Slipping or Clunking in 4 wheel drive

Hi This is my first post.

I have a 2004 Silverado Z71. In recent months especially since winter is here and I use my 4 wheel drive more often whenever I engage the 4 wheel drive system and accelerate there is a loud almost rhythmic clunking, each clunk or click occurs within about 1 sec of eachother... sounds like something slipping and I can feel it in the steering wheel like one of the front tires is grabbing and the other isnt. I recently changed the transfer case fluid because it was toast (almost black). The fluid in the front diff was still a good color and at the proper level.

The issue seems to be worse when turning left. Or at least I think its left might be right... Has been awhile. Been afraid to use my 4x4.

Its hard to tell if the clunking is coming front the transfer case itself or the front drive line. Has anyone had any experience with this type of issue before and what are possible issues to investigate. This is my first 4x4 truck so my experience is limited, for the most part I am capable of doing most repairs myself.

Thanks again I appreciate any insight you maybe able to provide into this issue.

the darker the lube the more the metal that has been worn from the gear teeth...the front tires must be of the same size and wear...operating with tires not matched or all tires not of the same wear WILL result in rapid wear of ALL the drive train componets...

tire rotation is a must with this vehicle....

I suspect that the front diff will need a rebuild...operation of the vehicle in any 4wd position means the front axles are locked as one...turning is difficult on solid dry pavement this is part time 4wd which means you must not operate the vehicle on solid dry pavement in the 4wd position.

What can I do to further diagnose if the front diff is shot?

It sounds to me like the chain has stretched in the transfer case and or the gears are worn

wonderful... Whats better to find a used transfer case or can a person rebuild it fairly easy?

wonderful... Whats better to find a used transfer case or can a person rebuild it fairly easy?

Also, check all the U-Joints & the CV-Joint.

wonderful... Whats better to find a used transfer case or can a person rebuild it fairly easy?

sorry I miss read your original post...the transfercase fluid was black ! this is the clutches ...yes this can be rebuilt...also there is the bushing at the output that should also be replaced.

I would find a repair shop familiar with this drive train componet.
perhaps a dealership that has a good working reputation..

the transfercase takes only tracII GM fluid...do not use tranny fluid......

So I guess if the clutches in transfer case were dead or dying they would slip making this clunking noise?

At first it was only doing it once and a while. I took the truck to Mr. Lube for its "warranty approved oil change" they showed me how black and gross it was and I think they put tranny fluid in... and it has got progressively worse, cant remember if they said it was red or blue.

What would I look for if I buy a used transfer case... anyway to tell if its in good condition?

All the info I could find says for the manual transfer case to use dextron III. I check the bill and that is what Mr Lube put in (atf).

Maybe it was just to far along to recover... Well the hunt for a transfer case begins.

any ideas if a transfer case from the same year 2500 would work?

All the info I could find says for the manual transfer case to use dextron III. I check the bill and that is what Mr Lube put in (atf).

Maybe it was just to far along to recover... Well the hunt for a transfer case begins.

do you have the manual transfercase ? or do you just have the push buttons on the dash type ?

the dash push button type is the trac II blue fluid transfercase type only from gm p/n 123478396 or 12378508 newer number..


they no longer make dexron III...if a transmission requires dexron III like a manual transmission this would use synchromesh fluid..

with the automatic transmissions you would use the dexronVI fluid.

as you can see there have been changes to the required spec of what to use in these drive train componets ...MR LUBE is not the person to trust on this issue..with your vin# call dealership and find the correct fluid to use....If you do have the manual transfercase...this is not that common and I believe that GM does have a correct fluid for the MANUAL TRANFERCASE ....

this still however does not guarantee the MR LUBE will still put in the wrong fluid...the use of dexron III is most likely why this occured ...especially if this had been done before...

replacement of the transfercase fluid in the auto 4wd train is every 30,ooo mi..that is if you don't want problems and are going to keep the vehicle for a longer time.

I have a manual transfer case. (stick on the floor)

I do not know for certain type of ATF was put into the transfer case. It just says ATF on the invoice I got from Mr. Lube.

This was the first time changing the Tcase fluid since I bought the truck used... I put on 40,000 km.

I have a manual transfer case. (stick on the floor)

I do not know for certain type of ATF was put into the transfer case. It just says ATF on the invoice I got from Mr. Lube.

This was the first time changing the Tcase fluid since I bought the truck used... I put on 40,000 km.

the fluid to use with the manual transfercase should be the dexron III replacement which is gm p/n 88861800. this is for the NVG 261 manual transfercase. gm calls this fluid the MANUAL TRANSMISSION / TRANSFERCASE FLUID..THIS IS SPECIALY DESIGNED FOR USE WITH YOUR MANUAL TRANSFERCASE ...

like I said however make , call dealership with the vin # then post back... with this transfercase you must not use the synthetic transmission fluid dexron VI or it will get damaged..

only the auto transfercase with the push buttons uses the trac II blue fluid...

But you may use AMSOIL Torque Drive Synthetic Transmission Fluid (ATD) or Synthetic Universal Automatic Transmission Fluid(ATF) (NVG 261/263 ONLY)

Would any of you guys know what years, makes and models of trucks would use the same transfer case?

All the info I could find says for the manual transfer case to use dextron III. I check the bill and that is what Mr Lube put in (atf).

Maybe it was just to far along to recover... Well the hunt for a transfer case begins.

yikes cold in winnipeg

for next t-case fluid change:
type of fluid depends on which t-case you have. Your truck can have 3 different tcases which all take different fluid. ie. auto trac (blue colour) is for 4button selectable tcase.

easy way to verify your tcase is checking the build codes (RPO)in your glove box:
manual t-case build code is NP2 takes Manual Transmission Fluid, gm Canadian P/N 88861801

auto t-case four wheel drive, NP1 takes auto trac II

auto t-case all wheel drive, NP2 takes dextron III auto trans fluid which have different friction co-efficients than dextron VI. For this reason don't substitute the later dextron numbers (4&5) which is usually acceptable.

One thing I don't do when shifting on the fly is accelerate until the shift indicator stops blinking and the shift is complete.