rear suspension help

[z400rider8787]

i have a 70 GMC long bed and im doing a high performance street build with it. im going with a 383 around 500 hp and a 150 shot. im gonna drive it on the street and i want to get a good rear suspension set up to make it hook up. its a leaf spring truck now. should i switch to trailing arms or go with something custom like 4-link? i dont wanna break the bank but im gonna need the traction so whats my best (and cheapest) idea? thanks guys

[Super73]

Well, the cheapest and easiest thing might be just adding Caltrac bars to it. But then the rear spring may be too stiff for it.

The truck arm suspension works very well and would consider that the next solution. But if you are lowering it, your going to need an adjustable panhard bar. You also need to decice if you want the longer panhard bar fromthe older rear ends or the shorter one from the later ones. The longer one will help keep the rear more in th center under a bump on the street. If you decide to swap to this, you mine as well make some adjustable rear control arm brackets: http://67-72chevytrucks.com/vboard/s...d.php?t=278864

Also, while there is a lot the rear does, the front can aid just as much. I haven't completed this thread, but it might be worth the read: http://67-72chevytrucks.com/vboard/s...d.php?t=326863

[z400rider8787]

i really like your trailing arm brackets, and they look fairly easy to make. i have a friend who is a metal genious that could help me build those in a day. i have a pair of 5 inch drop coil springs i could use. all i need to do a swap would be the rear end brackets, panhard bar, and the control arm brackets like you made. and this might be a stupid question but what exactly is are caltrac bars? also would i need a different type of spring or would the drop coils i have work? in the front im running tubular lower control arms and a disc brake spindle set up off a 71. 3 1/2" drop. maybe i could just pick up some control arms off e-bay and clean them up and build some brackets for the cross member like you did, weld on the rear end brackets and spring cups. and i should be good right? that sounds pretty cheap, what do you think?

[Super73]

A lowering spring is typically not what you want. They are a short spring with a heavy spring rate. You want a longer spring with a lighter spring rate. I have heard of guys using Jeep Wrangler and Jeep Cherokee springs.

Caltrac bars are used with leaf springs.

Once it's all togetherm you may have to play with springs and shocks to et it to work right..

[z400rider8787]

I think ill just put it all together with the lowering springs so i can drive it and see how it works, then play with springs. have you ever heard of anyone using a coil over with trailing arms? is this even possible? and how would the jeep springs work on the street? i cant get too far to the race side and lose all hope of street driving, i dont want a trailer queen.

PS: i hope you dont mind but i think im gonna copy your trailing arm bracket design.

[z400rider8787]

i think the caltrac bars idea wont really work with my application. my main reason for getting rid of the leaf springs is to run a wider tire, because im gonna need it. my motor is gonna be 500-550hp with a 150-200 shot. thanks for all your help, this is why i love forums

[Super73]

No problem copying my LCA design, that's what it's there for.

There are guys on this board running jeep springs as lowering springs. They are long and soft. Make for a non-stiff ride and give you the drag racing performance you will need.

DJ is running a coil over behind the axle with the factory trailing arms as are a couple other guys. Your just going to need to figure out what to do about the panhard bar.

[Wild83C10]

You can run the caltrac bars with the calvert split mono leaf spring. You will be able to fit a big enough tire on there to get enough traction to break plenty of stuff. There are plenty of trucks on here running stock leaf spring suspensions with a big block and more power.
Like super73 said you should concentrate more on the front then the rear and work on weight transfer. You want taller spring that you can compress to store plenty of energy for a hard launch. Buy some adjustable shocks so you can loosen the front up. You don't want the rear to squat that just unloads the tires. You would also play hell on your driveline angles.
I have been going back and forth on the trailing arm setup, I have everything I need except the coilovers. Still haven't decided if its worth all the work. It's not expensive to make the conversion just time consuming and a lot of measuring.

[z400rider8787]

so the front is basically the same idea huh? a long soft spring? i want to maintain about a 3-5 drop to keep the street looks. what springs should i look for? just a stock jeep spring? im assuming they are the ones from the front.

[z400rider8787]

i think the measurments i took from inside of the wheel well to the outside of the leaf spring would allow me to run about a 10 in tire without risk of rubbing. you really think thats gonna be enough? and i think i would much prefer the coils anyways just to soften the ride.

