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Adjust or replace torsion bar in 1999 K1500?

lunytnz
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lunytnz Enthusiast

lunytnz

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My 1999 4-door Yukon 4x4 is bottoming out the front suspension on big dips in the road.  I replaced the shocks, but that wasn't enough to remedy the problem.

Since this model doesn't have springs, I'm wondering if I can adjust the torsion bars in the 1999 or if I need to replace them?  If I adjust the torsion bars, will it affect wheel alignment?

newdude Senior Enthusiast

newdude

Posted
Posted (edited)
55 minutes ago, lunytnz said:

My 1999 4-door Yukon 4x4 is bottoming out the front suspension on big dips in the road.  I replaced the shocks, but that wasn't enough to remedy the problem.

Since this model doesn't have springs, I'm wondering if I can adjust the torsion bars in the 1999 or if I need to replace them?  If I adjust the torsion bars, will it affect wheel alignment?

 

 

Are your jounce bumpers still there?  If they are, are they worn out or missing?  The jounce bumper is an integral part of the torsion bar IFS on these GMs.  

 

If they are original or the rubber is missing, GM discontinued the standard bumper which fit 1995-2000 Tahoe and was the same bumper 1999-2010 HD pickups.  Because of this though, you can use the 07-10 Z71 HD bumpers, p/n 15835667.  

 

We had a tech get burned by that on an 03 1 ton dump.  Front end was super bouncy, tech sold shocks, didn't fix it.  The jounce bumpers weren't even in the frame anymore, just the stud and nut that's molded into the bumper was left.  New bumpers and it drove great.  

Edited by newdude
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lunytnz Enthusiast

lunytnz

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Thanks for calling my attention to the jounce bumper!  I have the FSM, but I haven't been able to locate the bumper to make sure I'm looking at the right part. As far as I know, the bumper is original (I've owned it for over 20 years).

 

Here's a drawing from the service manual, as well as a picture of the front suspension in my rig. 

 

Can you point out the jounce bumper?  TIA!

 

20241025_162858.jpg

20241025_162029.jpg

newdude Senior Enthusiast

newdude

Posted
Posted
3 hours ago, lunytnz said:

Thanks for calling my attention to the jounce bumper!  I have the FSM, but I haven't been able to locate the bumper to make sure I'm looking at the right part. As far as I know, the bumper is original (I've owned it for over 20 years).

 

Here's a drawing from the service manual, as well as a picture of the front suspension in my rig. 

 

Can you point out the jounce bumper?  TIA!

 

20241025_162858.jpg

20241025_162029.jpg

 

 

 

It would be above the lower control arm, rear "A" of the lower arm mounted on the frame.  

 

 

 

jounce.thumb.png.b7131ad106c23fc9701dbddff66c6fcd.png

lunytnz Enthusiast

lunytnz

Posted
  • Author
Posted (edited)

Thx for the picture. Before I saw it, I took this picture from the other side. Is this where the bumper should be?

 

I presume the torsion bar is adjustable. Is that something I should look into, as well?

20241027_093852.thumb.jpg.667689d556685c8fcac377e9cf00500c.jpg

Edited by lunytnz
asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted

Yep, there should be a bumper there.

 

Torsion bars aren't typically 'adjusted'. But the years and mileage on the rig may have caused them to settle/wear some. There is a specification for adjustment - 'z-height'. It's not a very intuitive measurement to take. The easiest method, is to measure from the bottom of the lower control arm bolt to the ground and record the measurement. Measure from the rear lower control arm mounting bolt to the ground and record the measurement. The difference between these two is the 'z-height'. Refer to your factory service manual and confirm my measurement points because I might be remembering them wrong. It should also specify the measurement.

 

Torsion bar adjustment will require an alignment afterwards. 

  • 10 months later...
lunytnz Enthusiast

lunytnz

Posted
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Posted

Thanks, again, for pointing out the missing rubber bumper and helping to clarify where it was supposed to be!

 

I was able to find replacement parts at Napa (I was surprised that they are about the size of your fist).  It was difficult to get the nut off the old, rusty bolt, because the OE bumper was COMPLETELY disintegrated, but I eventually prevailed.

 

I put it to the test on a drive on a Forest Service road with big dips in the road and no problems with bottoming out the front suspension anymore.

 

Here's a picture of the front suspension with the new rubber bumper installed.

 

Cheers!

 

Yukon Suspension Bumper - replaced - Mar 2025.jpg

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