07 Avalanche with unidentifiable noise

chevrolet
avalanche

#1

i recently purchased a 2007 Chevy Avalanche 4WD (75K miles) and much to my chagrin, in the first week, i detected a noise that has steadily become worse. the dealership (a Chevrolet dealer) has not been able to determine the cause. I’ve had it back four times already. The noise always occurs between 45-60mph (not rpm-related) there is a groaning sound and it is accompanied by a vibration in the steering wheel. it is especially notcieable when going around turns in the road at these speeds. The dealer said it might be related to the alternative fuel management (DOD), but i deactivated the AFM and the noise is still there. I suspected wheel hubs but they checked and said the hubs are fine. The other day as i heard the noise i dropped it out of overdrive down into “3” and the noise suddenly disappearred. All gear shifts are fine, but this was somewhat alarming. im beginning to think this might be related to the transfer case or front differential? any ideas or help? maybe this would be good for “Stump the Chump” ?


#2

No offense, but I suspect you’ve found out why the last owner traded this truck in. Sorry.

I had a similar problem when I bought my current car, which was used. Off the lot there was a clunking noice in the front end. It took the dealer three attempts, but they finally figured out one of the struts was bad.

Good luck to you.


#3

Sounds as if the OD is bad. Can you just disable the OD and check it for noise. Still not good news though. The torque converter would need replaced and that means dropping the tranny.


#4

only way to disable OD is to drop it in “3” and drive it. was hoping to have a good idea of what it is before I sink a few hundred into diagnosing it. estimate I got for transfer case work is ~$2200. UGH! seems like everything related to tranny work is always $2000 or more


#5

my trans temp runs about 190F. is this a normal operating temp?


#6

That’s the normal operating temperature for the transmission.

http://www.digi-panel.com/trannyoil.htm

The noise/vibration might be from the power steering pump. GM has issued a #PIT4208 that addresses a noise/vibration from the power steering pump at 2,000 RPM’s.

GM reports that flushing all the power steering fluid from the system and replacing it with Valvoline SynPower Steering Fluid has eliminated the problem in some cases.

http://www.valvolineeurope.com/english/products/power_steering_fluids/cid(557)

Tester


#7

Thank you tester, i’ll give that a try. I keep praying this isnt a trans issue. all shifts are fine and good and strong. im willing to replace the entire pump to get rid of the noise. this might explain why the noise reacts to tugging on the steering wheel.


#8

Too bad u can’t somehow disable p/s pump and test drive it. But I assume serp belt drives w/p and alt too?


#9

definitely not the p/s pump, definitely not wheel hubs, definitely…the trans is going bad. planetary gear. not a cheap repair at all. 4wd im looking at over $3K to fix. doh!!


#10

Aaaaaah!

The sun gear shell took a crap.

If you’re going to keep the vehicle, have them install the upgraded aftermarket sun gear shell.

Tester


#11

im opting to replace the entire transmission with a new GMcert one instead of a rebuild. they said it has a 3yr 100,000mi warranty. to repair would only replace the bad parts and warranty just those parts. id rather have the whole thing done. tester, would this make a noise louder “under load” like going around turns, or small hills where its still in OD but pulling a little harder?