C4 rear end adjustment

[Bow tie downunder]

Is it possible to adjust the body height.I’m after 1/2 to 1 inch increase in height.

[55 Rescue Dog]

If you are running the composite transverse leaf spring like I do, you can simply use shorter bolt on the ends of the spring or add spacers between the nut and the bottom end of the spring. You can only raise it up so far before interference. If that's not enough, then you would need to find a stiffer spring. They had several different ones on the C4's but I have no idea which one would be best. The other thing is to shed a little weight in the rear. I don't have spare, and my battery is not in the trunk. I don't fill my 22-gallon tank either. My car is pretty stripped down at 3400lbs, but it rides and drives perfect with plenty of suspension travel. Which C4 conversion frame do you have? On the front you would need to maybe add spacers to the ends of the spring, which is more difficult. Beautiful car btw.
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[Bow tie downunder]

Thanks for your help .I have raised the front on the coilovers which has made the car sit level.I don’t want to upset the geometry .I thought of using 20 inch wheels instead of 18 .

[WagonCrazy]

That's going to take a coil over adjustment (probably loosening the ring below the spring so that it relaxes the spring compression.
If you get it all the way loose (springs move around by hand), then you may need to go with the next longer spring length.

[55 Rescue Dog]

I chose not to use coil overs for several reasons, and I kept the weight of my car to near the same as a 96 Corvette running the stock size 275/40-17 tires with 9.5 wide wheels front and rear. It drives perfect like a giant Corvette and sticks to the road like you wouldn't believe.
1955 Chevy autocross - YouTube (https://www.youtube.com/watch?v=L_bJUqqTpdI)

[Bow tie downunder]

12758
Thanks for your help .I have raised the front on the coilovers which has made the car sit level.I don’t want to upset the geometry .I thought of using 20 inch wheels instead of 18 .This is what I have

[55 Rescue Dog]

It looks like you could use a thicker rubber bushing between the end of the spring and the spindle, which would raise it an inch for sure. Bolt looks plenty long too. Otherwise, you need a stiffer spring.

[Bow tie downunder]

Thanks for your input .L have adjusted the front it’s the rear I’m not sure of.

[WagonCrazy]

Oh, now i see. You still have the stock batwing leaf spring set up on the rear.
On my Nomad build, I eliminated that batwing in favor of coil overs.
Not sure how to advise you on height adjustments with your setup.
Possibly swap out the fixed length link shafts at the end of each leaf spring? Maybe a longer one would raise the ride height? Thinking out loud here...no experience with it though.

[BamaNomad]

Thanks for your input .L have adjusted the front it’s the rear I’m not sure of.

With the C4 transverse rear spring, rear height is easily adjustable (within limits).

To lower the rear of the car, remove the cotter pin and tighten the large nuts at the ends of the spring. Replace the cotter pins of course afterwards.

To raise the rear of the car, remove the cotter pin and loosen the large nuts at the ends of the spring. You have a lot of room to further raise the rear, and one can even go to a longer bolt as long as the spring is strong enough to further lift the car.

For my curiousity. Would you check the 2-letter code stamped into the spring and let me know which one you have?

[BamaNomad]

Oh, now i see. You still have the stock batwing leaf spring set up on the rear.
On my Nomad build, I eliminated that batwing in favor of coil overs.
Not sure how to advise you on height adjustments with your setup.
Possibly swap out the fixed length link shafts at the end of each leaf spring? Maybe a longer one would raise the ride height? Thinking out loud here...no experience with it though.

This is just 'semantics', but Paul the 'batwing' is the Aluminum Component that holds the differential and allows retention into the chassis. The stock rear C4 spring is a single transverse composite spring, clamped in the middle and which uses the ends of the spring to suspend the wheels/tires.

PS. I went with the original rear suspension as well for two reasons: 1) to retain stock GM components as much as possible for future replacement purposes, and 2) I do not plan to drag race my Nomad, and one additional reason: I dislike coil over suspensions!

[55 Rescue Dog]

Actually, to raise the car you need to shorten the bolts that the end of the spring that is suspended from the spindle, which applies more pressure to the center mount of the spring mounted below the diff, which raises the car. To lower the car, you use longer bolts on the ends of the spring. Opposite of what it appears to look like. Same spring setup on the C3. C5, C6, and C7 Corvettes.

[Bow tie downunder]

Sorry for the late reply and thanks for your help .The car is lower on one side about 1inch .13349

[chevynut]

Sorry for the late reply and thanks for your help .The car is lower on one side about 1inch .

Looks like it's only been about 7 months. :-D

Are you sure the problem is in the rear? Does the front sit level?

