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Username Post: Uphill Clunk?        (Topic#347282)
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
09-22-17 01:15 PM - Post#2708534    

I have a 1990 K2500 I think it is called a light duty with the 6 lug wheels.
I have this really odd clunk I get when going uphill at any speed 25-60 it is only on a 18 degree grade or more hill, it will random clunk 1 or 2 times. I can not get it to clunk if I floor it on flat ground or even on a lower grade hill, It is only on the 18*+ hills without a load.
I think it started to happen after I got a few loads of gravel not sure if it is related or not.
I replaced the U joints and no change.
Looked all over and couldn't see anything out of place. it sounds like if i were to imagine someone dropping an engine block in my truck bed from a few feet up, I'm sure it is just the bed metal and the bed itself making it sound louder, but wow it is loud and i have turned heads on the road from it.
Any help where to look for a problem would be great, thanks.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
09-22-17 05:20 PM - Post#2708560    
    In response to TodMet

I forgot to mention, I did grease the yoke when I changed out the U joints.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
09-23-17 07:02 PM - Post#2708657    
    In response to TodMet

When the clunk happens do you feel anything in the vehicle? (Such as through the steering wheel, floor, brakes, etc...)

How about changes in the handling when it happens? (Loss of power, pulls to one side, etc...)

-91 Sierra C2500, now K2500
-81 Chev K20


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
09-24-17 04:14 PM - Post#2708712    
    In response to stumppuller

I didn't get a chance till today to check if other things happen and could feel it. I tried 2 times today going up the hill out front and I couldn't get it to do it at all, I really doubt it would just go away. I don't like the idea of me possibly hurting it more if it is a problem so I do not like to go up the hills if I do not have to. but from memory I think it just made the clunk and maybe jerked a little, I do not recall anything other then that.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


Edited by TodMet on 09-24-17 04:16 PM. Reason for edit: No reason given.

 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
09-24-17 06:00 PM - Post#2708724    
    In response to TodMet

Since it may have started after hauling some heavy loads, I'd be checking;

- The leaf springs for cracks and broken eye's
- Rear Shackles
- U bolts (these can rust badly and fail in the lower saddle mount assembly)
- Shock mounts upper and lower.
- Bed mounts
- Frame and all suspension brackets/supports for any damage

Does the truck have much rust or get exposed to a lot of salt?

-91 Sierra C2500, now K2500
-81 Chev K20


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
09-24-17 06:14 PM - Post#2708727    
    In response to stumppuller

Just your normal amount of surface rust you would expect living in Seattle area around the sound.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
09-24-17 06:39 PM - Post#2708730    
    In response to TodMet

Good. The u-bolts are still a concern though. They fill with crud, then rot the bolt until it snaps. It is difficult to see until they are removed - Then you will be stunned at how little was still holding it all together.

Try lifting the rear high, put some jackstands under the frame, and lower the axle to let the rear suspension droop. This may help make any problems more apparent as the springs are under much less tension.

-91 Sierra C2500, now K2500
-81 Chev K20


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
09-25-17 05:12 PM - Post#2708838    
    In response to stumppuller

Thanks, will check it out as soon as this flu passes.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
10-09-17 07:34 PM - Post#2710342    
    In response to stumppuller

I got a chance to look at it today and didn't see anything with it up. odd thing also is I can not get it to clunk now. I don't think it could fix itself.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
10-10-17 09:57 PM - Post#2710468    
    In response to TodMet

That's odd. If it suddenly stopped doing it after lifting and lowering the truck, I would suspect there is possibly an issue somewhere in the suspension.

Maybe look for and signs that something is striking the bottom of the bed (scuffs, undercoat scraped off). Just throwing out ideas here....

-91 Sierra C2500, now K2500
-81 Chev K20


 
scrambldcj8 
Senior Member
Posts: 2357
scrambldcj8
Loc: MA
Reg: 04-06-03
10-14-17 04:41 AM - Post#2710806    
    In response to stumppuller

maybe already mentioned but....after a load of gravel? >>> broken spring (I'd say low probability on that one but possible). But maybe something like a binding spring clamp or with the age of the truck a rotted out leaf spring bushing (spring eye) or a binding leaf spring shackle.

What I am trying to focus on would be anything related to weight transfer or weight shift to the rear...such as climbing only 18+ grades as you say. This is an interesting one for sure....



 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
12-27-17 01:00 AM - Post#2719079    
    In response to stumppuller

Clunk came back.
Today I really spent time looking it over for a few hours and didn't see anything really.
It happens now on almost all inclines, not all the time though, it is very random. I think I can feel it a bit like jerking back ever so slightly.
I looked at the U bolts but did not remove them, I think if I removed them I would just want to have new ones to replace them, but they did seem solid to the eye.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
Shepherd 
Frequent Contributor
Posts: 1418

Loc: Lake George, NY
Reg: 11-11-15
12-27-17 04:49 AM - Post#2719081    
    In response to TodMet

If you have torsion bar front suspension, check the torsion bar mounts to the frame, common failure point.



 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
12-27-17 12:54 PM - Post#2719119    
    In response to Shepherd

I checked it and it looks good, in fact looks to have been replaced with a new one and mounting bolts are tight and in place, no rust or damage to mounting area. These were the type with factory rivets there and had to be drilled/cut out and replaced with bolts I have now there correct?
It seems like the mounting area would make a clunk over bumps or turning and my clunk happens on smooth inclines. it sounds to be more in the rear also.
Thanks for the input.

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
12-27-17 10:31 PM - Post#2719178    
    In response to TodMet

The torsion bar bracket was bolted from the factory (at least as for as I know). I've never seen rivets holding it on.

Have you taken a good look at the front suspension? I know it sounds and feels like the rear is the issue, but sometimes the noises/clunks can be misleading.

Make sure to lift the control arm a bit with a jack when checking for play. This unloads the considerable force pushing down on the front a arms when the truck is on jack-stands. Without doing this, it will be difficult to find any loose joints, bushings, etc.

How's the gas tank straps? Cab mounts? Bed mounts?

-91 Sierra C2500, now K2500
-81 Chev K20


 
TodMet 
Poster
Posts: 73
TodMet
Age: 50
Loc: Port Orchard
Reg: 09-22-16
12-29-17 12:18 AM - Post#2719289    
    In response to stumppuller

Took a good look tonight at the front end and it looked like someone has gone thru it not that long ago, it is nice looking couldn't find anything. Only part that didn't look newish from the middle to the front was the trans mount, but didn't see any indication of it rubbing anything.
I think I will take out the leaf springs and check out the U-Bolts better and buy new ones. I told my brother this and he had a box of Energy Suspension 3.2128R Rear Leaf Spring Bushing Set in his garage from a storage unit he bought a bit ago, sometimes I love my hoarder brother for that, so I will just put new bushings in while I am there. Will not hurt and it is free so...

Tod
1990 K2500 Chevy Cheyenne 5.7 TBI
1978 Chevy Camaro Z28 5.7
1975 Chevy Monza Towne Coupe 5.7


 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 827
stumppuller
Loc: Canada
Reg: 11-01-04
12-29-17 11:05 PM - Post#2719393    
    In response to TodMet

If you are going to pull the spring packs apart you'll need replacement center pins. The originals often fail during removal.

Also, you might want to consider flipping the U bolts. No need to buy expensive kits, any Chevy or Ford with the same spring pack width will have the plates. The originals are often pretty bad once they are removed. Here's a good explanation with pictures;

http://www.offroaddesign.com/catalog/uboltreversal ...

-91 Sierra C2500, now K2500
-81 Chev K20


 
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