My C-3 Squats!

[Greg A.]

I've been spending more time with other C-3 owners lately and really notice that my '78 squats low in the rear. The distance from ground to top of rear wheel well is 27 inches and 30+ inches in the front.

I had the rear spring replaced (supposed to be with stock replacement -- GM or ?) with much of the rear suspension 2 years ago. Is it possible that the rear spring bolts are too short? I noticed in the AIM that there were alternate bolts to level the ride height. Will this compress the spring too much and cause the lower ride height. Handling is fine and I don't notice it until I'm parked next to another C-3 and mine looks like it's launching or taking a d**p.

Plan to take it back to the shop that did the work but hope to have some idea of what might be wrong...Appreciate the comments!

Greg.

[Wayne W.]

Re: My C-3 Squats!

Bolts too long, shorten them to raise the rear. I am assuming you have the steel spring. Look at the spring. It should have a slight bow absolutely no less than straight. If so check the rubber pads on each end of the bolts. They will get compressed. If you do not want to change the spring the height can be raised by shorter bolts or spacers unter the lower pad.

[Duke W.]

Spring Cushions

Did you replace the four rubber spring cushions when you replaced the spring? These compress over time which causes the rear to lose ride height. They should be replaced about every five years even if the car isn't driven. New cushions will also significantly reduce ride harshness. If the cushions are fresh then I would have to suspect that the spring is incorrect or the spring link bolts are not the correct length.

Duke

[Robert C.]

Re: Spring Cushions

Greg, You didn't forget to tell us that you replaced the front springs as well! That is usually the problem. New front springs will generally throw the whole car out of line.

[Joe L.]

Re: My C-3 Squats!

Greg-----

If you choose to use spacers (at least to see where it gets you), you can use additional GM #3831587 "retainers". These are the larger washer-like piece which underlies the rubber spring bolt cushions. You can stack them up as necessary to, effectively, shorten the spring bolt. They're still available and GM List for $1.93/each. You could also use large washers from a hardware store, but I doubt that you'll find such a large washer with an appropriate center hole size.

[Greg A.]

Re: Spring Cushions

Negative on changing the front springs, Bob. I did get 4 new KYB shocks all around and front inner tie rods, but the front springs are original. I'll have to look at the spring again tomorrow to check the bow...I believe there is very little. Both sides received new bolts, and rubber pads, and it is a steel spring, with the correct # of leaves (9 I think)...does not have FE7 Gymkana.

Does 29.5 - 30 inches seem a lot for the front dimensions of ground to top of inner wheel well (at center line?) I assumed this was high because the rear was low. The only dimension I found in the AIM is from just under the rocker panel to ground both behind the front wheel and in front of the rear. Based on this measurement, the rear is about 2 inches low.

Thanks for the advice...any more ideas?

Greg.

[Duke W.]

New bolts?

The shank length of the original spring link bolts on my SWC is about 6.25 inches, but I'm not sure if different bolts were used in other model years. Is it possible that you have the wrong bolts? Also, are the washers and grommet retainers correct?

Duke

[Chuck S.]

Re: New bolts?

Duke,

Yep, some of them are shorter. Maybe the later model C3s. I got some by accident at Bloomington's swap. Right head stamp, waay too short; seem to recall about 1.5".

Chuck Sangerhausen

[Wayne M.]

Re: New Spring Link bolts?

My rear spring is out for a diff change (early '65); just measured the bolts and confirm Duke's dimensions --- 6.25" exactly from under the bolt head to the tip. Car sits at perfect (factory) height.

[Duke W.]

Re: New bolts?

I figured the C3 might have shorter bolts, which would raise the ride height on C2s or restore proper right height on the heavier late C3s. Greg might have early C2 bolts. My 9/77 rev of the parts catalog calls for a 351592 spring link bolt for 75-78 (Group 7.529). No listing for earlier models, so it must be a different bolt that was discontinued - maybe longer, eh? Greg - make sure you've got the correct spring link bolt for your year! Maybe Joe can confirm the proper p/n and shank length.

Duke

[Chuck S.]

Re: New bolts?

Duke,

Joe Lucia must be taking the night off; this is his meat and potatoes.