[z400rider8787]

PS: does anyone have some pics of the stock panhard bar location? so i can get an idea of how hard it will be to graft one onto my truck

[Super73]

Jeep springs are going to be way too light of a spring rate to keep the front from sitting on the bump stop. I know this as I tried. Does you truck run right now? Can you get it on a scale and give me some weights? Also, I would need you to take one measurement in the front suspension and I could give you a real good idea of what you would need for a front spring. Need you to do some homework on your end to give you a good answer.

[Wild83C10]

You can still get a nicer/softer ride with leaf springs. Just remove the overload leaf and shift some weight to the rear, which you should be doing anyway.
What kind of tire? How much side wall?

[z400rider8787]

well right now the truck is in day one (you'll get if your an overhaulin' fan) completely disassembled. so i cant get you measurments now. but what i can tell you is the front spring im gonna be using when its first put together is a 3.5" drop spring which seems to be just about as stiff as the stock ones only shorter. i cant tell you if this is an aftermarket spring or a cut stock one... i got them for free with the disc setup from a friend. i know this isnt gonna be great but it will let me drive it. Im thinking about rear springs right now, ill worry about the fronts when im trying to lower ET's when its finally worthy of the track. so would a jeep spring work for the rear? ill be moving the fuel cell/battery and whatever else i can back there so its gonna add more weight over stock. i still wanna retain about a 3-5 drop so i can keep the street looks. thanks for all your help guys i know im asking a ton of questions but i just like to pick peoples brains that know more than I do

[Wild83C10]

If you are using stock springs that are cut that much then it will ride like crap. You can definitely tell if they are aftermarket coils. They will have a larger diameter wire and will be a lot stiffer.
Make sure you buy the proper shocks.

[Super73]

If you go to a rear trailing arm set up, I have heard rear springs off the Jeeps Wranglers work. Here is a link to someone that has run them. Claim a 4" drop.

http://67-72chevytrucks.com/vboard/s...ht=jeep+spring



This is an FYI.. When I went from the lowering springs I bought and installed to the "drag" spring I have in it now, there was a world of difference as far as ride quality. The lowering spring rode very stiff compared to the Cadillac spring that is in there now.

[z400rider8787]

ya i compared them to my stock ones, they are definatly aftermarket. alright ill look into the jeep springs

[z400rider8787]

alright i looked into it and i decided the cheapest and best way for me to go is coil spring swap. im gonna look for some trailing arms on ebay or there is a guy in this area that all he does is part these trucks out so im sure i can get a set there.. im thinking 250 max for some old stock trailing arms. then ill pick up some wrangler springs off of ebay or at the upcoming 4x4 swap meet. then build some TA brackets for the crossmember then get a panhard bar, weld a bracket on the rear for it. then get the TA mounts for the rear and weld them on. then i think thats it can you guys think of anything else?

[Super73]

IMO, you shouldn't be paying more than $250 for:

Cross member that the trailing arms bolt too
Trailing arms
Factory Springs
Pan hard bar

Through your local pick and pull, you can get the rear springs for under $50




I'm assuming your rear is stockwith nothing done to it right? 5 lug? Might be worth buying the rear suspension and the rear to go with it and then sell your current rear. Reason being, the panhard bar and trailing arm mounts will already be in place. It should save you time and money in the long run.

[Wild83C10]

Don't bother buying trailing arms, make some. Do a search for adjustable trailing arms. Someone on here built them and provides all the details. It was in the suspension forum.

[z400rider8787]

alright guys thanks for the help im on the lookout for a 3.73 coil rear. hopefully i could find one with a posi in it but ill probably have to get just one that has the gears and put a locker in. as for buying/ making some ill look into that too. my crossmember is the same and already has the holes in it for the mounts

[SCOTI]

I've been browsing through a lot of these threads updating my 'education'.
Have you guys given any thought to airbags in the rear as a shorter, softer spring w/easy adjustability?

[Super73]

Airbags don't store energy like springs do. If your vehicle is set up to squat, they might work out ok, but for antisquat and planting the rear tires, well, I don't think they would work the same. But that is opinion and not researched fact from my end.

[SCOTI]

Basic physics would suggest an airbag acts very much like a spring when compressed to a certain extent: the bag (spring) will want to return to its uncompressed state or size (squish a ballon & it distorts, unsquish it & returns to its original form immediately). I'm not educated enough to calculate how much difference there might be between the two different forms though.

ART is working w/drag applications now & there was even a video posted by Tony in the suspension section regarding improvements made after switching to Shockwaves vs. a coil-over.

Might be worth checking into.....

[djracer]

I might need to tell them I'll test some shockwaves with my new motor.