Uneven rear suspension

[Homer1959]

1 minute ago, revrnd said:

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.

google it . that exist  

[Chuck FB]

20 minutes ago, revrnd said:

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.

How much fuel is added to the tank of a pickup in the factory ( I assume the truck is all assembled and ready to fire up before the fuel is added ? ). Put another way, I assume the torsion bars would already have been set and alignment before any fuel weight had been added to the truck although if it was desired to be that precise they could calculate a slight over adjustment of the left torsion bar for future fuel weight. 

 

Pure speculation on my part so you can correct me on this but my assumption has been that the torsion bar adjustment done as they set the front end up relies a lot on the person on that shift who performs that task and the end result on the dealers lot goes back to the person who last touched the key bolts in the factory. 

[revrnd]

41 minutes ago, Chuck FB said:

How much fuel is added to the tank of a pickup in the factory ( I assume the truck is all assembled and ready to fire up before the fuel is added ? ). Put another way, I assume the torsion bars would already have been set and alignment before any fuel weight had been added to the truck although if it was desired to be that precise they could calculate a slight over adjustment of the left torsion bar for future fuel weight. 

 

Pure speculation on my part so you can correct me on this but my assumption has been that the torsion bar adjustment done as they set the front end up relies a lot on the person on that shift who performs that task and the end result on the dealers lot goes back to the person who last touched the key bolts in the factory. 

You are correct, the torsion bars (@ least back in the GMT400 days) were set a about 15 or 20 minutes before gas fill. We were building 60 jobs per hour, so each operator has a minute to do their job on each truck.

 

That being said, I think it would be possible to fill a truck off line & then adjust the bars so that tge truck was level. Take what was found and apply it to the specs for adjustment. From my memory and we're going back to 1988, the adjustment fixture was symmetrical from side to side.

 

As Ive said elsewhere, I dont recall seeing a similar fixture  being used on 'the flat top' conveyor during the GMT800 or GMT900 model runs. Maybe it was adjusted in the Chassis Area after the front suspension is fully assembled? I didnt have much to do w/ that area, so I cant say anything certain about the later assembly procedures.

Edited September 12, 2025 by revrnd

[revrnd]

That all being said, I wonder if there is anyone after all these years from Oshawa or Ft Wayne that would know of the fixture Im talking about. Pontiac would've been using it as well.

 

The tools came in from 'Central Office' & were junk. Our tooling department reworked them & the revisions were adopted across the board.

[Pryme]

I just filled up my truck last night and after reading new theories in this thread I went out and measured. Still 41 1/4” both sides. 
 

it’s not even logical to think a full tank of fuel would make any noticeable difference in a truck with a payload of 3,500+ pounds. 
 

If a guys truck is off by 1.5” there is a problem. Period. And any talk to the contrary from the dealer is them selling you a line. 

[revrnd]

W/ this issue, is it always a case of 1 particular side being taller? Or can it be either?

 

Im wondering if it varies, the error, may be like the weight screws on the previous generation of cars that NASCAR raced. Crank 1 side on the rear the affect change on the opposite side in the front.

 

In this situation cranking the torsion adjuster too much on 1 side affects the opposite rear corner.

Edited September 12, 2025 by revrnd

[Homer1959]

6 hours ago, Pryme said:

I just filled up my truck last night and after reading new theories in this thread I went out and measured. Still 41 1/4” both sides. 
 

it’s not even logical to think a full tank of fuel would make any noticeable difference in a truck with a payload of 3,500+ pounds. 
 

If a guys truck is off by 1.5” there is a problem. Period. And any talk to the contrary from the dealer is them selling you a line. 

