Zr2 front suspension

revrnd · April 29, 2025

On 4/6/2025 at 9:10 PM, Chuck FB said:

On my truck I bought recently I discovered that the left side was a 1/2 inch higher than the right side and yes the fuel tank was full and not really anything else in the truck. That really showed up on the key bolts as the right hand bolt was sticking out quite a bit more, GM seems to do a rather poor adjustment at the factory for the ride height I have found, the trucks are not consistent off the assembly line.

I hear you when we were building GMT400s there was a checking fixture for the Z height. One of my jobs was validating the spare fixture & then exchanging & validating the fixture that had been in use. This was done @ the start of each shift, days & nights.

Fast forward to 1997 when I transferred back to the Truck Plant. This was near the end of the GMT800 run. Imagine my surprise when I was out along the 'flat top' conveyor & saw no fixture in use. Same thing during GMT900 production.

I have no idea how the Z height has been set since.

Edited April 30, 2025 by revrnd

Chuck FB · April 29, 2025

9 minutes ago, revrnd said:

I hear you when we were building GMT400s there was a checking fixture for the Z height. One of my jobs was validating the spare picture & then exchanging & validating the fixture that had been in use. This was done @ the start of each shift, days & nights.

Fast forward to 1997 when I transferred back to the Truck Plant. This was near the end of the GMT800 run. Imagine my surprise when I was out along the 'flat top' conveyor & saw no fixture in use. Same thing during GMT900 production.

I have no idea how the Z height has been set since.

That's interesting and I certainly don't know either, would it be some sort of scanner that is the "eyeball" or in fact the person who wears thick inserts in their shoes but forgot to put one of them in the day my truck was build !. See what happened when you were dragged off in a different direction and were not there to hold the hand of the person who should have known better but it wasn't that persons job to care. I didn't even need to pick up a measuring tape to realize something was off by laying under the truck, that gap difference between the left and right jounce bumpers on the lower control arm and how it just happened to correspond to the right hand key bolt sticking out substantially further than the left one. Its not something that all truck buyers of a GM product with torsion bars would even have on the radar and drive it like that for years and even alignment shops from what I have seen are not really paying much attention to that as their job is to align the wheels and make money for the shop by throwing front end parts at the vehicle or just get the alignment done quick and out the door for the base fee charged.

revrnd · April 30, 2025

I should drop by the 1 alignment shop that I've dealt w/ in the past. Ask them what the situation is w/ the GM pick ups & their torsion bar adjustment.

@newdude What is the PN for the transfer case skidplate bolts?

newdude · April 30, 2025

15 minutes ago, revrnd said:

I should drop by the 1 alignment shop that I've dealt w/ in the past. Ask them what the situation is w/ the GM pick ups & their torsion bar adjustment.

@newdude What is the PN for the transfer case skidplate bolts?

I can find out.

Z height is still a deal for aligning the torsion bar IFS on HD.

kylant · May 7, 2025

all of my parts are ordered. waiting on a few to come in. I ended up doing all factory parts with Fox HTO shocks, Cognito comfort ride torsion bars and rear mini-leaf packs.

I was bored and installed the rear mini-packs and torsion bars. I used 1 spacer of the 2 on the leafs and the truck gained 1.5" rear lift. for the torsion bars, I had to crank the keys 4 full turns in order to have the same stock ride height.
The ride is better, but not 1/2 ton better. I was expecting a bit more.

hopefully the rest of the front swap parts will be in soon

Chuck FB · May 8, 2025

11 hours ago, kylant said:

all of my parts are ordered. waiting on a few to come in. I ended up doing all factory parts with Fox HTO shocks, Cognito comfort ride torsion bars and rear mini-leaf packs.

I was bored and installed the rear mini-packs and torsion bars. I used 1 spacer of the 2 on the leafs and the truck gained 1.5" rear lift. for the torsion bars, I had to crank the keys 4 full turns in order to have the same stock ride height.
The ride is better, but not 1/2 ton better. I was expecting a bit more.

hopefully the rest of the front swap parts will be in soon

What rating did the bars have that you took out ?

Once you get it all set up and whatever tires you will run, then you can dig into what tire pressures your able to run based on your axle weights. Maybe you've already done that but if not and the tire pressures are being run on the high side, that can take the edge off of the small bump harshness, cracks in the pavement etc.

kylant · May 8, 2025

3 hours ago, Chuck FB said:

What rating did the bars have that you took out ?

Once you get it all set up and whatever tires you will run, then you can dig into what tire pressures your able to run based on your axle weights. Maybe you've already done that but if not and the tire pressures are being run on the high side, that can take the edge off of the small bump harshness, cracks in the pavement etc.

They are 5600 bars.

I am currently running the stock 275/65-20 tires at 50/45.
better shocks and tires with more air volume/sidewall will improve the ride too.

Chuck FB · May 8, 2025

3 hours ago, kylant said:

They are 5600 bars.

