99 tahoe clunk after service

[BigLou101]

My problem started yesterday after having my transfer case, rear and front diffs fluid changed. The problem is only on acceleration, it seems like from a stop. you press the accelerator and something clunks the truck bucks a little bit and then it takes off like normal. any input would be appreciated.

[sprucegoose]

Sounds to me like they may have put the wrong fluid in the transfer case. Verify that they used the AutoTrac II fluid (blue synthetic), and that it was filled all the way up to the fill plug on a level surface. I had that driveline clunk in my 98 till I switched over to that. If the TC fluid level is low, it may not be getting up onto the driveshaft yoke and you will get that slip-stick effect also.

There is always a chance that something else was damaged or came loose of course, but that is unlikely. Was the service done at a GM dealer, or just a local garage?

[Reflash]

Does it only do it just after you accel from a stopped position?

most likely...but not definitely, the yoke on the front of the driveshaft is hanging up on the output shaft for the Xfer case. There is a new designed yoke available that will correct it...its nickel plated.

But if you want a cheaper and easier way to permanently fix it...pull the driveshaft and put a super ball in side the yoke and reinstall the shaft. Sometimes 2 super balls are required, but it will work and will eliminate the klunk.

[BigLou101]

local garage and they used regular dexron111 atf i believe i should be able to pull the check plug dip it and see if its blue correct?
and if thats the case where can i acquire some of the autotrac 2 fluid

[j cAT]

Originally Posted by BigLou101

local garage and they used regular dexron111 atf i believe i should be able to pull the check plug dip it and see if its blue correct?
and if thats the case where can i acquire some of the autotrac 2 fluid

get that dexron III out of there fast ....this is gonna damage that transfercase...I would fill and flush after a short period of time to get all that wrong fluid out...

this fluid is more money and you should not pay for their stupidity....

forgot ....only GM dealerships sell this...you will need 2.5quarts approx. fill to bottom of fill hole....

DO NOT OVER TORQUE THE PLUGS!

[BigLou101]

OK i was wrong they used autotrac 2 i checked all levels. everything is full.
All the u joints are tight. It seems like when it clunks i feel it in my feet and it draws the rpms down. So I'm guessing transfer case. Everything has lube. Is there any other cause of this clunk.

[j cAT]

Originally Posted by BigLou101

OK i was wrong they used autotrac 2 i checked all levels. everything is full.
All the u joints are tight. It seems like when it clunks i feel it in my feet and it draws the rpms down. So I'm guessing transfer case. Everything has lube. Is there any other cause of this clunk.

spray the output shaft of the transfercase with wd-40 see if it goes away...if it does then the new fluid has not worked its way into this area yet...this is if the transfercase is the issue..[the drive shaft sticks]..it should slide fwd/rev when starting from a stop...

if it clunks when moving then it is more the U joints..with the rear wheels off the ground, rotate the drive shafts and check for proper movement.....

[BigLou101]

im not sure if its the transfer case or a u joint sticking because it still clunks while the truck has rolled with no throttle. like just letting off the brake no clunk initially but when i press the throttle then it clunks.

[j cAT]

Originally Posted by BigLou101

im not sure if its the transfer case or a u joint sticking because it still clunks while the truck has rolled with no throttle. like just letting off the brake no clunk initially but when i press the throttle then it clunks.

did they remove the rear diff cover....? if you have the eaton locking dif you must have 75-90wt synthetic oil...

most service shops do not remove the rear cover , the debris remains..use of the incorrect fluid is most likely your problem ...

IF IT WERE MY VEHICLE I WOULD REPLACE TRANSFERCASE FLUID , THEN REAR DIF OIL TO DETERMINE HOW THEY SCREWED THIS UP...

[BigLou101]

is it a possibility that it is my drum brakes in the back starting to stick because ive noticed only after a hard stop the clunk is there. ill drain and change both fluids ill check which rear i have it was rebuilt by a different shop i will have to call there and ask what is recommended.thanks for your help jcat

[j cAT]

Originally Posted by BigLou101

is it a possibility that it is my drum brakes in the back starting to stick because ive noticed only after a hard stop the clunk is there. ill drain and change both fluids ill check which rear i have it was rebuilt by a different shop i will have to call there and ask what is recommended.thanks for your help jcat

since you have DRUM brakes I doubt they are sticking...the disk brakes are the type that could do this binding....as I have had to deal with the poor quality metals used ....that caused this on my silverado...

with the rear dif replaced.....if you have the eaton locker this needs a breakin period to properly harden the gear teeth...then after a 2,ooomi breakin replace the fluid and inspect the gear teeth for damage/cracks...

[BigLou101]

ok this weekend ill be changing the fluid in the rear. any additives that i should know about

[j cAT]

Originally Posted by BigLou101

ok this weekend ill be changing the fluid in the rear. any additives that i should know about

if you have the eaton locking dif there are no additives 75-90wt synthetic oil...

only the limited slip dif uses the 4OZ of additive with 80-90wt oil.. GL-5 ...I hope you don't have the limited slip as this is for a car not truck/suv...most have the eaton locker...this is why I asked and stated that they may have used the wrong oil/fluid....you must know what you have first....

[BigLou101]

[quote=....you must know what you have first....[/quote]
how can i tell will there be writing on the rear somewhere?
i managed to find the following numbers
GM D 12 and 5822
no idea what it means the dealer has been somewhat useless

[j cAT]

Originally Posted by BigLou101

how can i tell will there be writing on the rear somewhere?
i managed to find the following numbers
GM D 12 and 5822
no idea what it means the dealer has been somewhat useless

the easiest way to get this is to call the dealership, and with your VIN.#....talk to the parts deptment and ask what fluid you need for your vehicle....on the fill hole of the rear diff the label should say what fluid to use....you said the rear diff was replaced ????? did they put the same diff in or something else ???

the other way is to find the RPO label...i would guess that it should read GT4=3.73 rear axle ratio, G80=locking rear axle

the RPO label should be in the interior /glove box etc...