Project Report: Front Torsion Springs Remove and Replace

[Another JR]

Hi All,

 

I’ve mentioned in a few threads that I was planning to swap out the optional 5600 lbs FGAWR heavy duty camper springs and install the base 5200 lbs rated springs on my GMC 3500hd cclb srw gas truck. I just did the job this morning and wanted to report on it because it was actually quite easy. 
 

The parts (left and right torsion bars) totaled $570 with shipping and 10% WA sales tax from my local Chevy dealer. It was the same price as the on line dealers and the shipping pickup is more convenient. Plus I like them and want to give them business. My GMC dealer next door charges msrp for parts.  
 

The job took me 2.5 hours, but the first 20 minutes of that was figuring out how to properly jack and support it because it was the first time for me on that truck.  The torsion springs were not stuck at all to either the lower arm or the torsion key, and once they were unloaded everything came apart easily. My truck is 12 months old and I store it indoors so no rust. 
 

First thing is to set up for the job on a flat, level surface with gas tank near empty, and measure the height of the front suspension. I measured from the bottom of the wheel to the fender edge to eliminate tire deflection as a variable. 
 

Next jack up the front of the truck. I jacked each side separately on the main frame member just forward of the transmission mount crossmember, and supported the frame on the actual front jack point just forward of that. You don’t need to jack the wheels off the ground - just raise the front end about 3 inches to mostly unload the suspension. The rest of the spring unloading can be handled at the torsion key. However, you do want to jack it up at least this high or the forces on the tool would be higher than I would be comfortable having. For safety, always keep your head, hands, and fingers where they won’t get hit if the tool suddenly fractures. There’s a lot of force and a lot of energy stored, and you never really know how good foreign steel is. 
 

I borrowed the torsion spring unloading tool from Autozone’s tool loan program. They have both the smaller and larger tools for GM trucks, but they don’t have them identified properly in their computer system. The tool you want is the larger one - the CTA 4045 pictured below. The smaller gray one won’t fit. I did not have any clearance problem with the exhaust system putting the tool in on the right side. I had at least 1/4” clearance.
 

i counted the turns when i removed the torsion key adjustment bolt on each side and used that as my starting point for the new springs. It ended up being within one turn to achieve the previous height with the new bars.
 

Once the adjustment bolts are unloaded by the tool, you back them all the way out, and remove the piece the bolts thread into (can’t remember the name). Then loosen the tool to completely unload the torsion spring. Repeat for the other bar. Now wiggle the torsion spring and shift it forward, being ready to catch the torsion key when it falls off the end of the spring. Repeat for the other spring. 
 

Removing the frame member that contains the torsion keys at the rear end of the springs was two bolts, not excessively tight. The cross member is not heavy but you need to support it when you remove the two bolts because it doesn’t have clearance to angle much to one side or the other. It needs to come relatively straight down.  
 

Once the cross member is out of the way, the torsion springs slide rearward and come out. The springs typically are not perfectly straight, and mine were installed with the bow upwards. I checked my new bars and put a mark on them and installed them the same way. It probably doesn’t matter, but that’s what I did. 
 

Reverse all of that to reinstall everything, and reload the torsion springs the same number of bolt turns as before as a starting point.  After you take the truck off the supports, you need to roll it forward a few feet and back to relax the tires and get an accurate initial height adjustment. 
 

My plan is to drive the truck a bit and check the adjustment. Since I’m putting it back at exactly the same height, I should not need an alignment, but I’ll post in a few days if that isn’t the case. 
 

The general ride feel after the change is a bit softer. It’s definitely noticeable but not a large change.  It is very noticeably softer when I hit a larger bump or dip in the road. 
 

Here are some photos from the job:  

 

 

Edited April 27, 2022 by Another JR

[Another JR]

More photos:

[sheath]

Nice work.

Looking forward to reading a 6 month drive report to see your satisfaction after some time on the truck.

[Another JR]

I took my Four Wheel Campers pop-up off the truck to do this job and to add an external gray water tank.  I’ll post on the ride/handling difference after I have it back on for a bit. 

[Another JR]

I’ve had the camper back on for a month now and just got back from a long highway trip.  (My loaded pop-up slide in camper puts 100 lbs on the front axle and 1700 lbs on the rear axle.).
 

The difference going back to the base torsion springs when driving at highway speeds is very noticeable when going over bumps and dips. The suspensions response is well matched front to rear now, and the truck does not pitch nose up when hitting dips and bumps.  
 

After this trip I’m definitely glad I made the change. The suspension feels “right” now.  I highly recommend that, if someone bought the snowplow suspension but isn’t going to install a plow and isn’t putting a very heavy load on the front suspension, they should consider installing the base front springs in their truck.  It took me 2 hours and $570 to change them. 

