Clunk when leaving a stop.

[PatDTN]

When I accelerate from a stop I feel and hear a clunk. Also while driving down the interstate I notice it is twitchy. Every now and then it will change trajectory slightly requiring a correction to keep going straight.

I was pretty confident that I had a bad bushing in the rear suspension that was moving around. A friend has a nice lift and we put the Tahoe up on it. All the various parts of the rear suspension are solid. There are no rub marks to indicate movement outside the norm and a pry bar applied at angles can't move anything.

We pushed and tugged on the rear wheels without finding any looseness. We checked the driveshaft just in case and can't find anything there.

My friend watched closely from outside and couldn't see anything going wrong.

This is a 2009 LTZ with 200k miles. I have no idea what else to check.

 

[HiHoeSilver]

When I accelerate from a stop I feel and hear a clunk. Also while driving down the interstate I notice it is twitchy. Every now and then it will change trajectory slightly requiring a correction to keep going straight.

I was pretty confident that I had a bad bushing in the rear suspension that was moving around. A friend has a nice lift and we put the Tahoe up on it. All the various parts of the rear suspension are solid. There are no rub marks to indicate movement outside the norm and a pry bar applied at angles can't move anything.

We pushed and tugged on the rear wheels without finding any looseness. We checked the driveshaft just in case and can't find anything there.

My friend watched closely from outside and couldn't see anything going wrong.

This is a 2009 LTZ with 200k miles. I have no idea what else to check.

Common for the u joint to do that. You didn't see any play there, huh?

 

[PatDTN]

Common for the u joint to do that. You didn't see any play there, huh?

No, my friend builds race cars and we both have lots of experience. No movement in the u-joints. Surprising with the high mileage.

 

[shreksbrother]

When I accelerate from a stop I feel and hear a clunk. Also while driving down the interstate I notice it is twitchy. Every now and then it will change trajectory slightly requiring a correction to keep going straight.

I was pretty confident that I had a bad bushing in the rear suspension that was moving around. A friend has a nice lift and we put the Tahoe up on it. All the various parts of the rear suspension are solid. There are no rub marks to indicate movement outside the norm and a pry bar applied at angles can't move anything.

We pushed and tugged on the rear wheels without finding any looseness. We checked the driveshaft just in case and can't find anything there.

My friend watched closely from outside and couldn't see anything going wrong.

This is a 2009 LTZ with 200k miles. I have no idea what else to check.

Hello, have you considered the motor mount?

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[PatDTN]

Hello, have you considered the motor mount?

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I read about those and I'm considering that. I need to get some more lift time with my buddy but he's always busy.

Thanks.

Pat in Tennessee

 

[shreksbrother]

I read about those and I'm considering that. I need to get some more lift time with my buddy but he's always busy.

Thanks.

Pat in Tennessee

No need for a lift to check that... Need to look under the hood while someone hits the gas in drive (obviously their other foot needs to be on the brake). Just watch for the motor to move a couple of inches with torque.

Replacement isn't really a job for a lift... You can do it with a couple of jacks and some basic hand tools.

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[PatDTN]

No need for a lift to check that... Need to look under the hood while sometime his the gas in drive (obviously their other foot needs to be on the brake). Just watch for the motor to move a couple of inches with torque.

Replacement isn't really a job for a lift... You can do it with a couple of jacks and some basic hand tools.

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I should be able to work that out. We'll see. Again, thanks.

Pat in Tennessee

 

[iamdub]

^^^ What Adam said. I had the hood up and, from the driver's seat, watched the motor (actually the beauty cover) through the gap between the back of the hood and cowl. Just do some light powerbraking and see if the motor jumps up and slams back down when you get off the throttle.

A bad motor mount will have nothing to do with the steering being twitchy. This is likely slack in the steering or front suspension. A worn steering rack is the least likely culprit. Worn inner and/or outer tie rod ends is a little more likely, but they'd have to be dangerously worn to have enough slack to cause sudden and drastic enough changes that you could feel. If the control arm bushings are badly worn, the arms can shift forward and backward when accelerating and braking. This can cause noise, looser steering feel (you may not notice this since you're "used to it"), and wandering due to the alignment constantly changing. With such a heavy vehicle, you may not be able to replicate the forces enough to see the slack. Idle backwards in reverse and jab the brake to come to a stop and continue to hold the brake firmly- you'll probably at least hear a clunk but that could just be a little slack in the brake calipers and not what you're trying to track down with this test. The point is to shift the front suspension forward to reveal slack. While still holding the brake firmly, shift to DRIVE and sharply jab the throttle while someone watches and listens from the front wheel arch. This will have to be someone that trusts you to not let off the brake and roll away. Have them closely watch the gaps between the control arm bushing(s) and frame mounts to see if the arms move backward when you try to jump forward. Continuously holding the brake after you reverse is important because you're using them to keep everything loaded in the opposite direction from normal driving. The cool thing with the control arms is that you replace the whole thing as one unit- arms, bushings and ball joints. They're a quick bolt-on repair so you can kill two birds and get stoned.

