2023 LTZ 3500 - Leaf springs are bagged!?

[PBNB]

I bought my truck a year ago and haven't driven it a ton (10k kms) 

 

My truck has was level when I got it so I thought it was something to do with the Z71 trim or the previous owner levelled it. 

 

During some highway driving we had some floating so I started looking into shocks to handle some of the rebound that the Ranchos seems to be missing.

 

I think I have found out why the truck is level, the leaks are worn. I don't have lowering shackles and do have the full set of leafs with the overloads intact. When measuring the hub to fender, I get just over 24" in the front and about 1/2" lower in the back. 

 

My plan was to add some keys to push up the front about 1.5" and add some upper control arms to give the slightly longer shocks room to move.

The rear was going to get the slightly longer shocks.

 

The truck has 30k miles on it so it seems that the leafs shouldn't be toast. Would there be any other reason to why the rear is sitting low. The truck has the 5th wheel prep if that makes a difference.

 

Any ideas would be helpful. Currently I am looking at changing out the leafs to get the missing 3" of height back.

[Chuck FB]

5 hours ago, PBNB said:

I bought my truck a year ago and haven't driven it a ton (10k kms) 

 

My truck has was level when I got it so I thought it was something to do with the Z71 trim or the previous owner levelled it. 

 

During some highway driving we had some floating so I started looking into shocks to handle some of the rebound that the Ranchos seems to be missing.

 

I think I have found out why the truck is level, the leaks are worn. I don't have lowering shackles and do have the full set of leafs with the overloads intact. When measuring the hub to fender, I get just over 24" in the front and about 1/2" lower in the back. 

 

My plan was to add some keys to push up the front about 1.5" and add some upper control arms to give the slightly longer shocks room to move.

The rear was going to get the slightly longer shocks.

 

The truck has 30k miles on it so it seems that the leafs shouldn't be toast. Would there be any other reason to why the rear is sitting low. The truck has the 5th wheel prep if that makes a difference.

 

Any ideas would be helpful. Currently I am looking at changing out the leafs to get the missing 3" of height back.

 

Although my truck isn't exactly like yours since I have the gas engine and therefore the 11.5 rear axle, otherwise if yours is a crew cab with the standard 6'10" box length it would be very similar otherwise as yours being a Chev also will have the same fender profile as the GM probably measures slightly different. I do have the Z71 package but being a High Country that only adds on the rancho shocks and the so called skid plates as mine already came with the 20" wheels where your trim probably added the wheels with its Z71. Pretty much semantics with that Z71 as it does nothing for the actual fender to hub distance.  Like some trucks seem to be from the factory, mine was not even from side to side on the front for the torsion key adjustment ( just sloppy workmanship setting it up ) as the low side was 24 1/4 and the high side was 24 3/4 from brand new. I would say that yours probably has settled in and may have been 24 1/2 or slightly higher give or take when new. What I did with mine and this was based off of information from companies that make lifts as well as work with these trucks a lot and the recommendation was not to go higher than 25 inches on the front in order to retain close to that 3 inches of droop travel and also to retain the good cv and tie rod angles. Just my two cents, I would recommend you save your money and not bother changing anything parts wise on the front end for UCA and just replace or maybe you already have replaced the shocks with a factory length/non lift shock of whatever brand you go with. I would be surprised if your keys would not have enough adjustment to bring you up to that 25" or close to that height. Droop travel is important, I know what its like from a prior truck in cranking them up and not having the best droop travel and as well the ride gets stiffer as one cranks it up too much due to the angles that develop. I did get my truck realigned after I increased the height but it really had not thrown anything out much at all but it would have had I continue to lift it up more. 

