Chasing a clunk in the front end

[TowGMC]

I picked up this '09 Denali with 31,000 miles in February. It'll be my backup tow vehicle, as well as an occasional family vacation SUV.

I've been chasing a clunk in the front end since I got it, been to the dealer 3 times and so far no resolution.

Only happens after coming to a full stop at a light, stop sign then pulling away. As soon as I step on the gas to pull away, the nose lifts and I get a very noticable clunk in the front end, also felt in the floor by the pedals. First trip to the dealer they "lubed" the drive shaft, no good. Second trip they "checked the torque" on all front suspension components. Again, no change. Denali is in the dealer again this week, and now they're saying it's normal and they all do that. I know that's BS, I travel extensively for work and have been in probably 30-40 rental Yukons and Tahoes over the past year and not one of them did this.

So I'm hoping some of you might have some ideas? To me it sounds like a dry left front shock but dealer says no, so until they agree I can't get warranty to cover a shock replacement. Ideas??

 

[Northern Ont]

I'd say that you are on the right track with the shock, but it could also be a missing or loose rubber on the stabilizer bar, stabilizer bar linkage or bottom of the shock on that side... Do you hear it on bumps too, or just on take off?
I think the stabilizer bar would clunk over any bump too, especially if one wheel hits it and the other doesn't.

If you just rock the vehicle by hand, can you reproduce it for the dealer?
Those intermittent problems are a real pain in the butt.
Hope this helps.

Rob

 

[southboundchicken]

definitely check all the bushings up front , you might want to remove the shock in question and check it for yourself if the dealer says no...

 

[domin8]

I'm having a similar situation and have been told to inspect the front sway bar bushings at the frame by a good friend that is an engineer and does consulting for GM on occasion. As soon as I get a chance I'll look into this. I'm hesitant to order because it is a special order part through Moog. If what I see turns out to be the sway bar frame bushings I'll definitely let you know.

 

[InTruckDesign]

Just because it was at the dealership and they said they checked all front suspension parts doesn't mean they did. I'd grab some wrenches and double check, sounds like a loose shock to me, or as you said a dry bushing...spray the suspect bushing with some lube and see if anything changes.

 

[TowGMC]

Thanks everyone.

Normally I'd have gotten under the front of the truck myself but the last month has been crazy busy with business travel so it's been easier to just drop the Denali at the dealer, after all that's what a warranty is for. But if it comes back again this afternoon and they say they can't find anything I'll get it up on ramps and take a look this weekend.

Northern Ont- It only happens once on takeoff. No clunks over bumps. That's why I originally thought a dry shock. Plus when I do hit bumpy potholed stretches of road it feels like the front shocks aren't dampening very well, but after driving a BMW X5 with Bilsteins and H&R springs everything feels underdampened.

domin8- I considered the sway bar bushings, but have a hard time believing they'd be bad after just 31,000 miles. Still, worth checking.

 

[GM Customer Service]

TowGMC,

Other things to consider is the rear drive shaft/slip yoke. This is just a suggestion, not a diagnosis. Please keep us updated as to the result of your dealer visit.

Louis
GM Customer Service

 

[TowGMC]

TowGMC,

Other things to consider is the rear drive shaft/slip yoke. This is just a suggestion, not a diagnosis. Please keep us updated as to the result of your dealer visit.

Louis
GM Customer Service

Thanks Louis. That's the first thing the dealer tried, and for a fee since it's not covered by warranty. But it didn't make a difference.

 

[domin8]

domin8- I considered the sway bar bushings, but have a hard time believing they'd be bad after just 31,000 miles. Still, worth checking.

This wouldn't be a mileage issue. It would be a time and weather issue if the bushings are the culprit.

 

[InTruckDesign]

Thanks Louis. That's the first thing the dealer tried, and for a fee since it's not covered by warranty. But it didn't make a difference.

Holy Crap, that is some ******** right there...so much for a 5yr/100,000mile drivetrain warranty...I'd be writing GM a letter on that.
I know it is not common on the nnbs/GMT900 to have the slip yoke clunk like the nbs/GMT800's did, but what is a drivetrain without a driveshaft/slip yoke??