Unknown CLUNK

JCedar · December 16, 2004

Hey guys, in my 99 GMC NBS Short Box extended cab, I have a BIG clunk or a POP noise comming from the front end but I can actually feel it in the floor boards. It feels as though someone took a hammer and cracked the floor boards. The weird thing is that it only does it when it's cold. During the summer months it is unnoticable. I have had it in the dealership they don't know, and the local repair shop that my dad goes thru, he said it was the yoke and I needed that new nickle plated one. BUT I just don't think that's what it is, I don't understand why it would be doing that ONLY when it's cold. I mean even when it's 10 degrees outside if the truck is running for a couple hours it will eventually go away.

Both the dealership and the local repair shop checked all the front end components and said they were all tight, wheelbearings, ball joints etc...

ANY IDEAS would be appreciated

carguru · December 16, 2004

I had something similar, except it was happening all the time on my '02. At first I thought that it was my intermediate shaft acting up again, but I realized it happened every time I hit a bump. Sometimes it is more noticable than others. If you rock one of the corners of the front bumper, it makes a clunk, clunk, clunk noise. It was a combination of things. One of my front shocks were busted. This masked another problem--both of my torsion bar keys were fractured. The dealer replaced the shocks, the keys, the crossmember and t-bars. Problem fixed.

citydriver · December 16, 2004

Loose or busted shocks would be my guess

wisconsinz71 · December 16, 2004

Hey guys, in my 99 GMC NBS Short Box extended cab, I have a BIG clunk or a POP noise comming from the front end but I can actually feel it in the floor boards. It feels as though someone took a hammer and cracked the floor boards. The weird thing is that it only does it when it's cold. During the summer months it is unnoticable. I have had it in the dealership they don't know, and the local repair shop that my dad goes thru, he said it was the yoke and I needed that new nickle plated one. BUT I just don't think that's what it is, I don't understand why it would be doing that ONLY when it's cold. I mean even when it's 10 degrees outside if the truck is running for a couple hours it will eventually go away.

Both the dealership and the local repair shop checked all the front end components and said they were all tight, wheelbearings, ball joints etc...

ANY IDEAS would be appreciated

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If it is happening when leaving a stop start by pulling the driveshaft and greasing the slip yoke. That's what happens on my '00, I do it once a year jsut as the weather turns cold.

carguru · December 16, 2004

If it is happening when leaving a stop start by pulling the driveshaft and greasing the slip yoke. That's what happens on my '00, I do it once a year jsut as the weather turns cold.

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If it is the slip yoke, it wouldn't be felt in the floor boards.

5.3isnota327 · December 16, 2004

The '99's had a bulletin on the front spring making a noise similar to this description. I believe it entailed installing an insulator...I'll have to look to see if I can find the bulletin number.

JCedar · December 16, 2004

If it is happening when leaving a stop start by pulling the driveshaft and greasing the slip yoke. That's what happens on my '00, I do it once a year jsut as the weather turns cold.

I just did that last week, no fix.... thanks for the idea though.

Hey Carguru I sure hope I don't have those problems, I will have to check out the torsion keys, my shocks are getting pretty old and will be replaced soon, I am a college kid though and can't really afford to get my shocks replaced at the moment.

The '99's had a bulletin on the front spring making a noise similar to this description. I believe it entailed installing an insulator...I'll have to look to see if I can find the bulletin number.

I haven't heard of that one, if you could find that bulletin I would really appreciate it.

Thanks for all the help guys

carguru · December 16, 2004

JCedar,

I'm hoping that you don't have that problem either. From what the mechanic was telling me about this, the insulators will keep the bar/keys from hitting the crossmember. The reason they replaced the crossmembers and the torsion bars are due to the severeness of the damage done by the fractured keys. According to my mechanic's theory--first, the shocks went south on me (bottom rusted through and all the pressure and oil leaked out). This forced the torsion bar to work more, which in turn caused it to work the key/torsion bar into the crossmember. The keys had a fracture, but it was not all the way through, the torsion bars were damaged by the damaged keys, and the cross member had witness marks from the contact of the keys/torsion bars. He also said that it was rare to have a fractured key. Even more rare to have both. I saw the parts after they were removed. They were not pretty. Definitely a crack at one of the corners of the hex. Both keys were in the same spot.

The first thing I'd check are the front shocks. Bounce the front end at either corner and see if there is a noise. Inspect the keys. I can get you the part number for the insulators too. They put those on also as part of the deal.

JCedar · December 17, 2004

Okay, I'm going to check it all out tomorrow and see what I find, any part numbers for insulators or any bulletins that have anything to do with a Front end clunk would be appreciated.

Thanks again guys

JCedar · January 1, 2005

Hey guys just wanted to give an update here,

I put new bilstein shocks up front and the clunk still persists. I crawled under my truck yesterday and checked out the T-bars and keys while changing my oil. I didn't notice anything wrong with the keys, but I did notice that the drivers side t-bar is cranked all the way up and the right side has QUITE a bit of room for adjustment. I thought maybe it should be like that for the gas tank BUT, it is cranked ALL the way. Any thoughts on this? And once again the clunk only occurs when it is below freezing out, and when it either is in the process of turning or hitting smaller chatter like bumps. I AM CLUELESS????? Any ideas would be appreciated. Everything up front including ball joints, wheel bearings, pitman arm, everything was checked out by the dealer and local repair shop and nothing was found wrong??????????????????????????

BTW those shocks are beyond awesome!!!!

mcreyaufmiller · January 1, 2005

Could it be a cat or kid trying to get out when you start up oin the mornings?

JCedar · January 1, 2005

Could it be a cat or kid trying to get out when you start up oin the mornings?

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haha funny you should say "cat" because a friend told me that it could be the heat shield above my catalytic converters, he said on his old buick it used to pop or clunk during cold weather and that's what it turned out to be. It kind of makes sense because they are right against the floor boards and I have ruled just about everything else out. One more look at the t-bars and control arm bushings and that's going to be my guess. If it was something serious you would think it would have broken now, whatever it is.

sgiangregorio · January 1, 2005

I had a similar issue just the other day. The dealer took my front drive system apart of fix something else, but greased the yoke to release the clunk. This is in a 2002.

JCedar · January 1, 2005

I had a similar issue just the other day. The dealer took my front drive system apart of fix something else, but greased the yoke to release the clunk. This is in a 2002.

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hmmmm.... well what were the symptoms of your clunk. See mine hits HARD against the floor sometimes, other times it's just is a light clunk... I can still feel it no matter what, but no where near as much as if I let it sit outside all night and it's 10 degrees outside, I did that a lot so far this year and it felt like a baseball bat was slammed against my floor.

gixxer · January 3, 2005

i had a similar problem on my mine, and it would do it when it was cold out. It turned out for me to be the inner fenders werent tight and would move around. The clunk would saound as if it were under my left leg while driving. I even wen as far as changing body bushings to figure that one out.