First of all, my apologies if this has been discussed here before. I've searched both using google and the forum search function, but I have not been able to find any info on this.

I have a 1985 C4 front and rear suspension that is going into a project car of mine and I need to remove the leaf spring from the front suspension and convert it to coilovers. It's going into a much lighter car and I will have no control over the spring rate or ride height with the stock leaf spring design.

Everywhere I look, the advice seems to be to get the car on jack stands and use the weight of the car and a floor jack to compress the spring. In my case, that's not an option. What's the best way to do it with the suspension out of the car, safely and without damaging anything?

 

I know what you need there's a special tool I believe made by OTC to cage the spring and all Chevy dealer should have it (I'm sure lost or broken by now) I had hanging on my wall at the dealership. I was using it non stop in the early C4 years when people where bitching my car is to low or rides to hard. Get rid of the Z51 spring.
I will keep trying to find a picture of it

 

Something like in the picture below? I found a tool by Kent Moore. It could be an option, if it was possible to rent one here in Sweden somehow. Paying $6-700 plus shipping and customs from USA just to remove the spring is not an option I'm afraid.
Maybe I can copy the tool design and weld something similar.

To clarify: the spring does not need to survive this operation. Is there a way to break the spring on purpose, relieving the tension?
I'm not gonna just put an angle grinder to it. Seems like a good way to lose fingers or worse. But maybe there is a way to break it in a controlled fashion?
Can the tension in the fibre glass spring be reduced with heat?

 

exactly
Now what state of disabled are you. Maybe a picture I have some work around in my head.

 

Since you probably have the Cradle on the ground, what if you wrapped/secured lower control arms with a chain go over the upper do the same other side. Then using a Truck binder tighten the chain to cage the spring, then remove the ball joint bolts and unwind the tension.
Or same design but with a floor jack sitting in the cradle pushing the chain

 

What is the current state of the assembly? Without the shocks or upper a-arms attached to the frame, the spring should already be fairly relaxed. I've never removed a front spring, but the pics I've seen show the lower a-arms to be about 70-80 degree down from the plane of the crossmember. If you can devise a method to get close to this angle, You can attack the spring with a grinder. (If you've never worked with carbon before, be advised it is nasty stuff to grind. Wear a Tyvec suit, a mask and gloves. Those little shards will be in your skin for days without protection.)

Just a thought to how I could do it because I hate grinding carbon. I'd figure out a way to lay the assembly under my F250 Diesel that weighs 7,400 lbs. Then release what ever is holding the spring tension and lift the truck up off it. I'd take the truck and the assembly to by buddy's shop that has a 2-post lift to put the truck on. Be creative.

 

This is what it looks like currently. I believe the limiting factor right now is the upper ball joints?

 

You could remove the shock and replace it with a thredded rod.
Weld or bolt a lower bracket to the thredded rod, and mount that to the lower shock mount.
Make the rod long enough to stick up a fail amount above the top nut.

This will secure the spring while you remove the inner upper A-arm bracket to allow the lower A-arm to move down freely. ( You could also remove one of the ball joints )

Now you can relax the spring by unwinding the top nut on the thredded rod.

 

I like this idea! I'll look into it. Other ideas are still very welcome!

 

That is a 1984 front suspension. If that spring is a code BMB "Z51" it is valuable to people looking for the heaviest rate front spring ever installed in a C4, and possibly worth salvaging.
I also notice that the lower ball joint wear indicator is well past the replacement-recommended point. The car that came out of had a lot of miles on it.

I like JoBy's idea. (One Swede to another. Cool.) Use the hardest, finest threaded rod you can find, and oil the threads. When I made a threaded rod deal like this for a high-load, I found some Grade 9 'long nuts' at McMaster Carr which is an industrial supply house in the states. The long nuts have more thread area. They aren't as likely to gall or pull the threads. Work safely. Think about the forces you're working with.

 

I've done this a couple of times. It's not hard. Get yourself a bolt and a coupler that will just fit between the upper and lower ball joints which oppose each other. Remove the cotter pin and nut on the lower ball joint. Unscrew the coupler to pop off the lower ball joint. With that out of the way, remove the spring supports near the middle and remove the spring.

 

Make sure you take these off first, before each side of the spring is unloaded...these will stop the spring from unloading completely. Also get the sway bar links and tie-rod ends unhooked prior to ball-joint unseating. IHBD is correct, that is an '84 front suspension, the curved sway bar is '84 only, he's also likely correct about the Z51, not only that the front spring is valuable, but the front sway bar is valuable to the right '84 base suspension owner....Big bonus, if it is a Z51, you should have the quick ratio rack and pinion. Quick check, measure the diameter of the front sway bar...25mm = Z51. This information is important, you'll likely want to source a straight sway bar from an '85-'87...also knowing you have '84 front spindles will be important if you ever want to upgrade the front brakes. Good luck with your project👍

Take these off right away.

