CJ to Wrangler height conversion?

[Kane]

A stock wrangler has a flat spring, duh we all know that.
A stock CJ has some curve to it. duh again.

So what does a lift of 2.5 inches equal for a CJ if you were to use a wrangler lift spring? Because that arch would be different for each lift due to the difference in stock arch. Would a 4 inch wrangler spring equal a 2.5-3 inch CJ lift. Inquiring minds want to know.

 

[tdkask]

I'd like to know this too. If a 4" CJ kit clears my 33's fine, would a 4" YJ kit have the same clearance? Or is a 4" YJ like a 2.5" CJ?

 

[LASTCJ786]

I know you can run YJ rear springs on a CJ. I think a 4" lift is a 4" lift
from stock on any Jeep.

 

[TDHofstetter]

It's gonna' be close - I know. I happen to be in exactly that position right now - a couple days ago I dragged home a set of Wrangler springs for one of my CJs. Didn't notice then that they're lift springs, but it's sure obvious now. I WANTED flat springs... oh, well.

They're lifted about 4", and it takes a lot of weight to flatten 'em at all. They'll wind up being a good solid 4" lift, I'm sure, when I've done the conversion (which I may not DO now, unless I can get hold of a set of real STOCK springs).

 

[73CJ]

2.5" Cj is close to 2.5" YJ but all depends on the spring rate of the pack. Do some Goggling on spring manufactures. They give the spring rate, lengths etc.
My Trail Master 4" had a spring rate of 500#/in. Rode like a tank and cracked the frame by the spring perches. Do not recommend TM. Besides they wouldn't honor their lifetime warranty on shocks.

I've got YJ 2.5" OME now with a rate of 230#/in or so. They are great.

 

[81laredo]

would a set of Warngler Springs on the rear of my '81 CJ7 produce a smoother ride?

 

[TDHofstetter]

It might, but it might also produce a rougher ride. It depends upon the spring rate.

CJs and Wranglers were all produced with three different spring rates each - soft, standard, and heavy-duty. If your CJ currently has soft springs and you switch to YJ heavy springs, your ride will turn into something similar to that of a farm tractor. If your CJ has standard springs and you switch to YJ standard springs, you may not be able to discern the difference; they compress about as much per inch of travel. If you switch to SOFTER YJ springs, or softer CJ springs, your ride will soften.

 

[Old Dog]

would a set of Warngler Springs on the rear of my '81 CJ7 produce a smoother ride?

It might, but it might also produce a rougher ride. It depends upon the spring rate.

CJs and Wranglers were all produced with three different spring rates each - soft, standard, and heavy-duty. If your CJ currently has soft springs and you switch to YJ heavy springs, your ride will turn into something similar to that of a farm tractor. If your CJ has standard springs and you switch to YJ standard springs, you may not be able to discern the difference; they compress about as much per inch of travel. If you switch to SOFTER YJ springs, or softer CJ springs, your ride will soften.

81 here's a link that might help you understand what Tim ia talking about
1976 - 1986 Jeep CJ Leaf Springs
Look at the spring rates for both the cj and the yj to see how they differ.

 

[81laredo]

that answers my question.
I have the OEM 6 leafs in the front and 6 leafs in the rear, this looks to be heavy duty springs fore and aft. I did notice the CJ get a bit stiffer with the new polyurethane spring and shackle bushings and shocks (not heavy duty) but some of that was expected since the old parts may have been original. The CJ rides much better with a couple hundred pounds in it (wife and dogs).
I wouldn't mind if the CJ was a bit lower so looks like just shifting to 4 or 5 leaf springs would help, by the way it does ride similar to my Ford 8N Tractor right now.
Could I simply remove one of the spring to get a softer ride or could this create more trouble? If so which one would be the correct one to pull out of the spring pack.

 

[Kane]

81Laredo I have done this before with good results. it is just like when someone puts an add-a-leaf lift and the ride gets stiffer. Generally people will pull out the second or third longest leaf. I saw about a 3/4 inch drop on mine when i had Pro-comp springs. they are stiff springs and this helped allot for ride quality.

 

[73CJ]

Nice link Old Dog, but spring capacity (lbf) and spring rates (lbf/in) are not the same.

example: capacity = lbf = (lbf/in) x in

= 630lbf = (210lbf/in)x3in = Soft 3inches travel

=630lbf = (315lbf/in)x2= Hard 2 inches travel

It's the spring rate that is important here to determine the ride.

