I was looking into putting Chevy's in the rear when I do my SAS and putting the rears in the front to save me some cash. Now everytime I read a post on 63's it says move the shackle mount back and the spring mount forward. I can move the mount forward no problem. But in about a week my frame will be bobbed at the rear shackle mount. That leaves me to wonder how do I make up for that 4in I cant move my shackle back? I keep hearing double shackle if you want to not move the shackle mount, then reading not to do that its half assed ect. So whats so bad about a double shackle and more importantly how is it setup exactly? I've searched and cant find an explanation on it.

 

the chevies are a longer spring, so, if you want to keep stock wheelbase, youd need to move both mounts. If you bob, when you go to the chevies, grind off the old perches, get new ones, move the axle forward, and put the new perches on, so you keep a good pinion angle with the shortened wheelbase. Send out your rear shaft for modification (only a couple hundred bucks). Be pretty sweet.

Not sure on the double shackle thing.

 

Ok I found a picture of the double shackle setup



Now it seems like inorder to have a properly functioning double shackle setup you need to have the frame there for the top shackle to lay against when its horizontal. I can't figure out what the solution should be for a bob'd frame...

 

So if I dont move my shackles it will slide my rear forward correct? I like my wheelbase where its at, not too long not to short. Good thing I found this before I bob my frame...

 

essentially yes. It is simply a longer spring, so it will move your rear axle front wards. Don't be too quick to throw it out, however, since you can easily move the front axle as well during a SAS. Many folks move the axle up about 3" in the front, to give better approach angle. Since you are hanging the axle from scratch, its not a big deal. Do some research on the chevies, find out how much farther forward they move things, and then see if you can compensate with the front. An inch or two difference between wheelbases isn't going to be that noticeable.

That double shackle looks a bit sketch. Be fine probably offroad, but i'd be leary of something like that on a truck that might see 60-70+ on the highway.

 

Don't run the double shackles.

A friend of mine runs them on his 81 with Chevy's and hate how it unloads so much.
I value his advise more then some random person on the net.

 

Beleive me i think it looks sketchy too. Especially since my truck does see 75mph. I'm gonna draw up some ideas to make custom shackle mounts off the end of the frame where I cap it. I'm just thinking that say I can get the mounts 3" back will a longer shackle add a little compensation or will it always lift before it frees up space?



Heres my idea:




The only problem I see with this is that the shackle will be the first point of impact was I to back my truck up straight into a wall. What do you guys think?

 

moving the rear axle forward means moving the gas tank too.

the easy answer for a frame bob and chevies: don't. use some different springs or better yet, link the rear.

otherwise you are on the right track with your above diagram

 

Well since the frame isnt bobbed yet looks like I might be leaving the frame 3" longer than I was going to...

 

How much are you taking out? I'm 13" bob rear with a 4" out of the frame. Mount the shackle mount on the bumper.

 

It seems like your drawing would work... assuming it is properly supported.

That said, if you are going to go through all that trouble, why not just limit your frame cut to allow you to mount the new hanger still on the frame? Probably stronger than adding a piece like in your pic anyway.

The shackle is still going to hang out there, but would be no worse then on a Jeep or similar with shackles at the front of the front springs. I've seen that setup put shackles to the rocks a good deal off the time and still survived.

Just build a rear bumper accordingly for protection and be aware of the possible shackle vulnerability.

 

Thats what I decided to do no point.