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2021 Denali HD Fabtech Lift and 37s
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I have been considering these for my 21......
 

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When you swap the old torsion bars out, is it as simple as removing the torsion key and then the old torsion bars can be negotiated out? Or is there all kinds of other disassembly required in the front of the truck, or crossmembers etc? Looking under the truck it appears I could push the bar forward, then back out once the key is removed, no? And just install new ones with reverse procedure?
 

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Just need to drop cross member that bars run through, the bars are directional and side specific
Thanks! I see what you mean. The cross member that holds the keys. Looks like two bolts ( be tight getting a wrench in there) but take that out after the keys are removed and torsion bars can be finagled out. Ok! Would you say definitely doable for a guy with mid level skills? No special tools required except maybe a huge C clamp to de-tension the keys?
 

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So I actually ended up getting a set of 2020 Silverado 2500 torsion bars on ebay. These are the stock bars that would have been in my AT4 had I not bought one with the snowplow package. Measuring the diameters and calculating volume they had 7 or 8% less volume than the snowplow bars. I installed them, (super easy) and the ride is notably better. However, what I'm learning is that the relationship between the jouncers and the control arms are VERY important. Interestingly also, there are 4 jouncers on the front end of the truck. I'll call them extreme forward and middle forward, not to be confused with the rear jouncers above the leaf springs. The extreme forward and middle forward jouncers do not meet the control arm at the same time. In other words as you lower the rake of the truck the middle forwards will touch the control arm before the extreme forwards. I"m guess there is maybe 1/8 to 3/16 of an inch difference in when they touch the control arm. I have found through experimentation that squishing the middle forward jouncer just a little to allow the extreme forward jouncer to just kiss the control arm results in my best ride so far. If I raise it up from there where the middle forward jouncer kisses, and the extreme forward jouncer is about 1/8 inch above control arm, this has a noticeably worse ride. Obviously the higher the rake from there the worse the ride gets. ( I do drive the truck aggressively over bumps after every adjustment before I even check measurements or jouncer positions)

As far as tire pressure: I reached out to Goodyear and received the documents to account for different psi allowable under different loads. I'm assuming my truck carries 60% of its weight on the front wheels and 40% on the back. Assumption is based on multiple weight reports that show a 57/43 % split, albeit on older duramax trucks. And just for daily driving (not towing or hauling) a very comfortable figure of 9500 gross weight (full gas tank, myself, wife, and two kids, and 400 lbs of whatever else I put in the truck) allows me to go down to 55psi in the front and 40psi in the back. I've got 56 in the front and 46 in the back right now. Interestingly I had 56 in front and 50 in back and the ride seemed better than when I dropped the rears to 46. I'll continue experimenting there, but at least I know I'm 100% safe running those lower pressures now that I have the tire docs. Just can't forget to inflate before I haul. And I won't.

If anyone has any thoughts or concerns for me that don't include "why would you buy a HD truck and then bitch about the ride" I'd love to hear them. By the way, I've improved the ride already without compromising the handling or towing capacity or payload. From what I can tell so far using the stock non-snowplow torsion bars reduced my forward axel allowable weight from 6600 to 6000 but this has zero implication for towing or hauling at the levels I will be using it for.

If I still cannot get satisfied my next step will be upgrading the Rancho shocks, moving to an 18 inch wheel vs the 20 I have. Because I test drove a SLT 2500 non-snowplow with 18 inch wheels and it felt so much better than my AT4. But it didn't look as cool Lol.
 

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Great info keep me posted.
I'm currently in a 3500 at4 with standard tortion bars and factory pressure. Got about 3000kms on it now so thinking about starting to make some adjustments to see if I can get the ride more comfortable if possible. I ordered 18" wheels but that truck isn't coming so the truck I ended up with has the 20s...my assumption was that the more sidewall the softer the ride would be.
 

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Did you have to get the tpms programming changed to be able to run 55F/40R without getting warnings?

I had my 'recommended' changed to 50F/50R. Usually ran cold pressures in the 55F/52R range. Had the programming done at new so didn't run it with reduced pressures before changing the tpms settings.

(after the programming was changed, the 'recommended' pressures in the GM phone app displayed the newly programmed numbers)
 

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Did you have to get the tpms programming changed to be able to run 55F/40R without getting warnings?

I had my 'recommended' changed to 50F/50R. Usually ran cold pressures in the 55F/52R range. Had the programming done at new so didn't run it with reduced pressures before changing the tpms settings.

(after the programming was changed, the 'recommended' pressures in the GM phone app displayed the newly programmed numbers)
Is there a way I can change the tpms programming or does that need to be done at the dealer?
 

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Is there a way I can change the tpms programming or does that need to be done at the dealer?
Dealer laptop was used for mine (wirelessly, fwiw)

I'm not aware of any other way to change it.

Also requires one of the 'teach tools' to re-learn the tire locations when tires are rotated.
The old method of letting out air no longer works.
 

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Great info keep me posted.
I'm currently in a 3500 at4 with standard tortion bars and factory pressure. Got about 3000kms on it now so thinking about starting to make some adjustments to see if I can get the ride more comfortable if possible. I ordered 18" wheels but that truck isn't coming so the truck I ended up with has the 20s...my assumption was that the more sidewall the softer the ride would be.
I'd be very interested to know what your factory rake is? Are your extreme front jouncers just kissing the control arm. The best way to know that is reach under there and try to move them with your fingers. If you hear a squeak, they're barely touching. If they wiggle but no sound they are not touching. If they don't wiggle, they're tight against the control arm.

The reason I ask is because I'm at a loss to know what the factory setting is. Mine came all jacked up with one side of my truck a full 1.5 inches higher than the other, and one of the torsion key bolt ran way in and the other way out. I called the dealership and they acted clueless.
 

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Did you have to get the tpms programming changed to be able to run 55F/40R without getting warnings?

I had my 'recommended' changed to 50F/50R. Usually ran cold pressures in the 55F/52R range. Had the programming done at new so didn't run it with reduced pressures before changing the tpms settings.

(after the programming was changed, the 'recommended' pressures in the GM phone app displayed the newly programmed numbers)
Good to know. No I haven't reprogrammed yet. I'm just dealing with the warnings on the display, and I texted STOP to the text messages Lol.
 

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I'd be very interested to know what your factory rake is? Are your extreme front jouncers just kissing the control arm. The best way to know that is reach under there and try to move them with your fingers. If you hear a squeak, they're barely touching. If they wiggle but no sound they are not touching. If they don't wiggle, they're tight against the control arm.

The reason I ask is because I'm at a loss to know what the factory setting is. Mine came all jacked up with one side of my truck a full 1.5 inches higher than the other, and one of the torsion key bolt ran way in and the other way out. I called the dealership and they acted clueless.
I will try and get under there this week and see what I can see. You are thinking unloaded on a flat surface yes?
 
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