[Ray@Paula]

On 5/30/2022 at 11:11 PM, Another JR said:

I’ve had the camper back on for a month now and just got back from a long highway trip.  (My loaded pop-up slide in camper puts 100 lbs on the front axle and 1700 lbs on the rear axle.).
 

The difference going back to the base torsion springs when driving at highway speeds is very noticeable when going over bumps and dips. The suspensions response is well matched front to rear now, and the truck does not pitch nose up when hitting dips and bumps.  
 

After this trip I’m definitely glad I made the change. The suspension feels “right” now.  I highly recommend that, if someone bought the snowplow suspension but isn’t going to install a plow and isn’t putting a very heavy load on the front suspension, they should consider installing the base front springs in their truck.  It took me 2 hours and $570 to change them. 

Thank You Jon, Awesome job & write up!! I can definitely see that it was well worth the work along with price. It's nice to know that having an unwanted snowplow package can be dealed with if needed. Glad it all worked out with your camper... Nothing worse than a harsh ride traveling cross country. This thread is a keeper!! Tganks again. Ray

[AndrewF]

Great write up, spot on with the timing too. I just swapped my 6k lb plow package torsion bars for 4800 lb ones this morning. Only other thing I’ll add is the front of the bars are painted with a line so I lined up my new ones the same way. So the line straight up and down with the L/R directional stamp to the outside. 
 

Front end should flex a little better now!

 

 

Edited March 8, 2025 by AndrewF

[Chuck FB]

Last year as I was looking for information on the GM HD trucks, this was one of various threads and the topic of suspension that I was trying to sort out what made the most sense to buy if I had a choice ( and I did since I ended up ordering one vs something off the lot ). I don't know what future endeavours my truck may have but I really didn't feel the need to make a GM truck ride like the front end of a Ford super duty or at least how I know they rode just a few years back with the gas engine "like a dump truck". So based on feedback from here and other comments I felt it made the most sense in my situation to order the truck with the standard torsion bars. The only downside I can see is GM then puts a sticker on the truck claiming it doesn't give it any weight rating at all for hauling a camper.

 

Andrew, if you happened to see my question I was wondering if you have a micrometer or accurate vernier caliper that you could measure the diameter of the 6000 lb rated bars as well as your new 4800 rated ones. Mine are the 4800 lb rated units according to the pillar sticker and I come up with a diameter of about 1.523 thousands with a micrometer. One bar is 1 thou different than the other, manufacturing tolerances.

 

One thing that I still have never had a definitive answer over and that is what diameter the Cognito comfort ride torsion bars are as they only mention fitting on a whole list of trucks from 2020 up to 2025, they never say a word about what engine the truck has as per compatibility since that makes a significant difference, nor what the spring rating is. I even sent them a note quite some time ago and I heard crickets. Some have even even had the feeling from the markings on their bars that they may be a GM bar but I can't confirm that either. They only state that their bars feature a reduced rate over the OEM bars but which OEM bars !, I think there are 5 different ratings that GM has on these bars depending on wheel base and engine choice and plow package etc, from 4400,4800,5200,5600,6000

 

Going back to my new truck as well as a prior GM branded truck from years ago also with the torsion system, GM does a crappy job of levelling the trucks from side to side on the front end, some trucks come off the line fine while others are quite out of wack, my old one as well as this new one was certainly far from adjusted evenly height wise from side to side and the adjust bolt differences helped back that up. While I had no intent of "levelling" the truck front to back as all that does is make a harsh ride with the keys cranked right up and give the suspension and steering a short life on the front anyway, I wanted the truck to at least sit level from side to side ... its a new truck after all. When it sat on a level floor I could also see the difference in the space or lack of on the jounce bumpers from the higher side to the lower side. I measured the rear from side to side and it was being twisted over as well from the gross difference in the front factory adjustment. The guide I used to do the actual adjustment was the fender opening to center of hub distance, it can't be too far out doing it that way. It took a total of 4 1/2 turns "in" on the right side and a 1/2 a turn "out" on the left side to get to level across and I ran the truck some on the road after the adjustment just to work the suspension and then measure again and its bang on, so is the rear now from side to side. After the truck gets a few miles on it I will probably take it into an independent alignment shop in case they have to make slight adjustments to the caster or camber and before I did any adjusting I see the steering wheel is off ever so little to the left, I swear GM lines up the steering wheel to the cockyed steering cowling they designed. It steers exactly how it did before I touched the torsion key adjusters so I can't have thrown it off too much. I should also add that the high side had been 24 3/4" and I had read where its said a good high end goal OEM wise would be 25" and so that is what I chose but could have evened it up to the 24 3/4 instead and would have meant less turning up of the right side. I expect them to sag down a bit as the truck gets used so should be quite fine.