I must have misunderstood which bolts you are talking about; Grp 7.529 is the bolt that passes through the clamp plate, mounting the spring to the differential housing. Length in that instance only has to be long enough to pass through the clamp plate, past the spring, and into the differential housing with sufficient length to provide full strength. They are fairly long, but their length will have no effect on ride height.

The bolt I thought you were talking about is the spring hanger bolt, Grp 7.506, Part No. 3831585 (My catalog groups it with the spring center bolt which is obviously incorrect). This bolt is the same for '63 up to at least '72 (last year of my parts catalog), and measures (as posted) 6.25" in length from bottom of the head with a 9/16"-18 threaded end. The bolts I bought at Bloomington had the same head stamp and same reduced cross-section shank configuration with a cotter pin hole in the end, and were about 1"-1.5" shorter. I looked for the little imposters just now to measure them, but I can't find them. I thought they probably were implemented when they changed the differential to aluminum in the late C3s. Did they use a fiberglass spring with that set-up?

If GregA. has mistakenly installed the longer bolt (6.25") instead of the shorter bolt I bought, that would make his ride height lower, right? Maybe I can swap him these shorter ones for the 6.25" bolts

Chuck Sangerhausen

[Chuck S.]

Edit: Alum Differential & Monoleaf Spring

Duke,

Just found it! Aluminum differential first introduced with '80 model year, fiberglass monoleaf spring with '81 model year.

Another "theory" bites the dust, but man, am I gettin' smarter!

Chuck Sangerhausen

[Duke W.]

Re: New bolts?

Chuck - I looked at the IPB sheet (2/77) and it refered me to Gr. 7.529, which contained the "BOLT rear spring", 75-78, p/n that I quoted. The same group also had a listing for BOLT rear spring plate. So, based on your note I look at Gr 7.509 and I find a listing: 63-75 Bolt rear, 351592, which is the same p/n as the listing in 7.529 for 75-78, but DIFFERENT than listed in your '72 book. I just love these wonderful GM parts catalogs. Sounds like those on the ball GM guys just substituted the late bolt for the early bolt eventhough it is probably SHORTER, which would RAISE a early (lighter) car. My suggestion is that you should start a new thread about the spring link bolts for C2s and C3s. I figure that there were two and the late one (shorter?) was subsituted for the early 6.25 inch long bolt,even though it was wrong. I suspect the early bolt is available through the repro channel, and maybe GM still services the late bolt, but, like you say, this is Joe's stock in trade. My suggestion is to start a new thread, so Joe will pick up on it next time he logs on.

Duke

Duke

Duke

[Greg A.]

Re: My C-3 Squats!

My thanks to all of you for the comments/suggestions. I took a good look at the spring and bolts, etc this morning and think I may know what some of the problem is. Carefully counting the spring leaves, I find it is actually just a 7 leaf spring. No FE7 on this car (no rear anti-sway bar), so I believe it should have been replaced with a 9 leaf spring. I'm not sure how this would alter the ride height, but I know it's not the correct replacement spring.

Wayne mentioned bow in the spring. It has a slight bow "up" (ends curve up slightly.) Is this the proper direction of bow? Spring bolts are 6.25" long which appears to be the standard.

Next week, I'll take it back to the shop that did the spring replacement and question the use of the current spring.

I have some photos for anyone interested...again, thanks for the assistance.

Greg

[Duke W.]

Re: My C-3 Squats!

Problems with repro and even GM replacement parts seems to be a recurring theme on the Board, and the rear spring is one of them. Base suspension cars have a nine leaf spring and the various HD suspensions over the years have a seven leaf rear spring. Spring problems have been discussed, and I do not subscribe to the theory that springs "wear out". I just doesn't jibe with my materials science knowledge (which could be lacking), but I do believe that springs loose their rate and restoring force because of loss of material due to corrosion.

My suggestion is to disassemble your original spring, clean it thoroughly of corrosion, and if it does not appear to have lost a significant amount or its original material, reassemble it with new spring liners and reinstall it. Though the rear spring did not originally have any coating you should consider painting the leaves or otherwise implementing some other process that will slow corrosion.

Many feel that all efforts should be made to rebuild or otherwise restore orignal components before replacing them to maintain both originality and the compontent's original design performance. I agree with this philosphy on both counts.

Duke