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Unread 06-16-2003, 03:23 PM   #1
merr6267
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Shackle Reversal, and driveshaft mods.

Hi everybody, I'm Phill.
I've been reading for a while and I finally decided to post. I have a 1980 CJ-7 and I recently blew up the stock 304. I now have it in a million pieces, and I am debating about a shackle reversal system. I am looking at the MORE system, but I was wondering how much travel the driveshaft actually needs. I know that it nees to be modified to accomodate the extra travel. The problem is that my shafts were already modified a few years ago. Do any of you have any idea how much travel that I will need in my shaft. I currently have about 4".

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Unread 06-16-2003, 04:07 PM   #2
rustyCJ
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maybe i am completely wrong in my thinking on this but i dont think you gain any extra "travel/flex" from a reversal. you dont really change the geometery of the suspension that much. you still have a spring with a pivot and a shackle that allows it to flex.

isnt the reason the driveshaft needs modded because the shaft actually collapses during spring compression now instead of extending like before.

it was my understanding that if you did a shackle reversal you could get away with just cutting your shaft down so when sitting on flat ground the shaft was almost all the way extended so when the spring compresses and the axle moves rearward the driveshaft can collapse.

i havent really looked into the reversal thing that much and never wheeled with a jeep that someone had done it to so dont pay too much attention to me.
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Unread 06-16-2003, 10:58 PM   #3
magicmudder
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I posted on this a couple of days ago. I just finished my shackle reversal about a week ago, but I was changing gears, so I had to wait to put the axle back on. When I did put it on, my (unmodified) driveshaft was about 1/2" too short if you jack up the jeep from under the axle and allow the springs to droop. But this is just about as far forward as the axle will move.

You should be good as far as length is concerned, but like RustyCJ said, the thing you have to worry about is whether or not your driveshaft will collapse enough when you flex your suspension. With a lengthened driveshaft, this doesn't change. I tried jacking the jeep up numerous ways to simulate flexing on the trails, but I decided just to get everything back together and roll it outside and use a forklift to flex the jeep real good and see if just a lengthened driveshaft would work. I wasn't expecting alot of things that happened when I did the shackle reversal even though I'd researched it alot. Check my earlier post a couple of days ago and see the problems I was having.

My tierod and draglink were really close to hitting with the dropped pitman arm, but CSP suggested MORE had a kit to fix all the problems associated with the reversal. Hopefully tomorrow I can test the driveshaft and see if it will travel enough without bottoming out when the axle moves rearward and let you know.
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Unread 06-16-2003, 11:25 PM   #4
merr6267
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I realize that the problem lies in the need for the driveshaft to be able to collapse more than a stock shaft. I was just wondering if any of you had actually quantified those numbers. Does it need 4 inches of travel (extension-collapsibility), 6, 8? Does anyone know how much?

Thanks for your replies, and I look forward to reading further.

Phill
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Unread 06-17-2003, 10:32 AM   #5
rustyCJ
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did your stock driveshaft limit articulation? if it didnt then your jeep doesnt flex enough to warrant a long travel driveshaft even if you install a shackle reversal. it made need lengthend/shortened depending on where your front axle ends up being after the reversal but(i may be mistaken)you gain no articulation benefits from doing a shackle reversal so the stock slip joint is adaquate.

magic, you said that was with the axle moved as far forward as it would go? so you could have moved it back an inch or so and used your old drivehsaft? does the MORE kit allow that much tweaking of the front axle location to let you do that?
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Unread 06-17-2003, 10:14 PM   #6
magicmudder
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Sorry Rusty, I wasn't too clear. I don't have the MORE kit, I used a rough country. I made it sound like you could adjust the axle forward if you wanted, but it just stays in one position on the springs as normal. See if this makes more sense.

With the tires on and the jeep sitting level, the driveshaft is long enough, but if I jack the jeep up from the frame and let the springs droop, the driveshaft is about 1/2" too short as the axle is at the most forward position it will go (ie. shackles in rear have swung forward moving the axle forward). I've used jacks and my forklift to simulate different flex positions, but the axle really doesn't move any more forward than when the jeep is just jacked up from the frame.

I have to have a new driveshaft made and was just trying to make sure I'd tried different flex positions. If I needed a longer slip yoke, I was going to call a 4x4 shop, but if it just needs lengthened, I was going to get a buddy of mine who makes them for race cars do it. After using the forklift tonight, I'm pretty sure I don't need a longer slip yoke. I'm going to try flexing it one more time when it's light outside and not raining to make sure.

merr, what did you have done to your driveshaft before? Was it just lengthened. I'll measure the actual travel of the driveshaft tomorrow and maybe that can help you out a little.
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