 

The rear, that is a good question as to what happened there and it would almost seem like the springs did sag out some but I doubt as much as you are assuming they have. Now again with my truck I had a bak flip and thick rubber mat and rear flaps which are somewhat substantial installed before I was able to do the measuring and my truck also has the fifth wheel prep and the spray in liner which all adds to the weight. I was sitting at around 25 1/8 from fender to center of hub on the rear with those mentioned items on the truck. So your truck is measuring about 1 1/2 inches or so lower in the rear as a comparison with the figures I have to work with on mine. I can only speculate that they were either hauling something heavy in the back of that truck or they had a heavy ball hitch trailer or a heavy fifth wheel trailer and the springs never bounced back from that weight. Your probably right that the ideal thing to do would be to install new main packs and add the existing top overload springs to the pack. Just to be sure as per your main pack ( not the two thin upper overloads that hit the frame pads ) that you have what they refer to as a 4 + 1 spring pack. Another words the thick tapered bottom leaf with four leafs of varying length of the same thickness that sit on top of that bottom overload spring. There would be a way of raising your rear end some if you felt the rear springs were still serviceable and didn't want the hassle of swapping them and that is to round up the special spacer block that has the hole on the topside and the stud shape on the bottom that engages the axle spring pad perch that is welded to the axle housing, then using longer Ubolts to fasten your leaf packs down. Perhaps a spring shop that is familiar with the GM trucks might be able to shed some light on if this is a common thing for the springs to take a sag and if a lift block would be ok or if you should start out fresh. I guess it depends on what your doing to do with the truck use wise. 

 

Mind you I have to ask since you never said one way or the other, this is a single rear wheel truck and not a dually ?. Oddly enough the dually is a 3 + 1 main pack and then 3 upper overload springs. 

[AndrewF]

17 hours ago, PBNB said:

I bought my truck a year ago and haven't driven it a ton (10k kms) 

 

My truck has was level when I got it so I thought it was something to do with the Z71 trim or the previous owner levelled it. 

 

During some highway driving we had some floating so I started looking into shocks to handle some of the rebound that the Ranchos seems to be missing.

 

I think I have found out why the truck is level, the leaks are worn. I don't have lowering shackles and do have the full set of leafs with the overloads intact. When measuring the hub to fender, I get just over 24" in the front and about 1/2" lower in the back. 

 

My plan was to add some keys to push up the front about 1.5" and add some upper control arms to give the slightly longer shocks room to move.

The rear was going to get the slightly longer shocks.

 

The truck has 30k miles on it so it seems that the leafs shouldn't be toast. Would there be any other reason to why the rear is sitting low. The truck has the 5th wheel prep if that makes a difference.

 

Any ideas would be helpful. Currently I am looking at changing out the leafs to get the missing 3" of height back.

You can't measure to the fender to figure out level on these trucks.  The rear wheel/fender is set lower in the back than on the front.  

 

For example, if I put a laser level on the truck to follow the bed rail, my truck is ~3.5" lower than the rear.  But if I measure wheel well to wheel well front to back, it only shows ~1" difference. If you go to the bodybuilder manual (GM Upfitter) it will give you some measurements from the frame to see if you're out of spec. 

Edited November 17, 2025 by AndrewF

[Chuck FB]

44 minutes ago, AndrewF said:

You can't measure to the fender to figure out level on these trucks.  The rear wheel/fender is set lower in the back than on the front.  

 

For example, if I put a laser level on the truck to follow the bed rail, my truck is ~3.5" lower in the rear.  But if I measure wheel well to wheel well front to back, it only shows ~1" difference. If you go to the bodybuilder manual (GM Upfitter) it will give you some measurements from the frame to see if you're out of spec. 

 

Your right, I never commented on that aspect although suspected an assumption that he assumed his front and rear fenders would be at the same height if the truck was level and therefore expecting the rear measurement to be much higher than it is. Never the less just going off of what he said measurement wise, it would at least seem that his rear springs have settled a lot due to a prior load it probably carried. If he did as he was thinking in raising the front, that really would make his truck look front end high and at that point may actually be front end high. I might be thinking wrong in terms of what is "level" on one of these trucks but I've assumed it would be the main portion of the frame under the cab that is straight, and if its parallel to the ground front to rear that would be level ?.  The fender height would be way out of whack at that point per a visual standpoint and make the rear look much lower than it actually is. 

