Uneven rear suspension

[Homer1959]

Hi, first post here. French canadian so please be patient with my english  

I bought my new Sierra HD2500 SLE Gas in april 2025. I am in love with this truck, is it going to last ... well only time will tell.

 

I come for an F150 XLT 2014 3.5 eco. This truck served me well but was starting to be unreliable. I was hauling a travel trailer of 7500lbs 30 foot long , and even being maxed out it was ok to drive our 8000km trip down to texas every year I looked a the f250 but not much difference with the interior and exterior so i decided to give a chance to GMC... 

 

ok enough of me, now tell me I am setting up my equalizer hitch and I realized that when I measure (unloaded) the rear height from the fender wheel well that I get 1 1/2 higher on the r/s versus the l/s. have you ever noticed something similar ?

 

The truck drive straight, no problem detected, I measure also from the frame and the bumper and its consistant, always higher on the r/s. I also noticed the the helper spring is closer to the leaf spring on the l/s .... so if I am not asking for too much can you take the measurment to confirm that yours sit level or not like mine , that would be really appreciated . Im leaving for a 700 miles trip with the trailer and the truck fully loaded maybe that all i need to put everything under there in the right place ?  

Depending of your feedback I might pay a visit to my dealership. thanks in advance  

 

[Pryme]

Welcome to the forum. My 2022 2500 measures exactly the same. From the uppermost point in the rear wheel well to the concrete floor of my level garage it is 41 1/4” 

 

make sure you’re on a flat concrete or asphalt surface when you measure. If you are and it’s an inch and a half off there is a problem. 

[Homer1959]

In my case its 40.5 l/s. 42 r/s ... I think a visit to my dealership will be in the plan thanks Pryme 

Edited August 15, 2025 by Homer1959

[Pryme]

32 minutes ago, Homer1959 said:

In my case its 40.5 l/s. 42 r/s ... I think a visit to my dealership will be in the plan thanks Pryme 

Yeah that’s not right. Something is wrong with the suspension. Let us know what it ends up being. 

[Another JR]

Make sure the part numbers on your left and right rear spring assemblies match. They are painted in large numbers on the bottom. The gas tank is on the left side, so measuring with a full tank will cause the left side to be slightly lower, but I wouldn’t think that would cause 1.5 inches of difference. Also, don’t accept the dealer adjusting the front torsion bars to compensate if the rear suspension is really the cause for the lean. 

[Homer1959]

the front is almost perfect so if they touch the torsion bar they will screw up the front but thanks for the heads up , its something that I will discuss with them  btw same part number confirmed

 

 

left side helper spring is almost touching leaf spring on the other side the gap is much more important, anyway I contacted the dealer for an appointment 

 

Edited August 15, 2025 by Homer1959

[Handy]

What do you think about Jon's comment about the gas tank being on that side?

 

I am experiencing the same thing on my 2013 C3500 right now and am curious what you find out.  It is a service truck, so my first thought was an uneven load in my cabinets, but I have ruled that out and actually have more weight on the right side now with no change to the 1 1/4" inch difference, and helper spring gap as you have described.  I have been wondering if my leaf springs are worn out, but you have new leaf springs, so I am curious what you find.  My search online revealed a lot of comments about a classic Chevy lean due to the fuel tank being on one side.  I have been driving Chevy trucks for 40 years and have never experienced a Chevy lean until now.

[Homer1959]

On 8/19/2025 at 9:44 PM, Handy said:

What do you think about Jon's comment about the gas tank being on that side?

 

I am experiencing the same thing on my 2013 C3500 right now and am curious what you find out.  It is a service truck, so my first thought was an uneven load in my cabinets, but I have ruled that out and actually have more weight on the right side now with no change to the 1 1/4" inch difference, and helper spring gap as you have described.  I have been wondering if my leaf springs are worn out, but you have new leaf springs, so I am curious what you find.  My search online revealed a lot of comments about a classic Chevy lean due to the fuel tank being on one side.  I have been driving Chevy trucks for 40 years and have never experienced a Chevy lean until now.

My truck is going to the dealership on Monday, but I’m not expecting much. I assume they’ll just say, "it is what it is." I’ve measured around 10 HD trucks on their lot, and none are perfectly even on both sides—they vary from 1/2 to 1 inch. Mine, however, is at 1 1/2 inches. Bent frame? I’m not sure. I’m curious to know what specifications these trucks are supposed to meet on a frame machine—GM must allow for pretty wide tolerances. 

[Homer1959]

The truck will be back tomorrow. According to the verdict, it falls within GM spec. The advisor sent me the GM diagnostic procedure with all the measurements, and my left rear, front left, and right sides are spot on. However, according to MY measurement the rear right is outside the spec. The rear should be 42 inches ± 1/2 inch, but my rear right side is 1 to 1 1/4 inches higher than the left side. They assured me they took their measurements on their alignment pit and confirmed the truck is square, so there’s not much they can do. I’ll double-check tomorrow, though I’m pretty sure the truck isn’t square. Even if I’m right, they can’t lower the rear—raising is possible, but lowering isn’t. Anyway, I’ll leave it as is; it’s not a big deal since the truck tracks straight and everything else is fine.