[newdude]

13 minutes ago, Chuck FB said:

Going back to my new truck as well as a prior GM branded truck from years ago also with the torsion system, GM does a crappy job of levelling the trucks from side to side on the front end, some trucks come off the line fine while others are quite out of wack, my old one as well as this new one was certainly far from adjusted evenly height wise from side to side and the adjust bolt differences helped back that up. While I had no intent of "levelling" the truck front to back as all that does is make a harsh ride with the keys cranked right up and give the suspension and steering a short life on the front anyway, I wanted the truck to at least sit level from side to side ... its a new truck after all. When it sat on a level floor I could also see the difference in the space or lack of on the jounce bumpers from the higher side to the lower side. I measured the rear from side to side and it was being twisted over as well from the gross difference in the front factory adjustment. 

 

 

The side to side is intentional to compensate for full fuel tank and driver weight when going down the road.  Driver side is adjusted slightly higher.  They've never left the factory 100% dead level side to side.  

[Chuck FB]

1 hour ago, newdude said:

 

 

The side to side is intentional to compensate for full fuel tank and driver weight when going down the road.  Driver side is adjusted slightly higher.  They've never left the factory 100% dead level side to side.  

I hear what your saying and while that makes sense ( depending on how the seating is used in the truck ) mine was way way off of some slight compensation, had it been slight I would not have concerned myself with it but this was more than I could personally turn a blind eye to ( at least I don't think I have OCD ! ). With our crowned roads it would just exaggerate it even more. Also and not that this is important but due to how the box is shaped internally at the left front corner as it takes up room because of the fuel filler on the outside of the truck, the right hand front box corner lends itself better to items that will fit that I want to carry with me on a general basis that will add up in some weight so in the end the left/right balance with just a driver should be fairly neutral. I forgot to mention that when I did the measuring and adjusting, the fuel tank was completely full.

 

The good part about the GM with the torsion bar system is that it can be adjusted to fine tune height and any lean or correct for some suspension sag over time, the same can't be said of a solid front axle system.

 

The truck I mentioned from years back, it had a horrible lean from new to the drivers side instead and my brother had bought an exact model and year truck as well and his sat perfectly level. What made it a real head scratcher was that the rear of the truck leaned even more than the front and I thought there must be something not matched with the rear spring packs so I went through the work of swapping them side to side ... made zero difference. Then I focused on the front and after experimenting in levelling the front, it brought that back end around to level as well. I would have sworn that was physically impossible but yet it all worked out once I set it level. I could just feel and visually see it in my older truck as I drove down the road and sitting on a flat cement shed floor looking at it from the outside it looked pathetic, like something had failed in the suspension.

Edited March 9, 2025 by Chuck FB

[Another JR]

11 hours ago, AndrewF said:

Great write up, spot on with the timing too. I just swapped my 6k lb plow package torsion bars for 4800 lb ones this morning. Only other thing I’ll add is the front of the bars are painted with a line so I lined up my new ones the same way. So the line straight up and down with the L/R directional stamp to the outside. 
 

Front end should flex a little better now!

 

 

Going from 6000 lb bars to 4800 lbs is a big change. Are 4800 bars the base bars for your truck configuration (minus plow or camper package)?  I thought the maximum addition with the plow package was two steps up in spring rating. Camper package is one step. 
 

The base spring rating doesn’t leave much room for payload (including passenger weight) before you run into the FGAWR. I wouldn’t want to go below the base spring rating. 
 

I don’t think the marked line on the front spring end means anything for orientation.  I suspect it’s like a torque stripe, allowing inspector confirmation that the system was adjusted to spec by the assembler.  I oriented mine putting the curvature upward. Rotational orientation shouldn’t matter.

[Chuck FB]

Jon I hope you don't mind me butting in as I can post some GM information on their ratings. I would have thought as well logically they would go in equal steps but for whatever reason the optional spring ratings don't follow that pattern on all the trucks and I am going to attempt to attach a pdf that I came across somewhere online and thought it had been this forum but might have been another, I assume its something GM themselves publish but I don't know where to access it on a GM website. This pdf shows the 3500 single wheel in all its wheel bases as well as the 3500 dual wheel on the lower of the two charts. Note how the dually diesel CC has the max rated bars as standard so there is no going up in rating. But like my truck configuration being a short box crew cab 3500 gas, 4800 being the base and then 5200 for the camper only bars, then jumping up to the maximum 6000 for the plow package. Makes no sense in my mind as how can a gas engine front end require the same 6000 rated bars as a diesel for the plow as there is quite a difference as far as I know in the actual physical front end weight between the gas and diesel. Granted I have not driven my truck much yet on various crap frost heave roads but its easy to tell that its no mushy compliant half ton, it would be interesting to test drive my same truck with the plow bars ( or maybe not ! ). I also have the ratings for the various 2500 configurations but that just adds to the confusion unless someone wants me to post them in another comment.

