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Discussion Starter · #1 ·
Hi All, I'm getting ready to order new leaf packs from sdtrucksprings for my 04 AWD. Factory replacement for this van would be the 3 leaf setup, without the rebound leaf.

Are there any advantages/disadvantages to running the 3+1 leaf pack instead? Why did GM offer both options?

It seems the rebound leaf will help with heavier loads, so I'm leaning in that direction, but some clarification would certainly be helpful.

I also have new leaf plates on the way with u bolts to do away with the clamshells.

Thanks in advance!
 

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The 3+1 will raise the rear of the van quite a bit, I can't tell you how much because I had glass springs (1st gen) and swapped to steel using all the parts from a 2000 in the salvage yard then bought the 3+1 set your speaking of. To bad you already bought the parts to do away with the clamshell set up as I have all the parts but am not using them and would sell them at a good deal.
 

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Discussion Starter · #3 ·
Thanks for the info. Guessing the lift will equate to the difference in thickness in the leaf pack in my case? If that's the case, its only ~1/8" - ~1/4". Either way, I'm going for a 2" lift with adjustable shackles at this point.

It is what it is about the u bolt conversion. I'm sure you can flip them pretty quick in the classified section. I picked up 3/8 thick plates and 5/8 bolts.
 

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My van is an 89 RS with a 98 AWD frame I originally did the steel spring conversion as I said, but after I bought the parts to do away with the clamshells I realized I would not be able to use my factory rear sway bar, so I put brand-new clamshells and grade 8 bolts instead.
 

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Discussion Starter · #5 ·
Update:

Based on some of the reading I've done, it seems that 3+1 configuration includes a rebound spring, which is described interchangeably as a overload spring, or as a helper spring.

Being shorter, and thicker, it acts as a 2nd stage in leaf pack compression, with it's primary purpose to help maintain ride height under heavier loads. It's commonly used in cargo vans (with leafs) or trucks and shouldn't behave any differently than the 3 leaf pack until that 2nd stage is engaged. I'm guessing GM didn't use a 3+1 for a passenger spec van for the obvious, as well as cost savings during manufacturing?

With that said, I'm going with the 3+1 (sdtruckspings part 22-1195 instead of 22-1259) for the following reasons:
  • I remove the seats for hauling once in a while.
  • Already swapping the clamshells to ubolts with leaf plates, so there will be no fitment issue with the thicker pack.
  • The 3+1 is actually cheaper to replace that the 3 leaf pack.
 

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Discussion Starter · #7 ·
I was wondering about those HD springs as well, paired with a swaybar. Are you permanently loaded down in your van? I think they may be overkill for me. It would be great to have the luxury of trying different setups to dial in one's preference :)
 

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No, my van is converted, interior mods probably weigh about what the seats did. The ride on the 22-1195hd is not harsh, I drive mountain roads regularly and it handles well with my 2” lift and no rear sway bar.
 
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