[Chuck FB]

I had a couple of thoughts and one of them was to make sure the tires measure the same height on each axle, that of course is a real long shot but how crazy could it be if there was a tire that was physically a different size, the odds would be very low though. Also when you have the truck on a level pad, measuring the fenders again but also measure from a location on the frame to the cement on both sides and being that the frame is inboard of the fenders it won't show as an exaggerated measurement. I've wondered also if there was something off with the box to frame mounds causing that height discrepancy. But you might have a bit of a mismatched ( in manufacturing ) rear spring pack, I don't know if that is possible or not but again just another thought. 

 

My new truck was not level either from side to side but I soon could see what was highly likely as the culprit and that was a poor setting of the front torsion bars and the massive difference in the exposed threads on the torsion key bolts was very telling and also the difference in gap at the jounce bumpers. My right side was lower over all, the front right was a 1/2 inch low and the right rear was around 3/8 or so. I adjusted them ( lifted the truck off the cement first ) and I did choose to raise the front just slightly ( that maximum 25 inch to hub ) which was only a 1/4" higher than what the left side started out like from the factory but that was my personal choice to do that as I could have stayed within the factory height. Changing the front as I did brought the rear into the same height so that was that. I did have the alignment checked after as my steering wheel was off from the day I test drove it so they corrected that and that's all they had to do but the truck before and after my adjustment drove straight as an arrow so nothing changed with that aspect. I made sure to have a full tank of fuel when doing the measurements so I didn't end up with a left side lean after all of that. 

 

I went through a situation with a new older chev half ton pickup years ago and it was leaning to the left and would have sworn it was the rear leaf springs ( I even went through all the work to swap them side to side ) and that made zero difference after all that work but that made me look harder at the front and it was indeed the front that was the whole cause of the lean, once it was adjusted to be level that brought the rear around. What was so puzzling was that the rear was out a lot further than the front and its never made sense how that was physically possible but there it was. I suspect because I had the heavy factory torsion bars on that half ton and they came with wimpy rear springs, that may have allowed for the rear to react so much to the front end lean. 

[Capt Bob]

Late on this but…

Running 60 psi in the front tires and 65 psi in the rear, the front measures 40-3/4” on both wheels.  (20” OEM tires)

The back measures 41-1/2 on the RR and 41-3/4” on the LR.

Point?……… It’s pretty damn flat side to side.

[Homer1959]

26 minutes ago, Capt Bob said:

Late on this but…

Running 60 psi in the front tires and 65 psi in the rear, the front measures 40-3/4” on both wheels.  (20” OEM tires)

The back measures 41-1/2 on the RR and 41-3/4” on the LR.

Point?……… It’s pretty damn flat side to side.

Well, I wish mine were like that, but it's not. Despite the fact that they put the truck on an alignment pit, it still looks higher on the right side to me. They sent me a picture of the truck on their ramp with a 3-foot bubble level on the rear bumper, and the bubble is dead center, so it must be an illusion, lol. Anyway, it's documented, and I have no drivability issues, so it is what it is. My tape measure must have been made in China since the front is dead on GM spec, as is the left rear. My only discrepancy is the rear right side being higher. That must be the Chevy lean I've read about on various sites. Thanks for sharing your measurements.

[Chuck FB]

1 hour ago, Capt Bob said:

Late on this but…

Running 60 psi in the front tires and 65 psi in the rear, the front measures 40-3/4” on both wheels.  (20” OEM tires)

The back measures 41-1/2 on the RR and 41-3/4” on the LR.

Point?……… It’s pretty damn flat side to side.

As the saying goes, your golden !. Nice that someone in the factory got the front level and the rear happens to fall within what is no doubt a decent factory tolerance. As you probably read my comments of my own truck, someone was too quick or cross eyed in adjusting my torsion bars but at least a very easy remedy and once I did that I was very satisfied with the outcome. I never said one word to the dealership about what I had found or then had done, I knew it needed the "steer ahead" adjusted and the other numbers they generated were fine so all was good in the end. Of course I only caught the issue because of my past experience and measured this one and realized it was out, it didn't just jump out at me as it was not enough of a lean to really catch the eye. I've seen some trucks and that is usually an older truck going down the highway that I am following and it just stands out if has a really bad lean, may even be a broken leaf spring in a case like that or the frame/box twisted in an accident. 

[Capt Bob]

23 hours ago, Homer1959 said:

Well, I wish mine were like that, but it's not. Despite the fact that they put the truck on an alignment pit, it still looks higher on the right side to me. They sent me a picture of the truck on their ramp with a 3-foot bubble level on the rear bumper, and the bubble is dead center, so it must be an illusion, lol. Anyway, it's documented, and I have no drivability issues, so it is what it is. My tape measure must have been made in China since the front is dead on GM spec, as is the left rear. My only discrepancy is the rear right side being higher. That must be the Chevy lean I've read about on various sites. Thanks for sharing your measurements.

Funny thing is my 2018 1500 was like that also. Always thought it was my fat ass and the fuel tank. When towing, I leveled it off with the air bags.

[revrnd]

Ive never heard of the Chevy lean but recall reading PV4 magazine (the old timers here may remember it) about the Toyota Land Cruisers having a lean to them.