[PBNB]

2 hours ago, AndrewF said:

You can't measure to the fender to figure out level on these trucks.  The rear wheel/fender is set lower in the back than on the front.  

 

For example, if I put a laser level on the truck to follow the bed rail, my truck is ~3.5" lower in the rear.  But if I measure wheel well to wheel well front to back, it only shows ~1" difference. If you go to the bodybuilder manual (GM Upfitter) it will give you some measurements from the frame to see if you're out of spec. 

Thanks, this is good info to investigate. My measurements were taken from the hub to the bottom of the fender on both front and rear. Where the challenge comes in is the rake that these trucks come with doesn't seem to be there.  Looking at other Silverados, they seem to have a visual rake rear to front. 

[PBNB]

9 hours ago, Chuck FB said:

 

Although my truck isn't exactly like yours since I have the gas engine and therefore the 11.5 rear axle, otherwise if yours is a crew cab with the standard 6'10" box length it would be very similar otherwise as yours being a Chev also will have the same fender profile as the GM probably measures slightly different. I do have the Z71 package but being a High Country that only adds on the rancho shocks and the so called skid plates as mine already came with the 20" wheels where your trim probably added the wheels with its Z71. Pretty much semantics with that Z71 as it does nothing for the actual fender to hub distance.  Like some trucks seem to be from the factory, mine was not even from side to side on the front for the torsion key adjustment ( just sloppy workmanship setting it up ) as the low side was 24 1/4 and the high side was 24 3/4 from brand new. I would say that yours probably has settled in and may have been 24 1/2 or slightly higher give or take when new. What I did with mine and this was based off of information from companies that make lifts as well as work with these trucks a lot and the recommendation was not to go higher than 25 inches on the front in order to retain close to that 3 inches of droop travel and also to retain the good cv and tie rod angles. Just my two cents, I would recommend you save your money and not bother changing anything parts wise on the front end for UCA and just replace or maybe you already have replaced the shocks with a factory length/non lift shock of whatever brand you go with. I would be surprised if your keys would not have enough adjustment to bring you up to that 25" or close to that height. Droop travel is important, I know what its like from a prior truck in cranking them up and not having the best droop travel and as well the ride gets stiffer as one cranks it up too much due to the angles that develop. I did get my truck realigned after I increased the height but it really had not thrown anything out much at all but it would have had I continue to lift it up more. 

 

The rear, that is a good question as to what happened there and it would almost seem like the springs did sag out some but I doubt as much as you are assuming they have. Now again with my truck I had a bak flip and thick rubber mat and rear flaps which are somewhat substantial installed before I was able to do the measuring and my truck also has the fifth wheel prep and the spray in liner which all adds to the weight. I was sitting at around 25 1/8 from fender to center of hub on the rear with those mentioned items on the truck. So your truck is measuring about 1 1/2 inches or so lower in the rear as a comparison with the figures I have to work with on mine. I can only speculate that they were either hauling something heavy in the back of that truck or they had a heavy ball hitch trailer or a heavy fifth wheel trailer and the springs never bounced back from that weight. Your probably right that the ideal thing to do would be to install new main packs and add the existing top overload springs to the pack. Just to be sure as per your main pack ( not the two thin upper overloads that hit the frame pads ) that you have what they refer to as a 4 + 1 spring pack. Another words the thick tapered bottom leaf with four leafs of varying length of the same thickness that sit on top of that bottom overload spring. There would be a way of raising your rear end some if you felt the rear springs were still serviceable and didn't want the hassle of swapping them and that is to round up the special spacer block that has the hole on the topside and the stud shape on the bottom that engages the axle spring pad perch that is welded to the axle housing, then using longer Ubolts to fasten your leaf packs down. Perhaps a spring shop that is familiar with the GM trucks might be able to shed some light on if this is a common thing for the springs to take a sag and if a lift block would be ok or if you should start out fresh. I guess it depends on what your doing to do with the truck use wise. 

