In the past, I have read that vette composite leaf springs don’t fail, (or at least from fatigue), that aside, my street driven 85 coupe has a failing rear leaf spring. I have had it about 1 ½ years and it has 52K miles on it. It hasn’t seen tough duty. The failure has come on in the past few months as I had the wheels off maybe 2 months ago when I was upgrading the brakes, and I would have noticed it then if it would have been visible.

I was surprised and pleased with the ride as I had always heard about the buckboard like ride of a vette, but I thought mine was good. So my question is; as I want to retain the ride (and so I assume the 39.9 N/mm spring rate), are there real differences between the springs offered by GM and the aftermarket? What might they be? Changing it looks pretty straight forward, but has anyone done this in the past and may have something to pass on to those that are doing it the first time?

I guess my priorities for spring choice would be: 1- ride quality, 2- bulletproof (figure of speech), 3- reasonable cost.
Thanks,
Dave

 

In order retain the existing ride quality check your service parts ID label under the rear compartment lid. Here, you will be able to determine if you have Z51 or the base suspension (I don't know the code off-hand, but it's either Z51 or not). That will determine which spring to purchase. GM may or may not list a seperate spring but aftermarket suppliers will. I think GM only offers the base as replacement.

This is a good time to go with poly bushings. (and if you want to adjust the ride height a bit the lowering kit is pretty cheap)

When you take the bolts out of the spring to diff bracket, you will be greeted with various spacers, note their location so you can reinstall them in the correct pattern.

Have new cotter pins on hand, if yours are 20yrs old they may need to be destroyed to be removed.

Use a jack on the end of the spring you are working on to keep tension on it. Jack up the spring enough that the bolt can be jiggled loosely. Remove the bolt, then slowly release the jack to remove the spring tension.

 

no matter what you choose, i would upgrade your bushings on all 4 corners. the poly ones have made a huge difference in my '84 and i cant say enough good things about them

 

Is there an chance it has been exposed to chemicals, heat or
mechanical damage (notched by a jack or ?)

Heat can lead to trouble: Track Carnage - Anyone heard this one before?

You should be able to easily find a good used 39.9 spring in
C4 Parts, Autocross & RR or from forum used parts vendors like Vette2Vette.
Between cars being parted out and others that have been modified, the
39.9 spring will be widely available.If you are satisfied with the current
ride rate, then my vote is that a good equivalent will restore this, no
matter what the source of the spring.

Where VB&P really shine is at making a selection of higher-than-OEM
-rate composite springs available. If you happened to want to increase
the rate of your spring, I'd recommend VB&P's products and service
in a heartbeat.

A rear spring change is a straightforward task. A hoist is nice but
regular height jackstands are sufficient. A means of supporting the
spring on the metal ends as the bolts near disengagement is
required but easy to juryrig. The key is not to mark the composite
material.

Measure from the ground to the rocker panel before starting to
baseline the current ride height. There are factory-recommended
locations, perhaps someone can offer these. Use the jacking arrows
in the absence of any suggestions, (I feel any point along the ends
of the rocker is adequate as long as it is used consistently before/after.)

When removing the existing spring, take care to note the position
of the existing pieces on top and underneath the spring where it
is fastened to the batwing. These help establish ride height.

Something to order to have on hand are the rubber bushings for
the bolts that tension the spring. These are available from
GM as #10262518 - INSULATOR, SPR



.

 

I read that wheel cleaners have chemicals that attack the fiberglass springs. That's why I don't use them.
did u use them? and if u did, for how many years?
just curious

 

After reading your responses and a couple of others that I found on the forum, it finely soaked in what I had done to screw the spring up. About a month ago I took the Vette on a long and rainy road trip. It was filthy when I got home and about a week later I couldn't stand it any longer, but it was too cold to wash it in the driveway. So, I drove it through one of those drive thru car washes where you drive over the block and it pulls the car through. I heard a thump as I pulled on but everything seemed OK. On the way home the muffler on the drivers side came off the pipe and just hung there by the hanger. I only live 2 or 3 miles from the carwash but I guess that was far enough.

To all that offered info and help, thanks.
Dave

 

wait,
1. your muffler popped off and u didn't notice the difference in the noise?
2. you didn't actually look at the spring, you just associated the noise at the back of the car to be a spring?
3. the car didn't sit low at one rear corner, and you still thought it was a spring?

sheesh

 

WAIT FOR WHAT?
1. Windows up, radio on, low speed through city streets, traffic, so the first thing I noticed was that the exhaust resonance may have been less. I was still trying to figure out if it really did get quieter, but by that time I was home.
2. When I pulled in the garage I did check under the car and saw that the muffler was hanging loose but didn't see the spring damage at that time. The car sat in the garage for over a week before I got around to fixing the muffler.
3. As the spring still isn't completely failed, it still doesn't sit any lower. I first saw the spring damage a couple of days ago when I jacked it up to get under it to put the muffler back on. There is no doubt, the spring is failing, (not failed, but failing).

By your tone you obviously find yourself terribly clever and think it makes you look even more so by trying to throw rocks at others. Sorry to burst your little bubble but it always works the other way. Sheesh!

Dave

 

Cheap shot!