Sagging front end 2004 Z71

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Donal

Full Access Member
Joined
Mar 30, 2021
Posts
200
Reaction score
286
Location
Americus Georgia
While I am thinking about it. The torsion bars are springs that provide the spring in suspension. Some vehicles use coiled bars steel to provide the spring. All steel have the same modulus of elasticity, some just go into plasitc deformation at lower loads. So, if you measure the length of the torsion bars you see that are about 48 inches in length. If you go to some off brand of vehicle of similar size, you may see the coiled springs and the coils are about 8 inches across. If you leasure the around one coil you will see the llength of the coil is about 25 inches. Both of the springs, bar and coils are loaded in torsion or twisting load when inservice in the vehicle. So one vehicle the suspension height is provided one bar of steel about 48 inches and the other is provided by a bar of steel many times longer, number of coils times the length of each coil. So the Tahoe ride height is provide by a bar loaded in the elastic range. Along comes someone that wants to change the ride height of the vehicle by incresing the load on the torsion bar. Well, small adjustments are made and all is good. Sso let change the ride height even more and we dont have time to jack up the vehicle to unload the bars. We gonna getter done. Soon the bar load is sufficient to take the bar operating load to the plastic range, never to return to the original dimension. So here and now, we have a new owner that thinks wow what beautiful Tahoe. But why does it sag and why does it steer funny and why does the tires wear funny and why do the tires go in at the top when I back up, etc. O the moral. If you want to raise or lower vehicle get the components to make the change. If you need to convert to the coil over option. Go
 

BlueBurb04

TYF Newbie
Joined
Dec 8, 2022
Posts
1
Reaction score
0
I'm having the same issue on my 04 Suburban (hope it's ok to post here with a Suburban). Drivers side bar sags. Even with lift keys. I can barely get it airspace between the lower arm and bump stop. And that's with junk yard Z71 bars. (Mine is not a Z71 Called the parts guy at the dealer we use, looking for 04 Suburban Z71 bars (Z71 bars have a much higher torque rating), there is one passenger side left in the country, and the drivers side is discontinued. Ugh. With how popular these trucks are, it makes no sense that the aftermarket doesn't make replacement torsion bars!
 

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,229
Reaction score
31,639
Location
Willamette Valley
I'm having the same issue on my 04 Suburban (hope it's ok to post here with a Suburban). Drivers side bar sags. Even with lift keys. I can barely get it airspace between the lower arm and bump stop. And that's with junk yard Z71 bars. (Mine is not a Z71 Called the parts guy at the dealer we use, looking for 04 Suburban Z71 bars (Z71 bars have a much higher torque rating), there is one passenger side left in the country, and the drivers side is discontinued. Ugh. With how popular these trucks are, it makes no sense that the aftermarket doesn't make replacement torsion bars!
Maybe this will help

 

Fless

Staff member
Super Moderator
Joined
Apr 2, 2017
Posts
10,454
Reaction score
20,754
Location
Elev 5,280
I'm having the same issue on my 04 Suburban (hope it's ok to post here with a Suburban). Drivers side bar sags. Even with lift keys. I can barely get it airspace between the lower arm and bump stop. And that's with junk yard Z71 bars. (Mine is not a Z71 Called the parts guy at the dealer we use, looking for 04 Suburban Z71 bars (Z71 bars have a much higher torque rating), there is one passenger side left in the country, and the drivers side is discontinued. Ugh. With how popular these trucks are, it makes no sense that the aftermarket doesn't make replacement torsion bars!

You shouldn't have any space between the lower control arm and the jounce (not "bump") stops. See this link for more detail:

 

Alex_M

Full Access Member
Joined
Sep 27, 2021
Posts
357
Reaction score
655
The drivers side lean is super common on a wide range of vehicles at a certain age, and very well documented particularly on full size trucks. This generation Tahoe/Suburban/Silverado has been starting to enter that age in the last few years. The drivers side sag is because of the additional weight carried on the drivers side, ie. the driver and the gas tank.

I have seen many creative solutions. Some folks swap springs side to side, some folks add helper leaves (in leaf sprung vehicles) to the sagging side, some just crank up the drivers side torsion bar (in vehicles with torsion bars like our Tahoe's). For me, the low buck option is to swap the rear springs side to side and crank the drivers torsion bar up. The "correct" repair would be to install all new springs front and rear, but realistically the cost outweighs the benefit on most vehicles of this age, except for some enthusiasts.

For an extreme case, which yours (OPs) sounds like, I would look into getting a set of torsion bars out of the junk yard. Make note of which is driver, which is passenger if they are not marked.

Now, this piece is important. Some, not all, but some GMs of this generation have torsion bars that are factory marked left and right (from the drivers perspective). These are easy to tell because they have an L and an R cast into the end. You cannot swap them side to side. The truck will either set on the bump stops, or it will be almost impossible to get the torsion key installed and once you manage to there will be so much preload (even at the lowest setting) that the suspension will be at full droop/max height all the time.

In my experience if they are not marked left to right then they are the heavier spring rate torsion bars. If you use these the ride will be a bit rougher and a fair bit taller as well. I cannot remember the numbers off hand, but both sets have numbers cast into them. This *may* have been a Z71 option, it *may* have been a factory plow package, or it's even possible that I have unknowingly parted out a half ton truck that someone put 2500 torsion bars in. The last I think is unlikely. If it were me, I would look for a set that were standard marked left and right, and use the lift keys you have.

One other note for others who may find this since I brought up 2500 torsion bars, 2500 stock torsion keys actually lower a half ton truck and vice versa.
 

Forum statistics

Threads
129,170
Posts
1,811,531
Members
92,258
Latest member
bcupp4086
Top