 

Mind you I have to ask since you never said one way or the other, this is a single rear wheel truck and not a dually ?. Oddly enough the dually is a 3 + 1 main pack and then 3 upper overload springs. 

Thanks for this reply, Mine is a SRW and the pack is 4 + 1 with the extra 2 overloads above the main pack.

The enhancement to the suspension is what got me looking at the rear. 

 

The plan was to put slightly longer shocks front and rear. New upper control arms and new keys that will kick the front up about 1 1/2". This is when the tape measure came out. 

 

The shop helping me with this was also surprised that the rear seemed low. 

[PBNB]

2 hours ago, AndrewF said:

You can't measure to the fender to figure out level on these trucks.  The rear wheel/fender is set lower in the back than on the front.  

 

For example, if I put a laser level on the truck to follow the bed rail, my truck is ~3.5" lower in the rear.  But if I measure wheel well to wheel well front to back, it only shows ~1" difference. If you go to the bodybuilder manual (GM Upfitter) it will give you some measurements from the frame to see if you're out of spec. 

I had a look at the bodybuilder website and can't seem to locate the "frame to ground" dims? I think a quick trip to the dealership might be good to get the numbers from a new truck. 

[PBNB]

@AndrewF, I was able to find the resource in the bodybuilder HD document. It looks very helpful and clearly shows the difference front to back. I will check out a few more things. Seems like I am back on track as far as getting my suspension dialled in! 

[asilverblazer]

A couple points regarding most of the measurements and body builder data. 

 

Generally, there is no "level" on the trucks or data.

 

There are some common measurements though. If memory serves, most height measurements are taken from a common height on the side profile - typically the center of the hubs - elevation 450 (mm). From that line they measure up to other points on the frame and/or body.

 

The resulting measurements would not necessarily be accurate to any particular truck due to a variety of other factors, weight, usage, age, etc. I would call them 'design' measurements.

 

How to tell if your truck is low, too low, etc? Compare your truck to as many others that are configured as close to yours as possible. The easy measurement would be from ground to fender line. Better would be from top of axle to bottom of frame, which would be common between Chevrolet and GMC. 

[Chuck FB]

9 hours ago, PBNB said:

Thanks for this reply, Mine is a SRW and the pack is 4 + 1 with the extra 2 overloads above the main pack.

The enhancement to the suspension is what got me looking at the rear. 

 

The plan was to put slightly longer shocks front and rear. New upper control arms and new keys that will kick the front up about 1 1/2". This is when the tape measure came out. 

 

The shop helping me with this was also surprised that the rear seemed low. 

 

Ok so it should be very much like mine and if its a crew cab standard box then its exactly like mine for all intended purposes dimension wise. Where it would be different is the rating of your front torsion bars being the diesel so they are more than likely 5600 pound rated ( you can look at your front axle weight rating on the door post sticker ) but again that is just to carry the extra weight of the diesel and in the end is adjusted the same as the gas version height wise. Like I mentioned about doing anything radical with the front, there are these youtube channels out there pushing "leveling kits" like crazy because they sell them so of course they will spew bs about how great it is but they end up making the ride stiffer and they crank them too far and they don't have much suspension droop left. And all the high wear that then takes place with the tie rods and center link, the pitman arm ball joint, the drag link ball joint all take a real beating with angles they were never designed to run at and last. Outfits that sell the leveling kits don't want to hear talk like that. 

 

Perhaps if you explain what type of use you plan on for your truck on here, that might help as a few on this site have recently put a different brand of rear leaf spring pack on that at least in theory was designed for a better ride but with less weigh carry capacity, again all depends on what your future use is for your truck. 

[PBNB]

The sticker says 5,600 lbs for the front axle.

 

On our last trip out to Sask, we had some bouncing like the shocks (Z71 is supposed to have some fancy Ranchos) and the rebound was missing. The truck was bouncing and floating at times. 