I am currently running the stock 275/65-20 tires at 50/45.
better shocks and tires with more air volume/sidewall will improve the ride too.

Oh, your truck is a diesel I gather with that factory bar rating, that should make quite a difference to the front end ride with the much lighter bar and no doubt some of that will equate with what the ride height gets set to as well. Your not done with the whole setup either and as to the rear suspension, I haven't a clue what that setup performs like compared to completely stock. As to the factory size tire pressures, 50 front for the diesel seems to be the low limit due to the weight ( I can squeak by with 40 with the gas ), the rear comes down to what is or will be in it or if towing and if very little in the rear can drop down to 35 with the factory tires.

Do you already know what tire size your going with and if it will be metric size or a standard inch sized tire ?

Epsilon Plus · May 8, 2025

What's the chances Cognitos comfort bars are just GM 4400# off the shelf $500/pair bars marked up almost double?

Do we really think they are pouring steel to make their own bars?

Interesting that they don't advertise the rate anywhere...

I remember seeing somewhere they advertise 21% less stiff. Well since most people are programmed to automatically think diesel with HD trucks, and the most common HD truck is a CCSB 4x4, if you take the 5600# rate of a diesel CCSB 4x4 and subtract 21% you just happen to get 4424.

I'm pretty sure their $900 bars are just part numbers 84745473 & 84745475 that are $454.18 on GM Parts Direct (pre shipping). $549.50 to your dealer from main GM after their 20% off 400+ they have right now.

Edited May 8, 2025 by Epsilon Plus

kylant · May 8, 2025

52 minutes ago, Epsilon Plus said:

What's the chances Cognitos comfort bars are just GM 4400# off the shelf $500/pair bars marked up almost double?

Do we really think they are pouring steel to make their own bars?

Interesting that they don't advertise the rate anywhere...

I remember seeing somewhere they advertise 21% less stiff. Well since most people are programmed to automatically think diesel with HD trucks, and the most common HD truck is a CCSB 4x4, if you take the 5600# rate of a diesel CCSB 4x4 and subtract 21% you just happen to get 4424.

I'm pretty sure their $900 bars are just part numbers 84745473 & 84745475 that are $454.18 on GM Parts Direct (pre shipping). $549.50 to your dealer from main GM after their 20% off 400+ they have right now.

they are 100% GM bars. It's just a matter of figuring out which ones. I called Cognito and they said they were "700 pound" rated. I told them that didn't make any sense but that's what the lady told me.

Edited May 8, 2025 by kylant

Chuck FB · May 8, 2025

47 minutes ago, Epsilon Plus said:

What's the chances Cognitos comfort bars are just GM 4400# off the shelf $500/pair bars marked up almost double?

Do we really think they are pouring steel to make their own bars?

Interesting that they don't advertise the rate anywhere...

I remember seeing somewhere they advertise 21% less stiff. Well since most people are programmed to automatically think diesel with HD trucks, and the most common HD truck is a CCSB 4x4, if you take the 5600# rate of a diesel CCSB 4x4 and subtract 21% you just happen to get 4424.

I'm pretty sure their $900 bars are just part numbers 84745473 & 84745475 that are $454.18 on GM Parts Direct (pre shipping). $549.50 to your dealer from main GM after their 20% off 400+ they have right now.

I've wondered this all along as well, not sure if GM outsources that part but if they did and was not a patented item, the producer of the part could easily sell to someone else. Or if its actually made by a GM tied plant, then buy them in bulk for a good price and mark the crap out of their resale price. Any markings on the bars could be compared and that diameter to see how closely it matches up with a set of 4400 lb GM bars. I just have this funny feeling there is a reason why the info from Cognito is so vague, and yes 21% less stiff compared to what GM bars without saying which GM bars they are even comparing to.

GMCnewbie · May 8, 2025

I'm not saying they aren't GM bars, but the markings on the bars are not the same between the stock 4800 bars and the Cognito bars that I installed on my truck. Im also interested in finding out the actual ratings on these bars. My front end has noticeably smoother ride now.

Epsilon Plus · May 8, 2025

I don't know that I would want anything less than 4400 anyway, maybe 4000?

I have 4800 right now since I'm gas. Dunno if a 400# drop on each bar is going to feel that much different for half a thousand dollars. I might go that route though if I ditch these overly stiff Bilstein 5100s.

GMCnewbie · May 8, 2025

I went with the new Fox 2.5 HTO shocks along with the Cognito torsion bars on my gasser. The ride is so much better now when hitting speed bumps or anything else in the roads. I've never used the Bilstein 5100's. I've heard their fairly stiff which is why I didn't go with them this time around. I had the 4600's on a pair of Rams from the factory and hated them on both trucks. I wasn't a fan of the Fox 2.0 shocks, but they greatly improved ride quality over the 4600's on my old Power Wagon.

kylant · May 8, 2025

the markings on the front ends of the cognito bars are identical to the factory markings. this leads me to believe they are indeed gm. i am convinced they are just a lighter rate factory bars