2024_Chevy_Silverado_3500_HD_VYU.pdf

[Another JR]

2 hours ago, Chuck FB said:

Jon I hope you don't mind me butting in as I can post some GM information on their ratings. I would have thought as well logically they would go in equal steps but for whatever reason the optional spring ratings don't follow that pattern on all the trucks and I am going to attempt to attach a pdf that I came across somewhere online and thought it had been this forum but might have been another, I assume its something GM themselves publish but I don't know where to access it on a GM website. This pdf shows the 3500 single wheel in all its wheel bases as well as the 3500 dual wheel on the lower of the two charts. Note how the dually diesel CC has the max rated bars as standard so there is no going up in rating. But like my truck configuration being a short box crew cab 3500 gas, 4800 being the base and then 5200 for the camper only bars, then jumping up to the maximum 6000 for the plow package. Makes no sense in my mind as how can a gas engine front end require the same 6000 rated bars as a diesel for the plow as there is quite a difference as far as I know in the actual physical front end weight between the gas and diesel. Granted I have not driven my truck much yet on various crap frost heave roads but its easy to tell that its no mushy compliant half ton, it would be interesting to test drive my same truck with the plow bars ( or maybe not ! ). I also have the ratings for the various 2500 configurations but that just adds to the confusion unless someone wants me to post them in another comment.

2024_Chevy_Silverado_3500_HD_VYU.pdf 86.67 kB · 2 downloads

Understood and thanks for posting the info. 
 

It’s interesting how, doing the math now, taking my 3500 cclb srw gas empty axle weights and changing the wheelbase from 172 to 159 inches, the wheelbase change alone makes AndrewF’s front axle weight about 350 lbs lower than mine. Hence the 4800 lb springs.  I would have guessed the effect was less. 

[AndrewF]

2 hours ago, Another JR said:

Understood and thanks for posting the info. 
 

It’s interesting how, doing the math now, taking my 3500 cclb srw gas empty axle weights and changing the wheelbase from 172 to 159 inches, the wheelbase change alone makes AndrewF’s front axle weight about 350 lbs lower than mine. Hence the 4800 lb springs.  I would have guessed the effect was less. 

Yep the base springs for my 2500 reg cab 10650 gvw are 4800 lbs. I am surprised as well that the plow package springs for my truck were the heaviest possible being that my front end is the lightest. On the 3500 srw/drw reg cab chart it looks like 4800lb is still standard too 

 

I debated doing 5200 lb ones but I did some math a while back and the 4800 lb ones still left me with a decent amount of capacity even with 2 people in the cab. 

[Chuck FB]

I am curious what your two trucks weights are on the front axle when typically loaded with the people in the cab normally driven with as well as whatever sits in the back seat ( and under it ) as well as whatever is carted around in the box. Like you said Jon, with your truck being a long wheel base its slightly heavier over all vs the short box but its that wheel base that transfers more of the rear weight onto the front axle due to the rear axle effectively slid further back.

 

I am guessing ( based on youtubers that show the weight stickers on trucks with my same wheel base and gas but with different trim levels and options ) that my truck is a little heavier than some due to the particular options. My factory curb weight is listed as 7687 pounds and although its a high country which means "so called" leather seats, I do not have the added weight of a sunroof. It has the factory base running boards so not the electric ones, the spray in bed liner and the trailer prep package which I imagine has a bit of heft to that metal assembly. But what my truck has which puts extra weight specifically on the front is the second battery and the two alternator setup. I believe my trucks weight rolling out the factory vs a low trim level truck without the fifth wheel prep etc is around 500 pounds lighter.

 

Then items I have added since I bought it have pushed the weight up such as a full set of kick back mud flaps, the GM rubber interior mats front and back ( the stock factory mats are a total joke as I found out ), added the full size under seat rear storage box and have it filled with items, and have a bakflip cover on the box as well as a GM rubber box floor mat and those certainly have some weight to them. The weight starts creeping up and that doesn't include tools and extra fuel I will be adding into the box in the near future. I weighed the truck the other day with the items added so far and with a full tank of fuel and just myself in it, I was 4475 lb on the front and 3615 on the rear.

 

Will I end up meeting or exceeding the 4800 lb at times with items forward in the box or with passengers, its very possible and yet I can't say I am too worried about it simply because its really a 6000 pound rated front axle component wise truck other than the torsion bar rating. And that also brings me back to what the heck is the size/rating of that cognito set of bars, I had heard some unconfirmed measurements of it being somewhat smaller in diameter then these 4800 rated bars but whatever it is, some guys are putting them under trucks that have the diesel engine and remarking how much better their truck rides over whatever bars their truck came with.