2000 4WD Problem

I have reviewed this message board extensively, but still haven't found anyone having a similar issue that I am with my 4WD.

I replaced the vacuum actuator, the switch on the transfer case and checked the vacuum connections and my 4WD still does not work. When I hit the button to 4WD high or low, it only semi-engages. There is a humming sound coming from what sounds like the transfer case and the truck pulls hard to the right. When I disengage, it takes a good 30 seconds before it SLAMS back into 2WD - I mean, a fairly violent slam.

From what I can gather, all I really have left would be the encoder motor and the transfer case control module. Any suggestions on which one? Any body know where I can find the problem codes for diagnostics on the 4WD?

THanks!

Sorry that no one has taken the time to try and help you here man. I asked a mech at the dealer about this today and he said %95 sure control module. My 2000 is at the dealer at the moment so while there, I asked.

What are the condition of your tires? The reason I ask is I had a similar problem two weeks ago. I had two new tires on the front (one replaced because of a blowout and I put the full sized spare on the other side to match them up) 13mm of meat on the front while the backs only had 6mm each. The dealer told me mine was having problems engaging and disengaging because of the difference in size from front to back (we are talking mm's here) I did not believe them, but got two new tires for the rear as winter is coming. Believe it or not, it shifts in and out of 4WD with no problem now. If you want to test the distance travelled yourself, lay a chalk mark at the top of the tire on the sidewall in the same spot on all four tires. Then move the truck forward 20 yards or so and see if the lines are still all in the same place. If not, your tires are not all turning with the same diameter.

That humming sound is from the transfer case is the Transfer case motor that is controled by the TCM Transfer case control module.
Check and make sure all the wires are clean and tight. Check all grounds

I really appreciate the feedback. My next step is to try and connect to the ECM to see if I can get a reading on the condition of transfer case control module and the encoder motor.

Interesting concept on the tires. I will have to check that out as well...just in case.

This forum is pretty darn helpful! It's nice to see that I am not alone with some of the common problems with Blazers (have done ball joints, oil cooler lines, wheel bearings, idler arm and now, 4WD).

That humming sound is from the transfer case is the Transfer case motor that is controled by the TCM Transfer case control module.
Check and make sure all the wires are clean and tight. Check all grounds

Hello -New to this Forum. Having something like kirmml's posting above. Our Blazer is stuck in 4WD High or 4WD Auto. But thats it... Parts dealer said the switches on the dash sometimes go. Which sounded odd. You can hear the relay under the dash for about 20-30 secs when you try for 2WD & the humming from the transfercase. (Tried Park, Nutral, reverse... everything) - then it goes back to 4WD hi flashing or Auto 4WD. TCM do you think... ? If it iis, due to the cost... Can a guy just disconnect the electrical plug... Then will it go back to 2WD manually as a temp. fix? It's my wifes unit & I don't want her driving all over in 4WD - Thinking thats going to wear the hell out of everything - Dry roads here right now. Also I saw some posts on tires... It has about 50% Tread on the fronts & 95% on the rears. I'm thinking thats not helping matters.

Thank you if you have some ideas on this.

I have reviewed this message board extensively, but still haven't found anyone having a similar issue that I am with my 4WD.

I replaced the vacuum actuator, the switch on the transfer case and checked the vacuum connections and my 4WD still does not work. When I hit the button to 4WD high or low, it only semi-engages. There is a humming sound coming from what sounds like the transfer case and the truck pulls hard to the right. When I disengage, it takes a good 30 seconds before it SLAMS back into 2WD - I mean, a fairly violent slam.

From what I can gather, all I really have left would be the encoder motor and the transfer case control module. Any suggestions on which one? Any body know where I can find the problem codes for diagnostics on the 4WD?

THanks!

Hi - just wondering how your making out with your problem?

The encoder motor sounds to be the problem.

Also, NEVER switch to 2WD when accelerating.