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weird thumping noise on my 07 LBZ classic

Odlaw

Odlaw

Redneck
Messages
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Location
Deep in the woods - near Waldo, FL
Disclaimer for the moderators; I apologize if this is not in the correct area of the forums. I spent ten minutes trying to decide where is should go without getting my hand slapped :hihi: I think this problem is something in the interior (but I could be wrong) - might be suspension - so feel free to move it there if needed.

I get this weird, fast, thumping noise (almost like a vibration) when I run over a rough surface...like the lime rock on my long driveway...... When sitting still, I can hook the bottom side of the brake pedal with my toe and pop it up and down and that's the sound I'm hearing.....but it's not coming from the brake pedal because I can hold up on the pedal (while driving) and the same sounding noise is still there...it sounds like it's coming from the firewall, under/behind the instrument cluster(maybe steering column? ). There is a block with a couple of large electrical plugs on it (directly under the fuse panel on the driver end of the dash) - it was flopping around in the bracket. I shoved some old bike inner tube in the bracket and fixed that problem.

Both front shocks appear to be leaking a little and even though I would like to blame this sound on the shocks, when I roll the windows down you cannot hear the thumping outside.

Anybody else having this problem on a silverado classic?
I'm open to suggestions here...

Thanks
Smitty
 
Are you familiar with the steering shaft clunk that our trucks are subject to? I feel it more in the steering wheel, but can hear it inside as well. It shows up at low speeds when I hit small bumps.
 
Yeah, I have that clunk on my 01 z71. This is different. The rhythm of the clunk is about like hitting a drumstick (one time) on a drum - more like a vibration but with the deep thumping sound. I hope I'm describing this right. On my 01 it's an occasional thump/clunk - when it does it, it's just normally one thump...and it has done that since new.
 
I would put money on the steering shaft. I'm on my 3rd shaft and it's doing the exact same thing you're describing. I also went through 3 with my 04.5 LLY. I just learned to deal with it.
 
Thanks Nick - that's the info I was looking for. I noticed on the carfax report before I purchased the truck, one of the three visits to the dealer was "steering shaft, lubrication". Over the years I've come to the realization that when a dealer mentions "lubrication" in a repair, that translates to "we're either too stupid, lazy or incompetent to actually fix the problem, so we squirted some really thick grease on it". My 01 z71 would always make this awful "mating sound of the humpback whale" when taking off from a dead stop. Took it to the dealer 5 times total. First 4 my receipt said "transmission prop shaft, lubrication" - each time it would last about a month. I found a TSB online and took it to them.....they replaced the yoke per the TSB. Hasn't made a peep in over 7 years.
 
I had the ISS replaced and within 10K the noise was back. There is a white plastic bearing under the dash where the ISS meets the steering column, that may also contribute to the problem. GM has a replacement one part # 88963617. I ended up going for the hose clamp trick to get mine to quiet. Just push the bearing in and throw the clamp over it and tighten. So far no more noise.....

http://www.thetruckstop.us/forum/attachment.php?attachmentid=21432&d=1283283368&thumb=1&stc=1
 

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That's a neat trick. How'd I miss that?...
Well I've never (knock on wood) had a problem with the ISS on mine. They always put the good parts in the GMCs. ;)
 
CtChevy427 said:
I had the ISS replaced and within 10K the noise was back. There is a white plastic bearing under the dash where the ISS meets the steering column, that may also contribute to the problem. GM has a replacement one part # 88963617. I ended up going for the hose clamp trick to get mine to quiet. Just push the bearing in and throw the clamp over it and tighten. So far no more noise.....


By "push the bearing in" are you talking about the white plastic part?

Thanks for the tip
Smitty
Click to expand...
 
Hmm, the plastic part on mine looks slightly different and it's green. And it appears to be seated all the way in the metal tubing. I was looking at it with a light and mirror.....just put on some old work jeans and I'm going back out there and attempt to get my old rear end turned around upside down and slide under the dash and see if I can find anything.

Which part is actually causing the thumping noise? Is the actual steering shaft vibrating inside that bushing?

Thanks again
 
Well, dip me in axle grease and call me slick! I decided to put the clamp around it anyway last night. Drove down my long driveway this morning, had the window down checking out the cows and in the back of my mind I kept thinking "something sounds different in my truck". I closed the windows and it still took me a minute to notice, "hey, my truck is quiet inside....oh, no more rattle under the dash!"' I totally forgot about installing the clamp last night.

Thanks
 
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