Trans shifts at high rpms and 4x4 wont lock
 

Ok, I have an 88 blazer, 4.3, 4x4. The transmission shifts but at high rpms and then with a jerk. The transfer case is manuel and works but the truck will not go into four wheel drive. Maybe its not locking. I suspect vacuum problems to both. Is it a common problem for tranny and 4x4 to not work right? I would appreciate any help with this problem. I just got this truck and do not know alot about Blazers.
Thanks,
Jim

The transmission is controlled primarily by the TV (throttle valve) cable. If it is not adjusted properly, it can cause all sorts of weird things including premature failure of the transmission. Google "TV Cable Adjustment" and you should find a real good write up or two on how to adjust it.

As far as your 4wd, it is a common problem for there to be vacuum issues that cause the front axle to remain disengaged. Check out the Tech Article (DIY) section for more on the 4wd subject.

ok so in other words there is no vacuum to a 1988 blazer 700r trans and no modulator?
Thanks in advance.

That is correct.

Thank You swartlkk

OK, that fixed it. TY SIR!

Glad to help!