 

[81laredo]

I would like a smoother ride so that the CJ can be used as a commuter when needed. The CJ7 has the 6 Leaf Spring Pack and it looks like these are the Heavy Duty ones so I am considering removing the second one down, here are a couple of pics, any ideas?
I would also like to rebuild the Spring Pack while I am at it. Are the Plastic inserts and retainers available anywhere

 

[LongHorn]

I would like a smoother ride so that the CJ can be used as a commuter when needed. The CJ7 has the 6 Leaf Spring Pack and it looks like these are the Heavy Duty ones so I am considering removing the second one down, here are a couple of pics, any ideas?
I would also like to rebuild the Spring Pack while I am at it. Are the Plastic inserts and retainers available anywhere

The factory put more leaves in the rear packs to carry the weight of the hardtop & to limit spring wrap.

 

[TDHofstetter]

It looks to me like that leaf was ADDED at some point, probably to improve the Jeep's height (sagging springs). Removing it will lower the rear significantly, besides softening the ride.

Spring rate and weight capacity kinda' work together here, since - if you buy complete spring packs - choices are Limited to a few standard packs.

I've never seen either the retainers or the plastic snubbers for sale anywhere. You could probably make up retainers from plumber's tape pretty handily, but making the plastic snubbers might be a little more of a challenge. Surely somewhere there exists some sort of black (UV-resistant) plastic SOMETHING about that same shape & size... but I can't think what nor where.

 

[Old Dog]

Nice link Old Dog, but spring capacity (lbf) and spring rates (lbf/in) are not the same.

example: capacity = lbf = (lbf/in) x in

= 630lbf = (210lbf/in)x3in = Soft 3inches travel

=630lbf = (315lbf/in)x2= Hard 2 inches travel

It's the spring rate that is important here to determine the ride.

73cj, I know that spring cap. and rates are not the same, but thats how most co. list them.
Could you explain your formula's to me better I don't understand. but would like to. I'm not sue why you are taking one times 3 and the other by2.

 

[TDHofstetter]

I think he's taken a hypothetical live load of 630 pounds and demonstrated that load applied to two arbitrarily-chosen spring rates, those being selected to make for easy math - the stiff spring rate being the 315 and the soft spring rate being the 210 - just to demonstrate that while both springs will support a 630-pound dead load, the soft spring would deflect 3" where the stiff spring would deflect only 2" under the same load.

Does anyone actually have any information about real spring rates for CJs? All I can find is load capacity @ stock vehicle height, no information about the arch height of the unloaded springs (from which we could calculate spring rate).

 

[81laredo]

No the Springs are OEM, I got two from a local wrecking yard but only used only one. When I got the CJ the Rear Spring Pack on the Driver's Side was Sagging and replacing that one made the CJ level out. The Front Springs also have that full length Leaf at the Second position.
I'm OK with the CJ being lower, I just don't want to produce an unsafe ride. I would like to find a compromise between having the Hardtop or the Soft-top on. With the Soft-top and just me it rides like a Buckboard. I am interested in the Wrangler Springs on the Front because longer makes sense to help with the ride.

 

[TDHofstetter]

I've been looking pretty hard at that YJ spring conversion... and I'm going to back out of it for mine. I've got one set of YJ springs in hand right now and a guy trying to sell me another set, and... well... the rear springs don't buy you anything except more project, to begin with. They're almost exactly the same length, even for a '74 CJ5 . In your case, for an '81 CJ7 , they're ALL almost exactly the same length (within about an inch). In my case, for the early-AMC CJ5 , the YJ fronts weren't greatly longer than the CJ's, just enough to make the front shackle mounts a little hairy, while I move the pivot mounts rearwards to keep the axle centered so I don't grind up my fenders on a nosedive (and so my wheel positions wouldn't look all out of whack).

Then both sets of YJ springs, the one in hand and the one the guy's trying to sell me, were of significantly lower capacity than the springs already under the CJ. Hundreds of pounds lower, in fact. Sure, it'd make for a softer ride... but there goes my quarter-ton load-carrying capacity & ability to pull any sort of trailer with any measurable tongue weight.

It'd be silly to convert just one end, too, without converting the other end... so last night I just broke down & ordered new shackle mounts & shackles & cetera. I'm putting it back stock.

 

[81laredo]

I didn't even think about my Hardtop. I would like to keep the CJ as stock as possible but an upgrade in the ride is very attractive.

 

[73CJ]

Here is the data from the factory manual with the spring rates. The spring rate is how many pounds of force does it take to compress the spring 1". There is a lot to the spring metallurgy. Some springs can bend flat or more, some will break if they are loaded to flat.

Rancho catalog lists the YJ 1-1/2" and 2-1/2" lifts at 174 lbf/in front and 200 lbf/in rear.

The OME YJ springs I used were 148Lbf/in.

The specs are usually in the catalogs, but you may have to dig.