Shackle Reversal

What is gained by reversing the leaf spring shackles on the front of a 75 CJ5? What is lost?

 

Git them shackles outta there so they don't jab into rocks-n-logs....plan on long travel driveshaft stuff too. That axle's gettin forced forward when teh tires come to obstackles-aint no good.

 

Better handling with the shackle reversal, but x2 on the long travel driveshaft. I have seen several folks running the reversal and having to replace t-cases and transmissions because of the driveshaft being forced back into the t-case.

 

I'm lucky, my '56 was built that way!

 

Any way to know if the driveshaft has already been set-up for long travel?
What do I need to do the set-up?
Does the "fix" prevent the driveshaft from traveling too much or allow it to travel more than stock?

 

I don't know if you'll gain any better ride from a 75 anyways. I have one and bought new springs, 4in. lift, but the ride is rough as a cob even with new springs. Just old tech. I guess. I've always have been told the best thing one can do is convert it to YJ springs for comfort

 

I just converted to a custom YJ front spring and did a shackle reversal on my 72. It is like driving a different Jeep. I also moves all the stress and twisting of the shackles farther back on the frame where it tends to be a little stronger.

 

If you think about hitting a bump or rock or anything, you hit it with the front of your tire. The natural reaction of the tire is to be pushed back just as you would if you bumped in to something rigid. With the shackles in front as the spring compresses they rotate or move in an arc foward. That is opposite of the direction the tire wants to move when it hits something. With the shackle in the rear it lets the tire and suspension move in the direction it needs to absorb the impact. Also with the shackle in the rear you are pulling the spring when you drive instead of pushing it. That usually makes it want to follow what is pulling it instead of having something push it. Of course this this all gets tossed out if you spend a lot of time driving backwards!

 

I think it is an over-rated modification.

 

CJ John, did you just do the yj spring on the front only and did you go spring over or stay under, Also was the yj spring something custom or just a stock spring?

 

I would tend to agree, although all the race cars at the Jeep dealer had it. In that case I expect it's meant to keep from bending the spring if you hit an obstacle at speed. It's hard to believe that Jeep would have built all those CJs with shackles forward if they didn't drive better that way.

The semi-race '72 Renegade that they built while I was hanging out there (meant for reporters to run a Baja race in) did not have reversed shackles, but had blocks welded on the frame to keep the shackles from overextending.

<edit> IIRC Moby Dick (the white POR rally Wagoneer) had forward shackles. All the Jeepsters (Baja/Mint cars) were reversed.

 

I believe that if the spring is flat when static, it will get shorter when it arcs up or down. It would then move the axle to the rear on compression when the shackles are in the front. Maybe Jeep figured that the stock spring was pretty close to flat when static.

 

What I always wanted to know is this: if you are driving on the street and take a left hand corner with your front shackle jeep, the jeep will lean to the right making the left springs shorter and right springs longer, which should turn you to the left without turning the steering wheel because the left tires getting closer to eachother and the right side tires are getting farther away.
Now reverse shackle the front axle, go around the same left corner, jeep leans right, the left springs get shorter, both moving forward , and right springs get longer, both moving to the rear , which now steers the jeep to the right without moving the steering wheel.
I guess my question is for the guys who have reversed shackled, is can you notice any difference in the steering, oversteer vs. understeer when you corner on the street? Or am I just a guy on a jeep forum typing confusing questions?

 

x3. Snake oil.

My JEEP had the start of a reverse shackle installation when I bought it, so I finished the job. It steers fine, but I've learned it has a lot more to do with bushings/bearings/castor than anything else (In my case, the jeep was undriveable with soft bushings). Really, though, leaning around corners is the least of your concerns.

My springs have a lot of arc in them at static. With good brakes, you will get brake dive with soft spring rates. With crappy brakes, say drums that don't grab at exactly the same time or force, you will be able to see your whole axle twist one way or the other if you lean your head out the door while you brake. Then you are tyring to play a fun game of counter-steering and pumping brakes at the same time. This may, or may not, add to symptoms such as random lane changes, road wander, etc.

I've got mine performing well now, but for the work involved, it gives me no more trail ability than almost identically equipped jeeps (Sparky, MOP) that have front shackles. YMMV, DAMHIK, IIRC, and all that stuff. If you notice, even later model jeeps that have coil setups use massive solid control arms mounted to the frame to keep the axle from flexing backward. There is a reason for this! The frame mounted main eyes on the stock front shackle setup have the same effect: they keep your front axle from slopping all around and making it a safety hazard to drive on the road.

The theory that it rides better over obstacles is a myth! At the end of the day, you are still sitting on an 80-something inch wheelbase with leafs. It ain't gonna ride soft unless you are avoiding the obstacles that make these jeeps so fun! If you want a soft ride, buy a TJ. If you want all-around reliability and safety, I would stick with the front shackle, if that's how your jeep was engineered originally.

 

To answer GPin's question, I had a set of YJ springs custom made to CJ length. I did a shackle reversal when I had the front axle out. My Jeep really drives nice where it drove like crap before. I think most of the improvement came from finding several things wrong with my frame and cross member. I found a number of small cracks and the rivet holding the front cross member to the frame was pulled through the cross member. This same rivet goes through the front shackle mount. I think most of the improvement I gained in how my Jeep drives is from all the issues I fixed but by the time I found them I was commited to the new springs and shackles. I am still very happy with how it drives and works off road. My Dad raced a 41 MB, 2X3 chassis, 327 small block back in the early to mid 70's. He mainly raced the Brush Run 101 in Wisconsin. Some of the race is very high speed if you have the gonads to do it. He reversed the shackles on his Jeep and found it more stable at high speed. I really think it's driver preference, but I like mine reversed. I am running drum front brakes so I don't notice much "brake dive".

 

Sorry, I forgot to add I stayed spring under.

 

I have thought about it a lot, pretty much doing what you did cj-john, to try and gain a better ride out of the front end, but honestly my jeep will drive down the freeway at 70mph with pretty much one finger holding the wheel, I don't think all the work to do the job on my jeep would be worth it right now, .... unless something was to break and give me the excuse to modify!

 

It was a lot of work. The width of the YJ springs made it a pain. I was at a point where I was ready to try anything to fix my road wander. I will say that it was well worth the effort. I had my Jeep out today and it is a joy to drive. We had it at the Badlands in Attica IN. a couple of weeks back and it really works great off road. I have a front sway bar and steering shock but I didn't install either when I finished. I wanted to see how much difference the springs made without them. I may use the sway bar later but I probably won't put the steering shock back on.

 

I think the steering shocks just add that much more stress to a frame that doesn't need any more stress, I pitched mine years ago. Seems to drive fine without it.
Glad to hear your setup works good cjjohn, You got a good looking Jeep!