How to lower your GMT-800 torsion bar sprung truck cheaply.

[Bigredmariner]

So my truck is a 2006 Chevrolet Silverado Z71 4WD. I wanted to lower the thing but not spend a bunch of money on it. This lead me to two things. 1: De-cranking the torsion bars. 2: Removing the 2 inch blocks from the rear end.
I ordered 2WD U-bolts for the project from gmpartsdirect.com, pn-15002781, I ordered 4 and that cost me $63 with taxes and shipping.

I took measurements at all 4 corners and the truck was sitting at 36". This was measured from the ground to the center of the fender well. With the front of the truck jacked up I unscrewed the torsion bar adjusting screws 8 turns. Removed the rubber bump stops and cut about 3/4" off of them. I set the truck back on the ground and measured 34" in the front. The CV axles are parallel and I don't think they will be an issue.

The rear was a little harder. Jack up the rear of the truck and place jack stands under the frame. Let the frame rest on the stands and make sure you have it high enough for the rearend to drop for the block removal.
Place the jack under the rear end supporting it while you remove the U-bolts.

With the U-bolts removed, lower the rear end down enough to get the blocks out.

Here's the difference between the 4WD U-bolts and the 2WD version.

Remove the blocks and wipe down all mating surfaces. Jack rear end back up into place and install new U-bolts. Tighten evenly and set truck back on the ground. Mine measured 34" at the rear which gave me a level stance all the way around. New shocks are next and I am thinking about replacing the 4wd bump stops with 2WD bump stops. I will be getting the truck realigned after my tires and wheels arrive.

Here's the final stance.

 

[Cashezo]

Excellent write up! Truck looks very good, man!

 

[drperry]

Nice!

This works for any GM IFS 4x4 truck

The only difference in the S-Series, is that I actually have to ADD blocks to lower mine... Since my springs are under the axle

 

[OldCracker29]

Nice write up Jarrod, but wouldn't it have been easier to just let the air out of the tires? That would've lowered it.

 

[Matt_]

Looks good.

The only thing I would've done differently is taken a little less off the compression stop. They are designed to work with the suspension on these trucks and should actually contact the LCA during normal driving (they're meant to compress, not stop motion).

Since they also do control the upper limit of suspension travel, I would just make sure that your shocks are not the "new" limit for compression.

So just an additional step that I would do is:
Unbolt bottom of shock
Remove compression stop
Completely unscrew torsion bar adjustment bolt to drop front end as far as possible.
Fully compress shock.

A) If shock needs to be extended to connect to LCA, take measurement between LCA and compression stop mount. Cut compression stop on an angle so that a "flat" section rests about 1/8" to 1/2" above the LCA (this is a standard distance.. i would opt for the 1/8" side... you can always take more off, and 1/2" may be too much for a "lowered" setup)

B) If fully compressed shock isn't long enough to conntec to LCA, Jack truck up from crossmember until shock needs to extend 1/2" beyond fully compressed state to align mounting hole. Then take compression stop measurement and cut per instructions in 'A'.

​

Note that I've never lowered a vehicle using this method... so obviously those instructions may not be 100% realistic. But they portray the general idea that im talking about;; basically find the suspension compression limiting factor.

The way I see it, if someone posted a thread showing "how to" install a leveling kit and one of the steps they took was to cut off the droop stops that limit UCA down travel, a lot of people would be saying "oooooh that's a bad idea". Same principle applies here, you dont want your shock topping out or your balljoints getting torqued with too much upwards travel.

 

[Bigredmariner]

Looks good.

The only thing I would've done differently is taken a little less off the compression stop. They are designed to work with the suspension on these trucks and should actually contact the LCA during normal driving (they're meant to compress, not stop motion).

Since they also do control the upper limit of suspension travel, I would just make sure that your shocks are not the "new" limit for compression.

So just an additional step that I would do is:
Unbolt bottom of shock
Remove compression stop
Completely unscrew torsion bar adjustment bolt to drop front end as far as possible.
Fully compress shock.

A) If shock needs to be extended to connect to LCA, take measurement between LCA and compression stop mount. Cut compression stop on an angle so that a "flat" section rests about 1/8" to 1/2" above the LCA (this is a standard distance.. i would opt for the 1/8" side... you can always take more off, and 1/2" may be too much for a "lowered" setup)

B) If fully compressed shock isn't long enough to conntec to LCA, Jack truck up from crossmember until shock needs to extend 1/2" beyond fully compressed state to align mounting hole. Then take compression stop measurement and cut per instructions in 'A'.

​

Note that I've never lowered a vehicle using this method... so obviously those instructions may not be 100% realistic. But they portray the general idea that im talking about;; basically find the suspension compression limiting factor.

The way I see it, if someone posted a thread showing "how to" install a leveling kit and one of the steps they took was to cut off the droop stops that limit UCA down travel, a lot of people would be saying "oooooh that's a bad idea". Same principle applies here, you dont want your shock topping out or your balljoints getting torqued with too much upwards travel.

I'll give that a try, I finally found the part numbers for the 2WD bump stops and will order them probably this afternoon. When I put them in I will do the checks you suggested and see where I'm at. Correct shocks are another thing on the to do list. Thanks for the info.

 

[Zembonez]

Lookin good J-rod. The wheels and tires are going to make a HUGE difference too! I do agree with Matt on the front bump stops. You may have some real crashing bottom outs over big stuff with that much chopped.

 

[Matt_]

No problem man.

Also, the 2wd GMT800s have different LCAs... the bump stop may be in a different location and may not work exactly the way you want it to (the length may not be a 1:1 for the ride height change). Not 100% sure though, maybe someone with a 2wd can throw up a picture.

 

[Bigredmariner]

They are cheap enough so I may order them anyway and also get 2 new 4WD bumps to replace the ones I hacked up.

 

[Zembonez]

Thanks for another great write up Jarrod. Feel free to clean up your HOW TO threads once we all get through yappin.