1 1/2 is my mistake , but its definitly 1 inches ... the spec call for 42 + - 1/2 inches ... so Im really close to be level, the l/s is dead on 42 ... the other side 43 ... Im ok with that .... I prefer that then seeing them playing shimming or Gods know what, i have no drivability issue so all is good  

[Chuck FB]

6 minutes ago, Homer1959 said:

1 1/2 is my mistake , but its definitly 1 inches ... the spec call for 42 + - 1/2 inches ... so Im really close to be level, the l/s is dead on 42 ... the other side 43 ... Im ok with that .... I prefer that then seeing them playing shimming or Gods know what, i have no drivability issue so all is good  

So in the times that you have measured, has the front stayed constantly the same left vs right ? 

 

Also and this may sound odd but is the area your parking on actually level, an example would be a cement floor in a garage that was built with a gentle multi profiled slope that allowed water to make its way to a drain etc, or its an outdoor pad that was poured in a few sections and not actually level across the board. Not saying that is the situation with where your truck is parked and measuring but if a surface has a contour that allows for opposite tires of each axle to be higher that would cause those corners to carry more of the vehicles weight and the other two tires diagonally less. In fact in a lot of commercial shops that are set up to run to gutter drains, there isn't a flat spot to be had in a shop designed like that. Anyway thought I would pass that by you in case you ever felt like measuring the truck in another location and drive yourself batty in the process LOL. 

[Homer1959]

1 minute ago, Chuck FB said:

So in the times that you have measured, has the front stayed constantly the same left vs right ? 

 

Also and this may sound odd but is the area your parking on actually level, an example would be a cement floor in a garage that was built with a gentle multi profiled slope that allowed water to make its way to a drain etc, or its an outdoor pad that was poured in a few sections and not actually level across the board. Not saying that is the situation with where your truck is parked and measuring but if a surface has a contour that allows for opposite tires of each axle to be higher that would cause those corners to carry more of the vehicles weight and the other two tires diagonally less. In fact in a lot of commercial shops that are set up to run to gutter drains, there isn't a flat spot to be had in a shop designed like that. Anyway thought I would pass that by you in case you ever felt like measuring the truck in another location and drive yourself batty in the process LOL. 

You nailed it I realized that my freshly paved driveway have all kind off mini slope to evacuate the rain toward ditch . My measurement were somewhat consistent since I was parking the truck almost at the same place everytime. We are going on a trip next week and I will have the chance to stop on a scale, here we have acces for free outside the spring season or during a surprise inspection for trucker. A scale should be perfectly level so Ill have the final verdict. So far the pictures sent by my dealer with the truck on the alignment pit are telling me that the truck is within gm spec .... 42 + - 1/2 

[Chuck FB]

Do keep in mind if you measure a vehicle with items in the box and lets just say heavy items are all to one side vs centered from side to side and also would apply to items in the cab as well as people biased to one side or the other. Of course it takes more to affect an HD truck over a half ton or a car/small suv. More than likely some large stores huge parking lot would have a fairly level parking lot in areas of it as long as its not near a storm sewer .... and as I grin, I wonder if this struggle does indeed prove that the earth is round rather than flat 

[rjgvt]

@Homer1959

 

If you park in the same spot on your driveway, take your measurements then turn your truck around 180 degrees and measure again. Take the average and see if they are in spec. It should eliminate any variations in your driveway.

 

I haven’t measured my truck but will do if I remember. I have a lot of stuff in my truck and in the bed. Not sure if I have everything evened out. 
 

I did measure the top opening of the hitch opening the other night before and after loading eight 50 pound bags of gravel at the very back of the bed. Truck squatted 3/4”.

Edited September 13, 2025 by rjgvt

[Chuck FB]

14 minutes ago, rjgvt said:

@Homer1959

 

If you park in the same spot on your driveway, take your measurements then turn your truck around 180 degrees and measure again. Take the average and see if they are in spec.

That's a good point, I've done that myself in the past and used chalk to mark the cement in the first parked location and turned the vehicle around. I've also used a transit level to check the surface variables in marked off locations and used shims under the tires if I wanted to be precise ( this gets into checking and shimming drive axles for ujoint driveline angles on a highway tractor etc ). 

Edited September 13, 2025 by Chuck FB