I was wondering if anyone could help me with my 4wd on my 2000 blazer 4.3l v6. The 4 lo works but the 4 hi doesn't. Any idea what i may be.

 

Tell us a bit more. For example what do the lights on the buttons do when you try to shift to 4HI? Does 2HI work? Do you have AUTO 4WD and what happens if you try it (if you have it)?

 

Sorry about that I don't got the AUTO 4WD and the 2 hi does work and the 4 lo as far as the 4 HI i push it and then the light on the button lights on should that it is engaged but its not.

 

How do you know 4WD isn't working? You trying this on a lawn or feeling for driveline bind in a parking lot? When you're in 4 LO did you make sure you had 4WD as well as the gear reduction? This is a puzzler... The controller is satisfied (apparently) the transfer case is shifting to a range properly and the front axle is engaged. What's really weird is the front axle being engaged in 4LO but not high. I'm assuming the transfer case end of things is working correctly or you'd have odd acting buttons or some nasty noises. Jack the truck up so both driver side tires are in the air. Start the truck - put the transmission in neutral, transfer case in 2HI and try turning the front drive shaft. (or spin the front wheel by hand and watch the drive shafts) Rear one shouldn't turn, the transfer case should not be locking them together. Try the same in 4 LO and 4 HI, now you should be turning the rear drive shaft as well. Put your foot on the brake and put it in park. Now in 2 HI you should be able to turn the front wheel in the air by hand but if you try turning it in 4HI or 4 LO it should be locked. The tests in neutral will tell us is the transfer case is working right, tests in park will tell us if the front axle is engaging.

 

Thanks ill have to try that out. Just let me get these straight just jack up the driver side of the vehicle as in the front and rear?

About the 4wd drive i got stuck in i thought it was in 4hi but it was engaged. I had a buddy pull me out and then he told me to put it back in and the 4 hi wasn't working but then i put for 4 lo and i was able to drive it out.

 

Correct. Put a jack in the center of the truck so the drivers side front and rear tires are off the ground. Based on what you said the transfer case isn't engaging the front driveshaft in 4hi but try the things I suggested (remember truck has to be running) and let us know the results and well go from there.

 

RonJon

I just try the test that you told me to do. And my findings were the 4lo works in neutral and in park. As for the 4hi it works but the wheels are a little hard to move versus the 4lo, I had to put a little move pressure when I tried turn them in 4hi. When I try it in park the 2hi the front wheel turn and in 4lo and 4hi they didn't. I think I may have a bad 4wd actuator or not sure.


Also, would this test work on a 1997 Chevy suburban and a 1996 gmc yukon.
The 4hi don't work on the suburban but the 4lo does at least that what they told me. As for the yukon, my friend took it mudding and the tranny line break we repair them and the 4wd don't want to engage.

 

Read this thread I think we've reached the point we need to find out if the transfer case controller has any codes in it. Front axle actuation is the same 4LO and 4HI and if it works in 4LO we (me anyhow) have to suspect the transfer case. Possibly it has a code stored in it. I've never tried this because I have the auto transfer case and it won't work for me. Pins across top row of data link connector are 1-8, 9-16 are bottom row left to right.
As to your friends, I don't know what year the full size trucks went to the vacuum actuator for the front axle. For basic performance checking what I suggested works for anything EXCEPT don't ever try it with a locking differential on the rear! (ZR2 blazer for example) or you'll be coming off the jack. I figured that technique out while replacing my transfer case motor and shifting ranges with a wrench to get it to slip on. The sticker said the motor was in 2HI, it was in 4HI. If it doesn't have the vacuum actuator look for a pair of wires going into the front axle next to the pinion and check those. I know GM used to use a thermal/electric actuator on the front end, my buddys old plow truck had one go bad, maybe the wires got caught too if it has that. Look from the passenger side in front of the axle tube going into the differential.