a hard copy manual for your truck. I have all of the factory manuals and the Haynes manual for my 74 K5 and would not have it any other way. Great information and typically very good pictures. Without the pictures, sometimes the directions for these types of tasks are hard to follow.

 

Have you purchased a manual for your truck? Even the Haynes manual goes through the proper adjustment procedure for the NP203 transfer case. As said, you should have a repair manual if you want to work on your truck...

A quick google search for "NP203 Adjustment" came back with the following:
But do remember to remove the blocks from in front of the wheels!