Rear Suspension Sag and Open Different Rear End.

[74Runneer]

I have a 1974 Roadrunner with a 318 in it and I'm going to start working on the suspension. The first thing I want to deal with is the saggy rear end. Is it better to add a spring, re-arch the springs (where would I do this?), or should I buy new ones? Id like to raise it up about an inch or 2 and I'd prefer to spend as little money as possible but I also want to do it right. How does adding a spring effect performance? I think that is the route I'm going to go.

Second thing:
I took my car to the drag strips and learned that I need either an lsd or a posi because the one tire fire was embarrassing, and I couldn't launch very well. I figured that while I'm figuring out my leaf springs it would be a good time to swap rear ends. What's the best way to find a decent 8 3/4 with 3.23-3.55 gears with either a lsd or posi?

Thanks everyone.

 

[747mopar]

There's a few limited slip rears in the for sale forum regularly but expect to pay about $400 or more for one. I'd consider buying new springs simply because they are so cheap anymore that, check Summit racing but I've had sorings re-arched with good luck as well. Check your yellow pages for spring shops or just ask around the truck garages.... they're usually not to expensive to have done.

 

[Bruzilla]

Good luck finding someone to rearch springs. All of the shops in our area have stopped doing them for cars and only work on truck springs these days.

I have a 74 Roadrunner and put the Mopar Performance Super Stock springs on it. The springs are cheap, but you'll also need to buy a pair of hangers. So the price will be about the same as for a cheap set of springs.

You need to be careful when ordering your parts because the 73 and 74 suspensions are different. The 74 cars use on oval-shaped end on the forward part of the spring, which moves the length of the front section of the spring .75". The length for a 73 is 22", and the length for 74s is 21.25", so when you get springs make sure you're getting the right length. Also, the 74 cars had a rubber-isolated rear suspension, so you need mounts for the rear end that have a large hole (about 1.25") and not the smaller 1/2" hole.

Also, if you get the MP SS springs, and buy the MP hangers, buy the ones for the 68-69 B Bodies. The ones for the 71-74 B Bodies don't work.

 

[74Runneer]

What about the add a spring kits? Do you guys have any experience with those? I wonder if they mess up the spring rate?

Also, are leaf springs for big blocks and small blocks different?

 

[Dieselholic]

I would suggest ordering new springs from ESPO Springs N Things. I ordered mine from there along with new mounting bolts, shackles, front hangers, and U bolts. They also press in the new front bushings. They need to know year of car, motor size, front bushing shape, and whether or not you are keeping the rubber isolators. I would definitely recommend them. It took all of the guess work out of it for me.

 

[idrivemopar]

I 2nd ESPO Springs and things, got my 73 RR springs from them. Also, if you are redoing or replacing the rear end, maybe you can find one cheap with a bad diff and put in a Eaton True track diff, I love mine, that is if you want to spend the bucks for one.

 

[UKPlymouth]

If you want a quick cheap fix just add a leaf. Really cheap and restored both ride height and handling to my RR. Living in the UK I can't afford to ship springs but if I did ESPO look good.
As for gears, when I do mine I will go from 3.23 to 3.73
I have a built 340 and it now needs more gear.