 

[iamdub]

I tried twice to edit my last post mentioning worn shocks also being a possible cause for noise when accelerating but was temporarily blocked from the forum. I'm not gonna type it all out again. But, yeah...

 

[PatDTN]

All great advice. I'm betting some part of that will pinpoint my issue. My buddy and I were convinced the noise was in back but we eliminated that so forward it is. Thanks. I will update with what I find when I find it.

Pat in Tennessee

 

[thompsoj22]

Transfercase planetary? are your tires all evenly matched in size and pressure? Allthough pressure difference would have to be dramatically low/high so not likely. The transfer case design keeps all wheels driven all the time and has a planetary that allows stabiltrak to do it's thing. If the planetary were failing it could be creating a drag on the front diff and giving you that wierd steer problem and would be making noise as it is about to grenade. just a thought, have the tires allways been matched in height?

 

[PatDTN]

Transfercase planetary? are your tires all evenly matched in size and pressure? Allthough pressure difference would have to be dramatically low/high so not likely. The transfer case design keeps all wheels driven all the time and has a planetary that allows stabiltrak to do it's thing. If the planetary were failing it could be creating a drag on the front diff and giving you that wierd steer problem and would be making noise as it is about to grenade. just a thought, have the tires allways been matched in height?

Mine is a Tahoe with 4 wheel drive, not AWD. But at any rate all my tires are matched and the pressure is spot on. Thanks for the thought though.

Pat in Tennessee

 

[sneasle]

I'm having a similar issue, but my 'clunk' is also accompanied by some hesitation.

When pulling away from a stop (sometimes), I'll feel the truck hesitate a bit (it does start to move, just not at the rate I'd expect), and then I'll hear a clunk and feel a jerk from the driveline as it surges forward a bit and then starts to pull normally. I find that coming to a harder stop is more likely to cause it on the re-start. I also find that I can prevent it from happen by pulling away from the stop very slowly.

Originally I thought that the slipjoint in the yoke/shaft might be binding, but I'm not sure on that anymore. Might be a u-joint? Could it be the dreaded cracked-engine-mounts-of-doom? I'm also fearful that my 1st gear might be slipping, though I'm not sure how to test that.

 

[bladenbullet]

sounds like suspension but i wouldnt rule out a sticking driveshaft slip joint at the trans either...something like that normally wont change trajectory but if it is binding it can create a torque condition....remove the driveshaft and grease the splines...

i would be concentrating on suspension pushings and the park test with someone looking underneath while torquing in drive and reverse might reveal something...also driving around someone in right circles and left circles torquing on and off the accelerator might aggravate the problem enough for them to see something shift...

hanging on a lift might load an otherwise loose component and make it hard to find play in a position it isnt in when the suspension is loaded...

 

[01subCT]

Check your body mounts.my 01 suburban has the same noise an happens the same way yours does.i found a bad body bushing by the drivers door.the lower part of the bushing was pretty much gone the there was quite a bit if movement.could make it feel alittle loose from side to side I bet too

 

[PatDTN]

I hear ya on suspension droop on the lift but generally if things are loose you find some shiny bits at the bushing locations. Worth revisiting with it sitting on its wheels somehow.

I'm not ruling out anything until I find the problem. There's nothing,more expensive than ignoring one thing and fixing something that doesn't need to be fixed.

 

[George Hoffman]

You might want to check either a, your rear end gears might be going out, that's what happened to my 2000 Z71 or b, make sure the U-bolts securing your rear end to the leaf springs aren't tightened all the same amount of threads and torque.

 

[kbuskill]

You might want to check either a, your rear end gears might be going out, that's what happened to my 2000 Z71 or b, make sure the U-bolts securing your rear end to the leaf springs aren't tightened all the same amount of threads and torque.

07-14 NNBS (which is the section you are posting in) have coil springs in the rear.

 

[PatDTN]

Thanks for you guys keeping my thread alive. Sorry life keeps getting in the way of chasing this. I do promise to update this when I figure out what I'm feeling. I'm leaning toward the engine mounts.

 

[Rocket Man]

Me too.