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Cannot trace this noise (front end)

K30Blazer

K30Blazer

1/2 ton status
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I have a really annoying rattle, thud coming from my front end. I have noticed it for ever but have never been able to find it. It is something pretty heavy as you won't notice it going along the road unless you hit a pretty serious pothole. Going over a speedbump at more than 5 mph will cause a heavy thunk.

I was wheeling the last weekend and came down this super steep and slick hill. Pretty much slid the truck down it but had the front end loaded up pretty good. Towards the bottom heard a loud pop / clank / thud. Checked extensively under the truck and couldn't find anything alarming. Reproduced the sound a couple of times though with my friend watching and nothing looked out of place to him.

I have just put new springs on and rebuilt the hubs. Everything I can see is tight and operational. The front Driveshaft ujoints are going but the noise is of more "weight" than that. I do have a swaybar in and the bushings in it are shot and squeezed out to one side. I am thinking that that could be contributing to the noise. I will be pulling that off soon and seeing if that helps.

In regards to the noise, I had a motor mount go bad once and the sound my truck made going over speedbumps with a bad motor mount is similar to how it sounds now.

I put it up for the experts, anything that you can think of that I should check? Steering box is tight and frame is not cracked either.
 
Could be that one or more of the frame rivets are loose. I have seen it before, but it is a hard issue to find.
Have you rechecked your motor mounts?
What about the radiator bouncing around?
 
radiator is tight, motor mounts are good. I was thinking it could be one of the rivets too. It sounds that heavy.
 
i have seen the stock rivits for the frame mount crossmember just in front of the motor go bad. and or the crossmember its self will crack.
 
Could be a spring eye bolt. My neighbors moves up and down a little from wear in the front hanger. I have never heard his make noise though.

Have you ever had a crack in your frame that may have re-cracked, but may not be visable?
 
thanks for the tips. I will check those out tomorrow if the rain stops and report back.
 
Does it only make the sound in 4x4? My 89 Burb just started doing this and I am pretty sure it is coming from the TCase but the sound from the driver's seat appears to be coming from the front end. I am having the TCase looked at next week. (pop and thud not present when in 2x4).
 
could also be...

Might be the splined section of the front driveshaft binding up during its extention/compression while going over bumps..check for loose splines or slop in the yoke,and make sure its greased good..and see if both rubber "bump stops" are there..should be 2 of them on the passenger side,if the rearmost one is missing,the front driveshaft could possibly kiss the starter ...shocks could have a bad spot in the piston travel internally too..sheared center bolts in the springs..shackle bushings..sway bar bushings..ball joints..cracks in the frame at the steering box, etc,...could be the cab mounts creaking too :eek1: :crazy:
 
The thud my truck made came from a loose body mount, the one just behnd the front fender.
It was especially loud on speed bumps and when turning right.
 
man, I love this forum. Everyone is helpful. To answer some questions, and I am about to go dive under my truck so might be able to have more in a bit.

Center pins on springs are fine, they are new.
Battery isn't loose, and sound is way heavier.
Body mounts are solid. I have checked them all.

I will check the bump stops and pull my swaybar off, that might have something to do with it.

Splines and yokes might be an issue, I have thought of that too but haven't been able to check it out yet.
 
It could be that sway bar. My sway bar bushings where worn out like yours, and it made the same popping niose.
 
the lip around my cat was close to the frame so when I went over bumps it would make heave bump sound
 
so I yanked my swaybar today. Couldn't even feel the difference when it was on. That boat anchor is staying off. Funny considering I spent hundreds of $'s on my GTI (VW) to add stiffer swaybars and strut tower tie bars etc and I am taking them off on my truck. :haha:

I think I found what the noise was. I had quickly checked my body mounts and assumed they were solid, but the front passenger side one was done. The bushing had worked its way out and the bolt was rattling around. I am sure that is the sound I have been hearing. I will be replacing all the body mounts and seeing if that fixes things. :doah:
 
Time for...

Oh-Oh..time for some new hockey pucks!.. :haha: ..

My 74 K20 had a "klunk"-"thud" noise once in a while when going over a dip in the road or turning sometimes..I thought at first it was my patched up floors and cab mounts( I used bumper jack bases for floor to frame bracket supports,between where the rubber biscuts go,instead of wimpy tiwan cab mount supports! ;) )--I later noticed all the bolts in the tranny crossmember to the frame were loose..tried tightening them,and they snapped off like nothing!--it did this several times..I attributed it to the fact someone before me cut off the upper arms on the crossmember that bolted to the top of the frame rail,and never put them back...

I eventually discovered the holes in the frame and crossmember were 1/2",and I was using 3/8" bolts!--that let things move around enough to stretch even grade 8 bolts out,and eventually shear them off..I put 1/2" bolts in instead,(also in the transfer case crossmember)--and it not only stopped the noise,the truck actually felt "stiffer" an less flexy going down the road!--they were still tight when I stripped and junked it earlier this year,they were in there for 4 years.. :crazy:
 
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