No 4x4...

[hsak]

2000 Silverado Z71, 4.8L, 4L60E, 246 GM (Push Button).

Noticed (inconvienently) that my 4x4 had quit working awhile back. Checked the actuator on the front diff and sure enough it wasn't engaging. Replaced actuator and visually confirmed it was functioning.

Still no 4x4. Noticed lights on Push-button switch would sometimes go out, replaced switch, lights work great now, still no 4x4.

Had someone push buttons on 4x4 switch while I was under truck, I can hear/feel the "encoder" motor turning. When truck is on jack stands, front wheels begin to turn when you attempt to use 4x4, but if they are held by hand they stop while rear tires continue to turn.

If I try to drive in 4x4 in slippery conditions, the "Service 4x4" light will come on intermitantly, and will not go back into 2HI until ignition is turned off/on.

At this point I'm assuming the clutch is burnt out, but a guy at a local tranny shop told me that it could be the fork assembly. He mentioned something about pulling the encoder motor and watching to see if it is working. For what its worth I will probably just end up pulling the entire transfer case and splitting it open for a look. Was just wondering if anyone had any other ideas, other then the clutch. (A cheap and easy fix would be great!)

[Silverado6x6]

I think mine may be different its an 02 3500, Allison, dealership swapped out the panel switch module said it was an issue.

[hsak]

***UPDATE***

Checked the oil in the case, its pitch black like burnt motor oil. You can also here the encoder motor/fork making a clinking noise when you shift from 2HI to 4HI. This leads me to believe the fork assembly/motor is good, and the clutch is finished?

[Silverado6x6]

I'm sorry but what goes on in the transfer case of the new Chevs is beyond me, I have rebuilt many years ago but things do change. Sounds to me like an incompatibility of oils going on there, I do know the transfer case on my 02 3500 requires the SPECIFIC GM fluid, if you or someone else like a low paid oil changer may have mixed in 90w or regular ATF and THAT will gum up everything. Ask again in a specific forum or start a new thread for more insight on that. A cheap fix? dunno but changing the fluid may be a first step though it would have to be drained out again if you crack open the case, sounds to me offhand of a bad bearing. There is one thing I have seen though it may not apply here is a friend of mine with an 01 2500HD 6.6 while coming up the alaska highway lost a bolt on the crossmember at the tranny, broke the adapter housing of the case and tranny right off, check for any cracks?
Get an expert and find out about the proper transfer case fluids first.

[hsak]

Originally Posted by Silverado6x6

I'm sorry but what goes on in the transfer case of the new Chevs is beyond me, I have rebuilt many years ago but things do change. Sounds to me like an incompatibility of oils going on there, I do know the transfer case on my 02 3500 requires the SPECIFIC GM fluid, if you or someone else like a low paid oil changer may have mixed in 90w or regular ATF and THAT will gum up everything. Ask again in a specific forum or start a new thread for more insight on that. A cheap fix? dunno but changing the fluid may be a first step though it would have to be drained out again if you crack open the case, sounds to me offhand of a bad bearing. There is one thing I have seen though it may not apply here is a friend of mine with an 01 2500HD 6.6 while coming up the alaska highway lost a bolt on the crossmember at the tranny, broke the adapter housing of the case and tranny right off, check for any cracks?
Get an expert and find out about the proper transfer case fluids first.

You know, come to think of it I think I topped it up a while ago unknowingly, with 80W90. I was reading other threads relating to these transfer cases and they had mentioned that the tranny and transfer case use ATF. It never even clicked with me. Although that can't be my problem since no one has touched my truck but me since I bought it from the dealer, and this problem occured before the top up. Definately an eye opener though, I found a used clutch in good condition off ebay for 50$ aswell as a drive chain and oil pump. Would have been a pretty big piss off to wreck the newer clutch with the wrong oil!! Thanks!

[Silverado6x6]

I learned this when I mixed ATF with GM power steering fluid, got black and gummy. You can also get a real mess in the old days if you were to mix mineral oil and conventional 90w, turns into a tar. Technology is becoming a real standard of more precision of parts unheard of 50 years ago. Looser tolerances back then did not need exotic fluids case in point like gear oils, nowadays its the least understood part of owning a vehicle, I have done heavy equipment oil tests that can tell us almost to the exact part what is wearing prematurely, I suspect in those tight tolerances you are all gummed up internally. Now if this was my job to repair I would say a complete teardown is at hand to completely clean everything, a complete case wash, I do not think just adding new oil will fix it, but you could try it, and maybe repeat draining and a refill. Good luck!