Transfer Case Problems

Thanks for the warm welcome guys. I am re-posting so as to not threadjack. I also have some more info.

Here was close to what I posted in the other thread:

It is the 4.3L with 4WD. SHe was in 4WD, and then tried to get back out. The system is unresponsive now, no button presses on the dash do anything. The rear differential is definitely locked, as you can feel it when taking corners in parking lots etc. But it is not in actual 4WD, since I can tell by how it handles in the snow and rain.

I am thinking it is an electrical issue, as there was never any problem with the 4WD, it just went in, and then tried to get back out and it is like it never quite fully disengaged and unlocked the diff.

Any advice? I was going to look at the 4WD control box, supposedly behind the passenger side kick panel, and make sure all contacts were clean, and not corroded.

It is an SLT, with the 4-mode Transfer case, model NV246.

So, tonight I am going to check the connectors for corrosion and proper connection on the TCCM, I am also going to also check the vaccum lines to and from the vaccum switch. Where is this located?

Any other suggestions on what to check tonight? I would really love to get another year out of this car, and with a baby on the way, I cant let my wife go through winter without 4WD.

-Paul

Actually, it might be the NV236, I will have to report back when I check it out tonight.

Good on new thread.
Now we can help you better.
We need year and model and mileage.
Does the shift buttons have auro button it?
Any lights on or flashing?
Any check engine or transmission or transfer case lights on?
Check all fuses first thing.
Transfer case ID on back of transfer case.

If a 236 auto shift button.
You will need a transfer case/transmission capable scanner to get codes and test transfer case shifting.
If any code no post bak code no.

Thanks for the fast response

It is a 1999, with 74,000 miles on it.

Yes, it has a '4WD Auto' button

None of the lights on the switches are turned on.

The 'Check 4WD' dash indicator is on.

I assume all of the fuses that need checking are the ones on the main fuse block, or is there an additional fuse block located elsewhere?

Yeah, I think it is model 236, as I have read that is what is on all 1999 models that have the 'auto' feature.

Thanks again!

4WD fuse no 15 in left end of dash panel and ATC fuse in under hood fuse block and check for 12 volts on both side of fuse key on.
If check 4W drive light on you need to get transfer case codes.
Post back code no.
MT

Ok, got some data here.

I was able to get the '2HI' and the '4WD Auto' lights to light. When I press either of the '4HI' or '4LO' buttons I get some clicking from the TCCM, and the '2HI' light flashes, and it never changes over.

The 'Check 4WD' or 'Service 4WD' light is always lit.

The TCCM model is 15154323.

I checked all of the fuses and they were fine.

I disconnected the battery for 2 hours to reset anything that may have needed it. The 'Check 4WD' light turned off until about 2-3 minutes after the car was started.

The good news is that the rear differential seemes to have unlocked through this process, so the car drives MUCH smoother when the '2HI' light is lit. When the '4WD Auto' button is pressed and the light is lit, it corners a bit rougher when doing sharp parking lot style turns.

Any idea on what I should do next?

I will go back outside and re-install the TCCM to see if simply unseating and reseating the connectors does anything.

Thanks a ton guys!

Ok,

More data!!

I went out and plugged it back in.

Car started, 'Check 4WD' light still lit, and it went right into '2HI'

With the car in P, I tried to switch between 2HI and 4HI. When I do that, I hear the vacuum switch on the engine side of the firewall engage, I get no response from the switch panel on the dash, after a second or so, the 2HI light flashes, and then goes solid.

If I switch into 4Auto, I hear the vaccum switch do something, the 4Auto light flashes and then it engages. This is the same as before.

The new part is, that if I idle in Forward or Reverse, I can switch into 4LO, I get a loud clunk from the rear of the car, along with a few relays clicking in the TCCM, and the vacuum switch infront of the firewall. If I am in Park or Neutral, I will hear it try twice, and then it must give up, because all of the lights on the dash switch panel go out, and become unresponsive. I have to turn the car off, and re-start it. THen it comes back up in 2HI, and will switch in and out of '4Auto'

My wife says that all she uses is '4Auto' and '2HI', if this is the case, is there any way to just get the stupid 'Check 4WD' light to go off?

Thanks!!

You need to get it on a giood transfer case scanner and get codes and check shifting.
Post back codes.
On that one the transfer case fluid needs changed ever so often with the gm transfer case fluid.
And sometimes need flushed.
Has the transfer case ever been serviced?

Ok,

I will flush the fluid when I am down there looking at the encoder motor.

How much does it take?

I am hoping that I can just pull out the encoder motor and clean things up and get it to work again.

-Paul

Need codes?

Ok,

I will flush the fluid when I am down there looking at the encoder motor.

How much does it take?

I am hoping that I can just pull out the encoder motor and clean things up and get it to work again.

-Paul

The flush deal and or tsb on it is drain and fill and drive and then drain and refill.
They hold over 2 QT of GM Blue transfer case fluid.
The flush 2 changes will take up to 5 qts.
Fill it up till it runs out the fill plug.
MT