2006 Denali Transfer Case Howl

[easterr]

Hello,

My 2006 Denali with 90K miles has begun to make a vibration on deceleration at about 35 MPH. From tons of google and forum research, the symptoms seem indicative of a front differential issue. Took it to a mechanic and put it on the lift. He then put it in gear and accelerated. At first, only the rear wheels turned and then as the speed increased the front wheels began to turn - I assume this is due to the 60/40 power split. There was a very loud howling type noise from the transfer case, that seemed to be transmitted through the drive train. Now that I heard the noise, when driving home from the shop, I think i was able to hear it when accelerating.

Transfer case fluid was changed a year ago and was full. Does this mean the transfer case has to be replaced?

Also found a brake hydroboost leak from the internal seal where it meets the master cylinder, so the hydo has to be replaced also. Wasn't a good visit to the shop.

Thanks very much in advance.

 

[easterr]

Hello,

After doing some reading, should all wheels spin when on the lift? Seems in some cases they do and in others they do not.

 

[cmc76]

from some reading i have done, there is a pretty common wear point where some component wears through the case. I know they make a product to protect it, but requires splitting the case.

 

[Rocket Man]

from some reading i have done, there is a pretty common wear point where some component wears through the case. I know they make a product to protect it, but requires splitting the case.

In that instance, though, you lose all the fluid and the problem is obvious I believe? At least from what I remember.

 

[cmc76]

once it wears through. i think the noise is symptomatic of the early stages. Has not happened to me. But ive read of a few cases of it.

 

[easterr]

Thank you, guys. The noise from the transfer case sounded like a bearing noise. Can that indicate the wear point you mention?

Also, should all 4 wheels spin when on the lift?

Thanks again

 

[easterr]

Thanks. After more reading, I don't think the wear point you mention applies to the Denali AWD transfer case? I've also learned that the Denali should not be driven when on a lift and will make a loud noise bc the bearings or gears are over-revving. However, I assume all 4 wheels should spin when on the lift? Makes sense, but haven't actually found a discussion that clearly states this.

I have done a lot of reading bc the vibration and slight grinding seem to be the differential, but if all wheels don't spin on the lift, then that seems to indicate a bad transfer case, which is what 2 mechanics have stated, but both are experienced mechanics not tranny specialists. Just a bit confused with all the AWD transfer case info I have read.

Thanks again

 

[Rocket Man]

When I had my Corvette servo installed they had it on a lift and had it shift through all 4 gears and all 4 wheels spun.

 

[easterr]

Thank you. This is very helpful.

 

[easterr]

Thought I'd reiterate for future purposes, that according to the BW specs for the 4481, truck shouldn't be run when on the lift.