Hey all, just got done replacing front lower control arms in my 05 Z71. I actually just replaced them with stock replacement Moog pieces as I've been chasing a clunk. As soon as I got the front control arms out of the truck, I knew they weren't the culprit. Bushings were intact (even though they didn't look like it on the truck) and balljoints did not have any unusual play. I can't feel the clunk in the brake pedal or floorboard, but I can feel through the steering column. After additional research, I think it's the sector shaft, oh well my stock control arms had 140k on them. Anyways, in order to remove the front control arms, I had to back off the torsion bar keys to full loose. I left them that way when I put it all back together. For the rear, I removed the block and used Belltech 1-2" shackles in the bottom most position (I think that's 1" lowering). I also installed Bilstein HD shocks all around (4600 series).

My before ride heights were:

FL 35.5" FR 35.5"
RL 38.25" RR 38.5"

New ride heights:
FL 33.5" FR 33.5"
RL 35.5" RR 35.75"

I feel like the rear needs to come down to match the front, or the front needs to come up to match the rear. The front seems a bit bumpsteery, hard to explain. That, and I don't like the rake. Considering the rear blocks are 2", that means the shackles only lowered the truck an additional .75". Would the rear get a lot harsher if I put them in the upper shackle hole, and then raised the front up an inch to make things relatively level?

 

Use some 2-3" shackles if available. Put just enough preload on the torsion bars so the bolts don't fall out. This is how my and many other Duramax's are lowered.Also your front looks toed in which could cause your front end issues. I recommend an alignment once your ride height is where u want it.

 

My sig picture is 2" shackles and removed blocks in the rear and 2" keys up front turned all the way up (max lift). Ive got about a perfect 3/4" of rake. Ive also got the bilstein 4600s. Rides pretty nice even with my added rear sway bar and front end riding hard on the bumpstops.

 

I have the 1-2" shackles and I'll put the spring on the 2" position. For the front, should I make sure the axles and tie rod ends are parallel or close to it?

Out of curiosity, are lowering spindles the "correct" way to lower the front?

 

Ok I installed the shackles on the upper most hole, ride height is a lot more level now. I also adjusted the torsion bars so there is just enough preload so bolts don't fall out. Rides pretty nice! Except the lower control arms are REAL close to the bumpstops (did trim them down quite a bit), and I think whenever I hit dips, they hit the control arms and unsettle the suspension. What's the solution for this? Spindles? Aftermarket control arms? I think I'll try trimming the bumpstops a bit more and more of an angle to match the control arm rotation. Any ideas guys?

 

Those are not bump stops. They are called jounce bumpers and a lot of trucks ride on them in stock form. As long as it isn't too harsh for your liking, it is fine that they are hitting. At least this is how it was on my Duramax. If I'm giving bad info someone correct me please.

 

Hmmm, ok. Would spindles or control arms make the ride better? I'm not 100% happy with the ride, feels kinda bumpsteery and harsh at the front. I don't want to go any lower at this point, just want to improve the ride.

 

This is an issue Im trying to figure out now as well. The front bumps are part of the suspension. They are what allows a progressive feel to it. I remember reading some good info a few years back on SilveradoSS dot com on what to do when lowering the front and keeping it from being to harsh.

 

Should I have not trimmed them at all? If they're supposed to ride on them, then I'm in trouble!

 

Trimming them is ok. The thread I just looked through says to either cut one nub at a time, or try drilling a few holes in them first. Factory bumpers are preferred as they are softer than the aftermarket ones. Im going to try doing this soon.