C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Rear Spring Mounting

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Old Oct 24, 2004 | 10:56 AM
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Default Rear Spring Mounting

My rear spring on my 84 was worn out. I Got a different one from a ZR1 on Ebay, I believe. When I went to mount it with all the spacers and such installed properly, it doesn't snug up to the differential completely. I mean if I tighten the hardware bolts to the diff. carrier cover there is still a small amount of "slop" or movement. I am assuming that when you tighten the bolts it should compress the rubber snug. What should I do?
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Old Oct 24, 2004 | 11:23 AM
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ok, I just measured both springs. The 84 spring with both rubber cushions on it measured 2". The ZR1 spring when measured the same was 1 3/4", so about 1/4" less. I also changed my rear Dana 36 to a lower mileage 89 version. Are the spring mounting brackets different on the later differential because the later sping isn't as thick with the rubber pieces on it. If it is a different bracket maybe I could find one or can you add more shims? I have never seen the rubber cushions for sale anywhere, in rubber or poly. Any ideas?
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Old Oct 24, 2004 | 11:37 AM
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Accordong to my 1984 to 1989 parts book, the bolts and the spring anchor plates, are all the same. There is a variety of spacer thicknesses avalilable, that are used in various combinations for different applications.

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Old Oct 24, 2004 | 11:47 AM
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Are the spring anchor plates the metal things with the 2 dimples in them? So, can I still buy different thickness plates or do I have to make something up? Ecklers and others sell rear springs listed as 84-96. What happens when you buy one of those? Wouldn't you run into the same problem?
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Old Oct 24, 2004 | 11:54 AM
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Could I use 2 spring anchor plates doubled up on each bracket to make up the difference? I have the thinner ones from the ZR1 spring, might just work. Would you double up on the top or bottom of the rubber cushions or does it have to be even?
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Old Oct 24, 2004 | 12:22 PM
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Originally Posted by vsocks
Are the spring anchor plates the metal things with the 2 dimples in them? So, can I still buy different thickness plates or do I have to make something up? Ecklers and others sell rear springs listed as 84-96. What happens when you buy one of those? Wouldn't you run into the same problem?
The illustration in the parts book is actually a drawing. It doesn't show a detail like a dimple. The anchor plate is the item the bolts pass through. A short (M10x1.5x30) bolt at the front and a longer (M10x1.5x105) bolt at the rear. It shows two spacers directly above and two spacers directly below and in contact with the spring. It appears the insulator goes between the top spacer and the batwing. This IS a generic drawing, so your spacers may vary. The service manual goes into even less detail. But the illustration is consistant with the one in the parts book. It pretty much says to simply remove and replace the spacers and insulators. Sorry, I can't answer for Ecklers.

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Old Oct 24, 2004 | 12:33 PM
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Thanks CFI-EFI. The anchor plate is the bracket. There are different thickness spacers. Do I need 2 spacers on top of cushions and 2 on bottom of cushion so it is even? If it doesn't matter I could make it work with what I have. I would use 2 spacers on the bottom and one on the top. What do you think?

Last edited by vsocks; Oct 24, 2004 at 01:30 PM.
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Old Oct 24, 2004 | 06:33 PM
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The illustration shows in order from bottom to top: The anchor plate, two spacers, the spring, two more spacers, and finally, the insulator at the top. The arrangement of the spacer should make NO difference in their stacked thickness. Either you have enough thickness to compress everything, and keep the bolts from bottoming, or you don't. Where you place the spacers COULD affect the leverage on the bolts and the ride height.

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Old Oct 24, 2004 | 08:18 PM
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I think I have it now but one last question. The anchor plate bracket should compress the spring cushions and then touch diff. carrier, correct? If not then I still don't have enough spacers. If there is too much spacer I am afraid that when I tighten down the bolts the bracket may crack. If the bracket is not suppose to touch how much gap should there be?
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Old Oct 24, 2004 | 11:39 PM
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Originally Posted by vsocks
My rear spring on my 84 was worn out. I Got a different one from a ZR1 on Ebay, I believe. When I went to mount it with all the spacers and such installed properly, it doesn't snug up to the differential completely. I mean if I tighten the hardware bolts to the diff. carrier cover there is still a small amount of "slop" or movement. I am assuming that when you tighten the bolts it should compress the rubber snug. What should I do?
The ZR1 spring, as does each different spring, uses a combination of different part # spacers. A shop manual for the year and model of car that the spring was from would tell which #s are needed and how many of each go over and under the spring.
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Old Oct 25, 2004 | 07:22 AM
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I had a similar problem with mine. It snugged up when bolted, but when the weight of the car was on the spring there was about an 1/8 of an inch play. Went to chevy and ordered 2 HD (thicker spacers) cost less than $5 and now all is well.

Check it with the weight on the spring too.
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Old Oct 25, 2004 | 02:58 PM
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Originally Posted by vsocks
I think I have it now but one last question. The anchor plate bracket should compress the spring cushions and then touch diff. carrier, correct? If not then I still don't have enough spacers. If there is too much spacer I am afraid that when I tighten down the bolts the bracket may crack. If the bracket is not suppose to touch how much gap should there be?
I have never replace either of my springs. Therefore I don't really know. "The anchor plate bracket should compress the spring cushions and then touch diff." That sounds right, to me. Too many spacers (or too thick) won't compress the insulator and hold the spring tightly, and too few will put all the load on the bolts. The '84 service manual does not address spacer selection. It merely acknowledges their existence by showing them i the illustration.

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