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2500HD/3500 HD Trucks & Drivetrain Discussion Forum for the 2001 & newer 2500HD/3500 Trucks, Transmissions & Drivetrain

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  #1  
Old 05-23-2017, 11:50 AM
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Default Springs and torsion bars

So got the truck aligned this morning at a local tire shop (Kal Tire, reasonably well known in BC for being a reputable shop).

They did a great job on the align, pointed out the following:
1) The steering was very tight, but even so there's play in the wheel. This is the steering gear, they said it was a low priority (I'm not worried about this ATM)
2) They pointed out that even with new components the bottom control arm is almost on the bump stop, hence worn torsion bars.
3) They pointed out that it sits nearly on it's overload springs.

Just wondering how often those components need replacing? We tow a 30' 5th wheel that puts about 1400lbs on the bed. So not super surprising. I'm planning on doing another round of maintenance after the summer and will get the torsion bars + springs (if they're needed). Am I safe to tow in this state? We're not going far and it's highway / nice roads the whole way this summer.

Thanks!

Gary Lucas
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Old 05-23-2017, 04:09 PM
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The control arms are supposed to rest on the "bump stops". If they aren't, the torsion bars have been cranked up, or the bump stops are worn or chunked out. They are a consumable item. Torsion bars rarely ever fail. It almost takes a catastrophic event to damage them. The are adjustable.

The rear springs, if not sagging, are likely OK. "Nearly on the overload springs" sounds pretty normal after break-in. If your front end Z-height is correct, it will cause the rear to ride higher on the rear springs. Worn-in springs are far from failed. If one side isn't sagging more than the other, they should be good. I'd tow with it.
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Old 05-23-2017, 10:05 PM
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Quote:
Originally Posted by DmaxMaverick View Post
The control arms are supposed to rest on the "bump stops". If they aren't, the torsion bars have been cranked up, or the bump stops are worn or chunked out. They are a consumable item. Torsion bars rarely ever fail. It almost takes a catastrophic event to damage them. The are adjustable.

The rear springs, if not sagging, are likely OK. "Nearly on the overload springs" sounds pretty normal after break-in. If your front end Z-height is correct, it will cause the rear to ride higher on the rear springs. Worn-in springs are far from failed. If one side isn't sagging more than the other, they should be good. I'd tow with it.
Awesome, thanks!

Both sides are level and I feel better about the whole thing again!

Gary
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Old 06-17-2017, 03:25 PM
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So now I'm eyeballing my truck every time I see it looking for one side higher than the other.

The interesting part is that on level ground it seems level, or at least as close as it possibly could be (at most .5" out driver to passenger).

However when parked on a slant it's not entirely even side to side and obviously looks slanted. IE it's more like 3-4" higher on one side than the other when measuring from the ground on each side. Which is I guess how suspension is supposed to work?

Any additional investigation I can / should do?

Thanks!
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Old 06-18-2017, 07:52 AM
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Spring height concerns should only be addressed when the truck is on a level surface. On an old(er)/worn-in truck, the front end Z-height should only be measured while the rear frame is suspended/supported at a specific height to compensate for worn/worn-in rear springs. Once the front is correct, then the rear can be measured. Do not expect it to remain in a similar appearance when parked on non-level ground. With a relatively high CG (Center of Gravity), it doesn't take much of a gradient to cause load differentials on the suspension, and cargo, fuel and accessory loading can affect that, as well. Simply, on a truck with thousands of miles on it (especially loaded/towing), if it's close, it's likely OK.
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Old 06-18-2017, 12:25 PM
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Quote:
Originally Posted by DmaxMaverick View Post
Spring height concerns should only be addressed when the truck is on a level surface. On an old(er)/worn-in truck, the front end Z-height should only be measured while the rear frame is suspended/supported at a specific height to compensate for worn/worn-in rear springs. Once the front is correct, then the rear can be measured. Do not expect it to remain in a similar appearance when parked on non-level ground. With a relatively high CG (Center of Gravity), it doesn't take much of a gradient to cause load differentials on the suspension, and cargo, fuel and accessory loading can affect that, as well. Simply, on a truck with thousands of miles on it (especially loaded/towing), if it's close, it's likely OK.
Ok, it's probably fine. I'll stop worrying about it. When I have the box off in the fall I'll poke around a bit when I can see everything.

Thanks!
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Old 06-19-2017, 07:08 AM
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Having the box off makes it easier, but not by much. Unload the springs and disconnect a hanger at one end. Measure the arc height and eye distance of both springs. I think you'll find they will be within a fraction of an inch (a few millimeters), which is within the spec. of new springs. This is also a good time to clean/inspect bushings and hardware, and replace as necessary.
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Old 08-20-2017, 01:03 PM
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Back when I first setup Lil Red, my Duramax conversion truck, I noticed that one side up front was not at the exact same height as the other side. I used the torsion bar adjustment bolts to make the right/left heights equal. This also made the rear of the truck equal in height side to side. So, upfront side to side torsion bar leveling has an effect on the rear of the truck too.
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