btitus

My wife drives a 2005 GMC Denali. We've had this vehicle since new and now have 220k miles. We've taken the vehicle in for routine maintenance and have been fortunate to this point that we haven't experienced any major issues. My wife recently pulled up to a red light when she experienced a loud bang. She described it as thinking she had be hit. The bang was followed up by loud chatter and clinking from beneath, the general area of the transmission (which I assumed it was). That was until the wrecker dropped it off at my house and I noticed the transfer case underneath. I actually didn't realize this vehicle had one. One other strange thing I noticed was that even with the vehicle in park or gear I could still move it without resistance. I'm not sure if that detail alone gives the problem away or not but I'm hoping for a suggestion of the most likely problem before taking to a mechanic. I'm not opposed to tearing it down and fixing myself if it's possible and not a transmission issue. Unless anyone suggest against that. Please share any thoughts for a possible problem and suggested fixes DIY or mechanic.. thanks!

03sierraslt

iTrader: (22)

Sounds transmission related. Park pawl sounds broke at least. Is the trans shifter cable attached? Is this a Yukon or Sierra Denali as they have different transfer cases.

btitus

Thanks for the response. It's a Yukon Denali. I haven't physically looked to check the cable, I'm assuming it's connected because I can hear the transmission try to engage when I shift from park. It is a spinning sound with some loud chatter. With limited automotive knowledge I assumed the transfer chain had broken but i don't know what role that would have in the transmission engaging?

kaze_v8

I personally dont feel like its the transfer case chain.
But if it is, when Ive had them go out on me, I initially hear a clunk or pop when im accelerating, and increases as i speed up.
If I go light on the gas, its almost as if it were not there, over time it gets louder since the chain stretches.

Anyways, when its the chain, its usually a popping noise, most heard under hard acceleration.

btitus

That's actually a spot on description with both what happened and what is heard now! I just failed to describe it in those words. That said, could that be the cause of the transmission not engaging? If so, I'm convinced that's what it is.

Is the transfer case a difficult task to remove and service? I lack automotive knowledge but am very mechanically inclined. So if it's a remove - replace - reassemble then I'll probably do it myself. Your thoughts?

kaze_v8

Honestly it can be one of two things, if not both.
The chain can just be worn out due to time, these things stretch and need to be replaced every 60k miles if im not mistaken. Secondly, these transfer cases are known to have the chain on the pumps end rub a hole through the TC.
If that happens then youre gonna need an entire new TC, if not, and its just the chain, then Id replace the chain which is lik 80 bucks on ebay, and buy a case saver which is like 20 bucks to prevent the chain making a hole through the case.

If you've got no leaks either through the input shaft seal or something then Im gonna assume it just stretched due to wear and tear.

Im gonna try looking for the rebuild thread, but Im tied up at the moment. Its a pretty straight forward fix, Ive done it twice, and i spent more time removing driveshafts and reinstalling, than the time i spent on the TC itself.

01ssreda4

iTrader: (87)

With a decent floor or trans jack they are simple to remove and actually not very heavy either.