 

I guess I just don't like that effect as I am used to much more control. 

 

So the plan is to get about 1 1/2" to 2" front level using SuspensionMaxx keys and Cognito upper control arms. Then installing the differential drop spacers to keep the CV's closer to stock angles. I was also looking at some adjustable King shocks.

 

That should allow the front suspension to move.

 

The rear gets new shocks as well. Once the front is done, I was going to see if it needed a little lift to still have a bit of rake. 

 

The Kings should take care of the lack of rebound. 

 

We mostly tow our smaller travel trailer and carry about 400 lbs over the bed of the truck almost all the time.

 

What do you think? 

[Chuck FB]

15 hours ago, PBNB said:

The sticker says 5,600 lbs for the front axle.

 

On our last trip out to Sask, we had some bouncing like the shocks (Z71 is supposed to have some fancy Ranchos) and the rebound was missing. The truck was bouncing and floating at times. 

 

I guess I just don't like that effect as I am used to much more control. 

 

So the plan is to get about 1 1/2" to 2" front level using SuspensionMaxx keys and Cognito upper control arms. Then installing the differential drop spacers to keep the CV's closer to stock angles. I was also looking at some adjustable King shocks.

 

That should allow the front suspension to move.

 

The rear gets new shocks as well. Once the front is done, I was going to see if it needed a little lift to still have a bit of rake. 

 

The Kings should take care of the lack of rebound. 

 

We mostly tow our smaller travel trailer and carry about 400 lbs over the bed of the truck almost all the time.

 

What do you think? 

 

Your truck would have the standard torsion bars for the crew cab short box, actually it would only be the dually or if a snow plow prep package was on it that it would have had the maximum 6000 rated torsion bars. 

 

I've had some experience but with a half ton with 9000 rancho's, they worked ok but they have their own issues as per the adjuster seizing up. From what I hear and be it on this forum or others, the stock ranchos that come on the Z71 are just an economy shock that seems to wear out awfully quick, its all hyped up with vehicle manufacturers claiming its something great but its smoke and mirrors. I have few km's on my truck so its not given my factory rancho's the chance to fall apart yet but new out of the box they seem fine as per controlling the weight of a factory sized tire/wheel combo on a nearly empty truck but I realize at some point I will have to be replacing them with something and I don't plan on modifying my suspension beyond my slight turning up/evening up the torsion bar height I already have done. I may try out a set of Bilstein 4600's as the 5100's are said to be by some and also by Bilstein themselves to be somewhat more firm and its the 5100's that can be had in longer lengths for lifted vehicles as the 4600 is for stock height only. In theory the stock length shock on the front with the stock UCA and the UCA stop still in place should not hinder the suspension travel. 

 

So the company or shop you have been talking to, would they or if you do the work yourself be planning on cutting the UCA droop stop pad that is welded to the frame off ?. I am not sure if aftermarket UCA's allow for any more droop travel "if" the stop is still in place, they would however help with that issue of the factory UCA ball joint angle being in a bind if the torsion bars are cranked up too much. 

 

Like I said, I don't have the experience at all with these new trucks, only an older truck but with the same theme in mind and finding out the downfall of limiting the droop travel as its more important then some give that part of the suspension travel credit for. I call these leveling kits the poor mans lift kit because they do cost a lot less than a full out lift that lowers all the pivot points and puts new steering knuckles on that corrects the operating angles of the tie rods and corrects the drive axles running angles. The problem with the poor mans kit is the suspension and drive axle parts that wear over time literally and ironically put one into the poor house with all the future parts that wear out and need replacing far more often. I haven't priced out King shocks for this application but whatever prices I have seen on that brand of shocks are typically insane and I have a hard time in my head putting on a low grade lift as it were with very expensive shocks in the hopes of coming out with a great end result. 

 

Again, those are just my thoughts and view point, take that for what its worth as others on here that have been dabbling in lifts and shocks may have come up with a decent middle ground with a combination of parts and within a certain height parameter over stock. 