 

Thanks for the advice! I have now removed the plates and sway bar and unhooked the tie rods. Still working on how to best go about compressing the spring. It looks more difficult than I first thought to get a threaded rod in place at the bottom shock mount. Also, I'm not quite sure what is limiting the spring right now. Could be the shocks, in which case I'll have to compress the spring some other way.

It's definitely a Z51 car. The sway bar diameter and shape mathces, and the steering rack is indeed the quicker one, which is a big win for me! 2 turns lock to lock. I was thinking about maybe upgrading that later in the project, but now I already have it. Sweet!
I assume the spring is also Z51 spec, I'll know for sure once I get it out. You mentioned sourcing another sway bar. Why is that? Is the one I have the stiffest you can fit in a 1984, but still softer than what was available for later cars?

You mentioned the Z51 leaf spring is valuable, what kind of prices are we talking about? I wouldn't mind some extra cash for the project, and I'm not gonna use it.

I'm a bit surprised about the model year. I bought it from a reputable junk yard here in Sweden specialized in older american cars (especially Camaros). The owner helped me import the parts from California early this year and told me the front was from a 1985. But I'm not really complaining about the mixup when I got the quick steering rack as a result.

 

https://www.corvetteactioncenter.com...uspension.html

The 1984 Z51 has the stiffest supension and nothing later comes close.

The 1984 Z51 front spring rate is 102 N/mm.
The 1984 base front spring rate, 63.5 N/mm, the same as an 1985 Z51.

Front spring rates went upp a lot in 1988 with the new suspension geometry, but wheel rates was probably about the same.
Base spring rates went up from 51.8 N/mm to 93.1 N/mm. 80% up ...
Z51 spring rates went up from 66.5 N/mm to 115.5 N/mm. 74% up ...
With an 74% factor, the 1984 Z51 would compare at 177 N/mm.

On the rear the 1988 update did not affect spring rates so those can be compared directly.

A base 1984 has 72 N/mm.
A Z51 1984 has 87.5 N/mm.
All following years, 1985-1996, the base spring rates are 39.9 N/mm and the Z51 spring rates are 57.2 N/mm.

Nothing comes close to a 1984 Z51.

The stiffer springs are actually easier to work on. They relax much quicker and are much straighter when relaxed.

You could put a strong beam across under the A-arms and use a ratchet strap to pull it up towards the cradle.

 

Look at the bottom of the spring on the driver side for the spring code. I can almost make it out by zooming the image way in. You're looking for BMB.

There is a date and a part number stamped into the crossmember on the front side, in the center. If the date is prior to August 1984, the crossmember was originally installed in a 1984 model year.

I think the suggestion to find a straight sway bar was for packaging and appearance in the new installation. Both std and Z51 1984 sway bars have the bends. The bend was for clearance with the fan shroud that was used in 1984 only.

We're (at least I am,) curious: What vehicle is this suspension going into?

 

I've had a 1984 Z51 front spring in the classifieds, there was zero interest.

 

I guess I'll put it up for sale in a Swedish Corvette FB group or something a d see if there's any interest. The spring fits all 1984-1987 cars, correct?

This C4 front and rear suspension is going into an 1975 Opel Kadett Coupe. Originally, that car had a 1.2 liter engine with ~60hp and 155/80-13 wheels. Everything in the stock suspensions is dimensioned for that. Swedish rules for modified cars allow it to have just over 300hp, if the chassis components and brakes support it. I could try to upgrade and reinforce the stock stuff, but I decided to get a complete package from another car instead. This way I get better geometry, steering servo, an LSD, adequate brakes etc.

The body has seen better days, but it's not that bad for a 70s Opel.

 

Update: I am lucky in multiple ways this suspension is from a Z51 car. I tried loosening both the top nut on the shocks and also the bolts that hold the "shock mounting plate" to the lower wishbone to the end of their threads. Thanks to the Z51 spring being lower profile in its relaxed state, this was just enough to get it to a point where there was no pressure at all on the top shock mounts anymore. I removed the shocks, and now I can feel a slight wiggle in the suspension if I shake the hub by hand. So the suspension does not seem to be loaded at all anymore (and the force must have been very small before). I'll try disconnecting one of the lower ball joints tomorrow and see if I can pull the spring out.

 

Success!

I took the advice from 383vett and pushed the ball joint out with a long bolt and nut:




After doing the same on the other side and removing the spring brackets in the cradle, the spring came out very easily.




To summarize, this is what worked for me, with a Z51 spring:
1. Remove the shocks. There is a little bit of tension on them, but nothing to worry about. (Caution, this tension might be much higher with a base model spring)
2. Remove the plates circled in red by '78CorvetteS.A. above.
3. Pop the lower ball joint using a bolt and nut like pictured.
4. Remove the shock mounting plates from the lower wishbone.
5. Remove the spring mounting brackets from the cradle.
6. Pull the spring out. Done!

 

Something to check: