Rear suspension question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

grschell · 07-27-2019, 04:18 PM

I just replaced my factory rear coil spring on the 70 GMC. I decided to go with Touring Tech 4” lowering springs. I also installed shock relocators. After I finished, the drivers side was 1/2” lower than the passenger side. So, I swapped the springs thinking that one spring was a bit softer. Ended up with the same 1/2” difference. So, maybe a bent trailing arm. I was thinking about putting a 1/2” plate between the spring and the frame. Has anyone done this? Or, maybe go with a 1/2” drop block on the pass side?

Also, I was thinking about going with a coil over shock to help with ride height. Is there a good kit to use that is not pricey? QA1s would be ideal, but they cost a pretty penny. Thoughts? Suggestions? Thanks!
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**Ironangel** · 07-28-2019, 05:32 AM

Need to look at your front springs...I had the same issue in one of my 72's and came to find that 1/2 of a coil was broken off in the left side lower control arm pocket. You should be able to eye ball down the frame rails to see any bends or deflections, same with the trailing arms, they should be straight except where the U-bolts attach and at the forward bushings...

grschell · 07-28-2019, 12:46 PM

Great suggestion. I did get 3” drop springs for the front too.. I am going to replace the ball joints, control arm bushings, and bearings while it is apart. I’ll hold off on measurements until I get that done. I just figured that it was something in the rear since I was measuring from the ground up to the frame just aft of the differential. Anyway, I did see a set of coil over “load adjust” shocks that fit this model. Not adjustable but would add some stiffness. Might try them out.
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**kwmech** · 07-28-2019, 12:49 PM

Do not rely on shock mounts to support vehicle weight

**Mbeef61** · 07-28-2019, 01:42 PM

Was it even before the install? Twisted frames also present that way

grschell · 07-28-2019, 03:45 PM

Not looking to support the weight with shocks, but I’m a big guy so trying to keep the ride height with me in it close to where it’s at empty.

As far as where it was at before, the previous owner lowered it by heating the factory coils. Very poor job at that. It was nowhere near level and there was no way to get a good measurement. My plan is to do the front, then measure everything.
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07-27-2019, 04:18 PM	#1
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Rear suspension question I just replaced my factory rear coil spring on the 70 GMC. I decided to go with Touring Tech 4” lowering springs. I also installed shock relocators. After I finished, the drivers side was 1/2” lower than the passenger side. So, I swapped the springs thinking that one spring was a bit softer. Ended up with the same 1/2” difference. So, maybe a bent trailing arm. I was thinking about putting a 1/2” plate between the spring and the frame. Has anyone done this? Or, maybe go with a 1/2” drop block on the pass side? Also, I was thinking about going with a coil over shock to help with ride height. Is there a good kit to use that is not pricey? QA1s would be ideal, but they cost a pretty penny. Thoughts? Suggestions? Thanks! Posted via Mobile Device

07-28-2019, 05:32 AM	#2
Ironangel Senior Member Join Date: Feb 2010 Location: Falls City, Nebraska "100 Miles From Nowhere" Posts: 2,219	Re: Rear suspension question Need to look at your front springs...I had the same issue in one of my 72's and came to find that 1/2 of a coil was broken off in the left side lower control arm pocket. You should be able to eye ball down the frame rails to see any bends or deflections, same with the trailing arms, they should be straight except where the U-bolts attach and at the forward bushings... __________________ Michael of the clan Hill, "Two Seventy Two's" 71 1-ton Dually 350 4-Speed 71 C/50 Grain Truck, 350 Split-Axle 4-Speed 02 3/4 ton Express 14 Indian Chief Vintage 1952 Ford 8N, "Only Ford Allowed On The Property" "Be American, Buy American"

07-28-2019, 12:49 PM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,382	Re: Rear suspension question Do not rely on shock mounts to support vehicle weight

07-28-2019, 01:42 PM	#5
Mbeef61 Senior Member Join Date: Jun 2009 Location: Portland - OR Posts: 242	Re: Rear suspension question Was it even before the install? Twisted frames also present that way

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07-28-2019, 12:46 PM	#3
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Great suggestion. I did get 3” drop springs for the front too.. I am going to replace the ball joints, control arm bushings, and bearings while it is apart. I’ll hold off on measurements until I get that done. I just figured that it was something in the rear since I was measuring from the ground up to the frame just aft of the differential. Anyway, I did see a set of coil over “load adjust” shocks that fit this model. Not adjustable but would add some stiffness. Might try them out. Posted via Mobile Device

07-28-2019, 03:45 PM	#6
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Not looking to support the weight with shocks, but I’m a big guy so trying to keep the ride height with me in it close to where it’s at empty. As far as where it was at before, the previous owner lowered it by heating the factory coils. Very poor job at that. It was nowhere near level and there was no way to get a good measurement. My plan is to do the front, then measure everything. Posted via Mobile Device



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