08 Tahoe transfer case issue

[Hay Dude]

My trusty beloved Tahoe developed a problem
2008 LTZ with 217,000 mi
When I engage the rotary knob into auto mode , I get a loud clunking sound sound while rolling down the road. Switch back to 2WD and it goes away.
Seems like transfer case. Someone said t case needs a special oil....
Ideas anyone?

 

[34Willys]

The 'auto' 4x4 transfer cases take GM TRAK II fluid. It's blue in color as opposed to the normal Red fluid. There's a fill and drain plug in rear of transfer case. Plugs may be aluminum, so be gentle. Sometimes hard to access due to exhaust or cross members. Fluid should be just at bottom of upper fill hole.
Check front driveline and differential/CV shafts also.
Patrick

 

[nisaacs]

Like 34 said, check the front real good. I would also drain the t-case and inspect the fluid.

 

[Hay Dude]

The only serious issue I had with the vehicle was the front axle went at 125,000, but it didnt make the noise I hear now. I replaced it from a donor truck for right about $1,000. Worked fine for 100,000 miles.
This issue seems different.
I dont know now if its transfer case of front axle.....

 

[dodge man]

I thought GM had a problem with high mileage vehicles getting slack in the chain, even to the point it will wear a hole in the Tcase. Does yours have this style?

 

[Hay Dude]

I thought GM had a problem with high mileage vehicles getting slack in the chain, even to the point it will wear a hole in the Tcase. Does yours have this style?

I had heard about that and what’s funny is the sound is almost like the sound/feel of a chain jumping.

 

[RustyA]

Check front driveshaft u-joints/cv joint for excess end play. Especially if noise and vibration is under driver's floor. Transfer case turns all the time. Front shaft only turns in 4wd.

 

[Hay Dude]

But doesn’t the front dive portion of the transfer case output shaft run only when engaged in auto or 4wd? That’s when I get noise.

 

[4570Man]

I’m not 100 percent sure but I think the front wheel drive components remain linked to the front wheels and spin all the time including the transfer case output with the only difference being the inside of the case linked or not.

 

[Hay Dude]

I’m not 100 percent sure but I think the front wheel drive components remain linked to the front wheels and spin all the time including the transfer case output with the only difference being the inside of the case linked or not.

That’s what I mean, when I dial up “ auto “ or “ 4x4 “ on the rotary knob, thats when the fun starts. Random clunking. That’s why I was thinking T case

 

[zilla24]

Have you checked the universal joints? I had a bronco years ago that when the T case engaged the front driveshaft it would clunk like crazy. I initially suspected the T case to be bad and it turned out to be a universal.

 

[Lineman North Florida]

Have you checked the universal joints? I had a bronco years ago that when the T case engaged the front driveshaft it would clunk like crazy. I initially suspected the T case to be bad and it turned out to be a universal.

X2, the universal joints would be my first move, they can make some awful clunking sounds and make you think that there is more of a problem than there really is.