I noticed you're not using a dropped toe adjuster. Did you notch the frame to clear the stock one? The frame in that area is already weak and notching it could have made the frame low at the right rear corner.

With the car sitting on level ground, measure the front end to see if it's level. If it's not, it could still be a rearend problem. Put a floor jack under the differential and raise the rear off the floor to see if the front end sits level then. If it doesn't, adjust the front coilovers. If it does, the problem is in the rear.

Measure from the spring straight up to the end of the batwing on both sides. That measurement should be the same if the car is level. Are both spring bolts adjusted the same? Tightening the nut (shortening the bolt) will raise the car, and loosening it will lower it.

Car looks great btw.

[Bow tie downunder]

Thanks for the advice .Inreplaced the tyres on the rear with 265x45 18 which gave me an extra 1inch of clearance.The rear was too low with a 35 profile .The front is level.The measurement at the batwing is 92 mm and 95 mm.The spring bolts are the same on bothe ends .The only thing I can see that is different is position of the camber adjustment.
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[Bow tie downunder]

Can you supply the dropped toe adjuster ,they are not on eBay .I had 50mm clearance but now It is 40 mm.

[55 Rescue Dog]

From the picture of the back of the car it looks like too much negative camber on the right rear.

[Custer55]

To raise the ride height you need shorter bolts or spacers as RD55 stated. To lower the ride you need longer bolts as I did on mine. Ride height can be fine tuned within the range of the threads on the bolts.

[Bow tie downunder]

Thanks That’s how I see it.I had the rear end aligned professionally.[ATTACH]13354

[Bow tie downunder]

Thanks for your help ,I only need to raise one side by 7/8

[chevynut]

The front is level.The measurement at the batwing is 92 mm and 95 mm.The spring bolts are the same on bothe ends .The only thing I can see that is different is position of the camber adjustment.

Where are you measuring the height that's off? At the bumper or at the rear wheelwell?

What are the 92mm and 95mm measurements? Is that right (92) and left (95) from spring to batwing?

If the front is level and the back is not, it seems like there's something wrong with the frame. I don't see how the front can be level if the back isn't, unless the frame is twisting or one of the the rear corners is too high or low. I have seen that happen when we welded the batwing mounts and axle bumpers to the frame at the rear hump. We have had to correct that in the past. If the problem is the suspension, and the right rear is low, I would expect the left front to be higher than the right front.

I would try to set the frame perfectly level just forward of the rear wheels at the bottom of the hump, then measure from the floor to the bottom of the frame just forward of the rear bumper on both sides to see if the frame is twisted or sagging on one corner. You could put the frame on exactly the same size blocks to level it.

I don't understand your comment about the camber adjustment. What you're showing in the pic is the toe adjuster so I assume that's what you mean. I don't see anything wrong there.

There are supposed to be shims between the spring and the differential. Are they the same thickness on both sides? It wouldn't take much difference to cant the spring at the end.

[chevynut]

Can you supply the dropped toe adjuster ,they are not on eBay

I can't but I know who can. He's been making them for quite a while, so I never did. I'll PM the info.

[Bow tie downunder]

13356I’m measuring at the rear wheel well through the centre of the wheel. From the back of the car the right hand side is lower than the left. The right hand side is 92mm from the batwing to the spring. The front is level with Coilover adjustment. From the back the left front is adjusted to make the front of the car level 13355

[chevynut]

It looks to me like your driver's side coilover is adjusted quite a bit higher than the passenger side. Looks like it's at least 3 turns higher. Where are you measuring the front end for level? See if the frame is actually level in front.

[Bow tie downunder]

Thanks

[Bow tie downunder]

Thanks
I’m considering coilovers .Could you recommend a spring rate and shocks .

[Bow tie downunder]

Thanks
The numbers on the spring are RHZ
1-6

[chevynut]

I’m considering coilovers .Could you recommend a spring rate and shocks .

I'm not sure coilovers are the key to solving the root cause of your leaning problem. As I mentioned, the front coilovers are not adjusted the same so there's something going on with your chassis/suspension and I'd be inclined to find the root cause before trying to bandaid it. I'd measure the length of each front shock to see if they are the same length at ride height. Your left front shock is adjusted higher and if the shock is actually longer eye to eye than the right side, that would explain why your right rear is low.

To install coilovers you would have to have a shock bar in the rear. I don't like trying to mount the rear shocks vertically like in the C4 Corvettes and some conversions I've seen. The shocks need to be very short and there's just no room for them in the rear unless the top of the shock is inboard. I can't recommend shocks or spring rates without knowing the length between the mounting points at your desired ride height. What is your front coilover spring rate?

[Bow tie downunder]

12 CS 350 on the front