99 Blazer with NP236.

I am trying to diagnose a noise when 4wd is engaged.

Jacked up all 4 wheels, so I could engage 4wd and let wheels spin and crawled under blazer to try and locate noise.

Noise is not constant, but occurs 1x per revolution of front drive shaft, it is coming from or very near the shift motor housing on the TC.

When 4wd is disengaged, the noise stops.

Also checked the vacuum actuator for front axle and it is working fine.

Any ideas on what is causing the noise?

Chris

 

I would check the CV axle boots, check fluid level on front differential, check fluid level on transmission. If I had to guess, I'm thinking it's a bushing that's going bad. Try to move the yoke going out of the transfer case up and down and side to side, do the same thing for the yoke in the front differential. If there is any play at all, the bushing is probably bad.

 

I checked the front drive shaft for play at both ends, did not find any side-side or up-down movement.
Also checked fluid level in TC, it is right at the top.

All drive train fluids / filters were changed out 2 yrs ago.
I only drive about 10k miles a yr.

 

I talked with mechanic friend today, explained the noise coming from TC.
He said the TC noise issue could be a few things, won't know till it gets pulled and opened.

Vehicle has 214k miles on it, 4wd does not get used much, except in winter and pulling boat up steep landings.

Looking for recommendations on these options:
1. repair or rebuild existing TC
2. buy used TC and swap it out
3. buy rebuilt TC

Chris

 

Anyone have experience with this issue ?

Did you find it more cost effective to repair Transfer case, replace with used or rebuilt?