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Old 01-30-2012, 10:16 AM   #1
MAC71
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C20 Burb Rear Springs

I have a spring issue that I am looking for some thoughts on. This is a 72 C20 Suburban with big block and a dana 60. When I bought the Suburban about 7 years age it had a rather smooth even ride. Shortly after getting it I jacked it up and discovered that both rear springs were broken, as in the differential swung away from the truck and only the shocks and track arm were holding up the differential. I ordered heavy stock height C20 spring set from LMC truck, but with those springs the truck is really bouncy. I have tried 4 different types of shocks. The best shock so far has been some heavy duty Rancho shocks. I then ordered a rear set of springs from year one, but that made it even more bouncy. I am now thinking that the springs are to stiff and the shocks just can not control the springs and was thinking of trying some C10 springs. I was wondering if any one had any ideas?
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Old 02-01-2012, 01:11 AM   #2
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Re: C20 Burb Rear Springs

Any one?
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Old 02-01-2012, 01:56 AM   #3
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Re: C20 Burb Rear Springs

If you want to soften the ride in the rear, I doubt going to half ton springs will make an enormous difference. All the original trucks I've ridden in were sprung very stiff, 1/2, 3/4, and 1 ton. I don't have much experience in the coil sprung models, mostly a 4x4 guy myself. I would look into a shackle flip for the rear springs, with a set of longer 64" springs off a newer 3/4 ton truck. You'd get a softer ride with more suspension travel, and maintain the hauling capacity of your suspension.

DIY4X has some nice gear, and they are who I'll use when I get to my shackle flip. OffRoadDesign is another good place that makes custom suspension stuff for our year trucks.
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Old 02-01-2012, 02:28 AM   #4
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Re: C20 Burb Rear Springs

Faithblinded

Thank you for the info. The rear of this truck has coils. Also I have a C10 P/U truck that also has coils and rids really well. No bounce to it. I did try swapping shocks between the 2 trucks but it did not make a difference. I have not tried swapping springs, but I no that would create a new problem on the Suburban which would be the back end would be lower than the front. The crazy part is that with the old broken rusty springs it had a really nice ride.....and had a broken shock mount.
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Old 02-01-2012, 02:58 AM   #5
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Re: C20 Burb Rear Springs

Oh I didn't realize your C20 Sub was coil sprung in the rear. I have a tendency to think 4x4 since mine is(leaf sprung). I'm not sure what the best way to soften the rear of a coil sprung burb is. There must be some softer springs you can swap in, with a high end adjustable shock, to get a more controlled ride.
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Old 02-01-2012, 03:49 AM   #6
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Re: C20 Burb Rear Springs

But I really don't know if the problem is that I need stiffer springs or softer springs. I am now thinking softer because I have the stiffest 3/4 ton springs I could find. Its not that the back end is to stiff its more like you hit a big bump and it bounces way to much, to the point that it effects the control of the vehicle. Just stuck as to what route to take.
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Old 02-01-2012, 07:09 PM   #7
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Re: C20 Burb Rear Springs

I think a lot of the problem with replacement coil springs is that as time goes on they kinda group more of the vehicles together. When they built the trucks there was probably like 30- 40 different part numbers, Now there`s only 2 or 3 for stock springs. They even group, Suburbans, Panels and Pick-ups with the same part numbers.
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Old 02-01-2012, 08:18 PM   #8
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Re: C20 Burb Rear Springs

I would look at a better shock absorber.
KYB or Bilstein are my favorites.

The KYB gas adjusts I used on a "bouncy" 68 elCamino with new springs, and after putting them in it was a night and day difference.

The Bilstein 5100 series is what I have in my 1970 K10 with leafs, they replaced Rancho shocks and again a night and day difference.
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Old 02-02-2012, 04:38 AM   #9
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Re: C20 Burb Rear Springs

All, Thank you for the ideas.

Street Smart your probably dead on! The "right " spring probably just is not available any more. Now its just a matter of figuring out what will work correctly.
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Old 02-02-2012, 04:48 PM   #10
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Re: C20 Burb Rear Springs

-
There are two different trains of thought here and it depends on what your definition of bounce is. If you go to the rear of the truck and push up & down on the bumper can you "bounce" the rear up and down? If so how far? When you hit a decent size bump in the road does it feel like the rear of the vehicle is leaving the road and becoming airborne? I'm betting the rear springs are too stiff and it has nothing to do with the shocks....

Just my 2˘ worth.

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Old 02-28-2012, 11:06 PM   #11
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Re: C20 Burb Rear Springs

I spoke to Early Classic and emailed photos of how the truck was sitting with the heavy duty springs. The back is about 3 ˝ in higher than the front. They suggested using a standard 2 in drop spring to level it out. Well it dropped almost 6 in making the back 2 in lower than the front. I spoke with early classic again and they are sending a 2nd set of springs that they say will level the truck out. The bounce problem is gone now. Just have to get it to sit level.
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Old 02-29-2012, 04:55 AM   #12
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Re: C20 Burb Rear Springs

When i first did suspension work in my Sub i used Early Classic, quality stuff and very helpful. Let us know how it works out.
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Old 03-21-2012, 07:58 AM   #13
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Re: C20 Burb Rear Springs

A update on the springs. I Installed a pair of standard C-10 springs from Early Classic and the truck sits level and rides really well. It also handles a lot better.

Because the truck sat almost four inches higher in the rear than the front I bought a pair of two inch lowering springs. The two inch lowering springs lowered the back six inches making it two inches lower than the front. I called Early Classic and then sent a standard height spring at now charge, and paid for the shipping to my location and for UPS to pick up the two inch drop springs.
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Old 03-21-2012, 08:45 AM   #14
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Re: C20 Burb Rear Springs

Quote:
Originally Posted by MAC71 View Post
A update on the springs. I Installed a pair of standard C-10 springs from Early Classic and the truck sits level and rides really well. It also handles a lot better.

Because the truck sat almost four inches higher in the rear than the front I bought a pair of two inch lowering springs. The two inch lowering springs lowered the back six inches making it two inches lower than the front. I called Early Classic and then sent a standard height spring at now charge, and paid for the shipping to my location and for UPS to pick up the two inch drop springs.
Of course we need before and after pictures Mike
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Old 03-21-2012, 08:58 AM   #15
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Re: C20 Burb Rear Springs

Ok here are some photos. Sorry there not the best. One is with the heavy duty springs then one with standard springs and one with the 2 in drop springs. The way I have it now is with the standard springs which is the photo that was taken at night with the truck sitting level.
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