63" Springs vs. Shackle Flip ?s

[jepj2000]

I'm trying to get everything in order for when I do my 1-ton axle swap on my '77 J10. My goal is to have it sit about the same hight as it does now which is stock springs and a SOA in the front and blocks in the back (all done by the PO). I obviously want to get rid of the blocks and add the needed flex to the rear suspension without going over about 7" of lift.

My first questiong is how low of a ride hight can I get with moving 63" springs to under the frame? I would set them up so the wheelbase is not changed, and I have a short bed.

Second what is the difference in the amount of flex between 63"springs under the frame and a shackle flip setup? I've seen the pics of the shackle flip on TT's fabworks website and they look pretty flexable, but have not seen some good flex pics with 63" springs.

Any additional information on either setup would be a great help. Pics of the different setups also would be great.

Thanks,
Rankin

[Slick Willie]

My first questiong is how low of a ride hight can I get with moving 63" springs to under the frame?

It depends on a lot of things: your shackle angle, where you mount the spring hangers, difference in stock springs vs. 63's, etc. For the rear springs, I mounted my front spring hangers just in front of the /--\ arch in the frame, so they're sitting about as low on the frame as they can go (most lift). This will make the rear sit as tall as possible compared to mounting the spring hangers inside the /--\ arch. The rear hangers on the rear springs are also outside the arch, so my mounted hangers are as low on the frame as possible. I had to do this due to the length of the 63" springs and the longest possible wheelbase without tying the hangers into my rear bumper. But my spring eyes are as high as I could get them in the hangers so the springs would be as close to the frame as possible (least lift). I goofed at the beginning due to a rush to complete and my shackle angle at ride height was flat as possible, pointed in the rear direction. So I had no stuff flex from the shackle, just droop. My springs negatively arched instead of the shackle giving. So I remounted the shackle further back, and at ride height, the shackle is at an angle, where it should be. Now I get a higher ride height, but less negative arch in the spring when it's stuffed. Lesson #1, take a lot of measurements before you mount spring hangers. And measure with the axle attached to the springs. :banghead: Either way, my ride height for the rear had about a 3" difference just from adjusting the shackle.

Shackle flat:
http://longhornoffroad.com/garage/gallery212/d/3182-2/In+the+street+III.JPG

Shackle correct:
http://longhornoffroad.com/garage/gallery212/d/3469-2/No+Doors.jpg




Second what is the difference in the amount of flex between 63"springs under the frame and a shackle flip setup?

Longer springs will flex better than shorter springs...that's physics for ya, but most people know that. One thing to think about is the length of the shackles in use. Stock FSJ shackles are shorter than the shackles that bolt to Chevy 63's. So depending on what shackle you use, the longer one will allow more flex/stuff with the same spring. I think your's has 57" springs (4 or 5 leaf?). So the extra 6" will allow more travel, but more than that, the Chevy 63's are 3 leaf with an overload, and stock springs are (correct me here) 4 or 5 leaf with overload. The Chevy springs are thicker. My stock GW springs should be the same as your J10 springs, and they didnt' flex all that great. But they had overload springs on the bottom, IIRC. I took the overload off the Chevy springs and they flex wildly. Something else to consider is the thickness of each spring pack. The overload spring is thick as heck on the Chevy springs, and not as thick on the FSJ springs.

So for me, running 57" stock 4 or 5 spring pack with an overload spring on bottom, compared to a 3 leaf pack of 63" springs with no overload spring on bottom, the flex is night and day. I think if you took off the overload on the 57" springs, put chevy shackles (longer) on them, and shackle flip kit, there would be a much less difference in Chevy 63's and shackle flip. I don't know how much, but I bet there wouldn't be much difference. Not enough to tell without a tape measure.

Sorry this was so long. Hope it helped a little. :thumbsup:

[chad grande]

I am running 64" Alcan springs in the rear of my J-4000 and as stated shackle angle and length are criticle. I solved this dilema by mounting the springs under the frame and putting the shackle mount above the frame with a 10" shackle, like on a desert race truck. With the spring in the flat position the shackle should be at 30 degrees, this will allow the spring to invert easily and gain lots of upward flex. Alcan suggested that I not invert the spring more than 4" to maintain a decent spring life.

[Tad]

http://members.cox.net/pmountsoa/testrun1/03riverbed.JPG
It's very decent flex (63's with overload removed).
I could probably get another 4-5" by relocating my shock mounts (again), I just have not had much time to tinker this summer.

[Noticon]

Ok for those that have done the inboard springs on the rear how much off camber stability is lost? Does it matter if you run 63" Chevy springs or not? I will also post this on my Noticon build up thread as well. Thanks all!

[shepherdskeep]

Here is my setup on an RTI ramp - stock springs, stock shackles, Tad's flip kit installed, flares cut off, tires at 25psi. Hard to tell because of the shoddy weed-eating job, but my rear tire is on the edge of the ramp.

http://i81.photobucket.com/albums/j226/shepherdskeep/Chief/RTI%20ramp%207-4-07/HPIM1042.jpg
http://i81.photobucket.com/albums/j226/shepherdskeep/Chief/RTI%20ramp%207-4-07/HPIM1043.jpg

With an RTI of barely under 1000, I'm satisfied with my stock springs. :thumbsup:
Off camber, it feels more stable than expected.
Future plans include 2" longer shackles, both for a bit of lift and a little more droop.