 

Here's a video I believe i had linked in another thread on this forum, it shows the extreme of a torsion bar lift/level and yes some guys do that and it works great in the mall parking lot, it would be awful to drive in every day life. Vs an actual lift that really drops the diff down and all pivot points and replaces the knuckles etc and you can see the extreme difference in the angles from one lift style approach to the other with the same physical lift height. Also keep in mind that the larger shocks job is to help control larger/heavier tires over the stock size tires. 

 

 

 

[PBNB]

Cool video. 

 

I am not looking at maxing out the torsion bars. The Maxx keys are indexed so you can dial in a specific height and reinstall the keys. This way you don't max the torsion bar you just reposition it with the same or similar tension. I was looking at 1 1/2" adjustment to get the droop up. The shocks will add 1 1/2" up and down travel opening up the ride and getting the truck off the bump stops. The upper control arms help this as well as giving a better range of alignment adjustment for the new height. 

 

The Maxx kit comes with diff lowering spacers as well so the CV angles are close to stock. 

 

With all this, the rear should be higher by an inch or more after the front is adjusted. 

https://suspensionmaxx.com/product/1-inch-2.5-inch-leveling-kit-2020-silveradosierra-2500hd3500hd-maxx-cam-9-suspensionmaxx

 

I totally agree that the Z71 package is a bit of a joke and all I see are some white/rusty Ranchos. 

 

The rebound control is supposed to be very good with the shocks which is what I really wanted to improve on. I did upsize the tires to 295/70/18 Falkens but didn't want to go much bigger.

[Chuck FB]

I didn't think that was your plan as per cranking the heck out of the torsion bar keys to do what they demonstrated there but there are guys that do that and don't grasp why its just a bad idea in a few ways and then learn after their steering goes to crap and find out they have a lot of worn out parts with relatively few miles on them. And like I mentioned before I have a feeling from your front measurement that you are riding on the jounce bumpers a little more than what is ideal and all due to suspension taking a settle, the torsion bars that is. 

 

I'd be curious to know how many threads are visible on the factory torsion key adjuster bolts, one side will more than likely show a bit more thread than the other but I am guessing there is a certain amount of adjustment available within the stock keys/adjusters. 

 

Of course I can almost feel the itch you have to spend some ( I mean a lot )  Canadian monopoly money on US priced parts LOL. 

 

I will say that sounds like an excellent tire size for the reason that its just slightly taller than the 20" wheel stock tire but a bit wider tire and a lot taller side wall because of being on an 18" rim. That gives you a higher carrying capacity tire assuming it is the E rated LT tire and I believe it is since that is the only type/size listed for Falken under the AT4W tire if that is the model you have. An opportunity to run lower pressures over the door sticker pressures and in your case not loading the truck down heavy on the rear, quite a lot lower than that 80 pounds by a wide margin and even some on the front. The lower the tire pressures the more the tires become a part of the better ride and less work the shocks have to do in controlling an over inflated basket ball, if that makes sense. I have talked about this before on this forum and it takes weighing the individual axles with the weight that is planned to be run and then using a tire inflation guide for the size of tire being run to find the minimum safe tire pressure to run at highway speeds for the weight being carried. Another words doing it the safe way without guessing and running too low a tire pressure and risking a blow out. 

 

There is a thread going in the next main heading down under the 20 to 24 HD trucks category "mods" where a member is going to be installing a leveling kit on an HD shortly and will have photos up and so forth, that could be informative for you to look over once that is posted after the install. 

[asilverblazer]

Why are you raising the front? Its sounds like you are spending a bunch of money to correct the resulting problems from lifting the front and 'wishfully' improving the ride at the same time. Especially since your concerns seem to stem from the rear - at least that's what you talking most about.

 

The trucks are very heavily sprung - and the jounce bumpers in the front (on the lower control arm) are not strictly bump stops but have a role in suspension too.