V8 power + leaf springs = Squat, twist, shimmy.

Got a question for the suspension experts. I just (finally) got the computer dialed in. Turns out the chip was programmed wrong out of the box. It is running great! The builders (engine and intake) each estimated the power in the 325-340 range. I'm loving it. My suspension... less so.

I've got R.E. 4.5" springs and M.O.R.E. shackles - they add about 3/4". The Jeep has 2,800 miles and 2 years on it. So, the springs have settled a bit. And, I'm sure the 35s on 15" wheels add to that race car feel.

If you've ever driven a lifted CJ with a strong V8, you probably know what I'm feeling. Under hard acceleration, the Jeep squats and twists. So, when I lift off to shift, it "unwinds" and squirms around.

I'm sure a 4-link would solve all my problems... I'm wondering if there's anything short of that that'll help keep the Jeep a bit more settled. Oh sure, I could not romp on it... but what fun would that be

Thanks!

I just read your description and this is exactly what happened to me last Friday when I took her out and stomped on it... letting off it got a little loose and some white knuckles... I have to agree, the springs must have softened a bit from last year and that is causing it. I know I can't do a 4 link and will be interested to see what others have done to take the twist out of it.

cb

The Detroit locker you have in the back end does not help matters, especially with a standard transmission. The Detroit gets "spooky" when you come on/off the power, especially at speed. The inherent slack of the differential will cause handling issues.

My old CJ-7 had a built 304/T-18/Detroit in the rear rolling on 33's. It would get a bit "loose" when you would shift under hard power.

The Rubicon Express springs are too soft for a V8 and spirited driving at high speeds IMO. My red 6 cylinder powered Jeep has RE springs, and I can "torque" them some, and that is with an Ox Locker (open diff on the road).


My tan Scrambler runs a Detroit, 33's, TBI 350, but with an Automatic transmission. The automatic transmission makes a huge difference in how the Detroit behaves, especially at speed/shifting. No jerking/unwinding. It is almost invisible. This Jeep also runs stiffer Superlift 4" springs, and they keep the torque twist to a minimum, but at the expense of some comfort. I have drove this Scrambler north of triple digits, it handles good, does not get spooky, unless you get stupid.

Ahhh... didn't think about the Detroit contributing. Of course - makes perfect sense. In stead of...
- Eliminating the Detroit
- Swapping springs
- 3-linking it
- Fab'ing a pan hard (or other) set up
or
- Swapping for an automatic
... maybe the best bet is to drive it like the 7' tall lifted CJ that it is... and leave the tire lifting launches to the next toy

My CJ-5 is downright scary when I am on the gas. I put the fear of god in a few of my friends. I can still keep it under control but it is no Camaro that's for sure. You definitely need to treat it with respect or it will eat you alive.

It sounds like you need some type of traction bars to eliminate the axle wrap. There are several different kinds out there. For most, it's not an issue unless you're running a spring over setup.

I think your problem is spring wrap rather than the Detroit.

Let's start with the Detroit. It locks under acceleration/deceleration conditions, and is otherwise unlocked. Accelerating in a straight line will cause it to lock, and when you put the clutch in to shift, it will unlock. While you continue in a straight line, you shouldn't feel the Detroit at all. The axle shafts can/will bind when you accelerate/decelerate through a curve; ultimately this stored energy will escape, either by causing the tire to "chirp" (often happens in really tight corners while accelerating through the corner), or the next time you let off on the gas (and/or to shift) enough to transition from acceleration to deceleration, in which case the Detroit will unload that stored energy with a "BANG!" often associated with Detroits.

I've always found that with a manual transmission, the Detroit is very predictable. If I accelerate through a tight corner, it will lock and the tires will chirp. If I coast through a corner, particularly with the clutch in, the Detroit will just lightly click as it ratchets, but create no change in handling. If I'm on the highway and make a long sweeping turn, the next time I intentionally decelerate (or push in the clutch to shift), the Detroit will unlock and release the stored energy.

When I have driven automatic transmissions, I find the Detroit's behavior less predictable because I don't always know when the transmission will shift. I've found myself much more thrown-around by Detroits when installed with auto trannies.

Now, your "squat and twist" definitely sounds to me like axle-wrap. This tends to be less of an issue with SUA vehicles, but becomes more prevalent with increased torque/HP, brought on in your case by your healthy MPFI SBC 350. You'll probably find that your right rear spring pack has sagged more than your left, which is due to how the rotational forces transfer; this will also probably be the side that it squats/twists to more.

A four-link will solve this, as will a triangulated three-link. If you want to keep leaf springs, you will need to build/buy some kind of traction bar. There are many different theories about how to build them, why you should weld here versus there, etc. But one that is properly set-up should solve all your problems. If you are less concerned about trail manners (and flex), your choices are wider.

I know with my RE springs and Detroit in the back, it rear steers like a B***h in turns such as from stop signs or lights. With the body roll, it'll compress the outer spring enough to lay the bump stop on the axle tube. At that point, the outer spring gets longer(and the inner spring to the turn gets shorter from the front spring bolt) and the wheelbase changes easily a couple of inches from the driver side to the passenger side. Then add in the Detroit helping springs compress(bind) and it gets exciting if you don't predict that into tight turns.

You all should swap to the 258 ! Problem solved !!

I had the same issues with my rig as well. SOA, large v8. auto trans, and solved the problem with a sway bar up front and Currie Anti-rock in the rear. No more problems and easily disconnected for the trail.

My cj7 has a built 350 (320 hp) with black diamond 3.5" springs and 1" shackle lift. I have a limited slip and a automatic. I don't have the axle wrap problem, the black diamond springs are stiffer (you feel it at every bump). If I light the tires up (advantage of the v8) she is a bear to keep in a straight line. When the cj8 is complete it will have the same setup except re springs. Hopefully I won't have this problem.

I built a torque arm / traction bar for mine. It has kept my springs alive (2.5" RE, SOA, close to 400hp). If I kill these springs, I will 4 link the rear.

Bad Karma said:

I built a torque arm / traction bar for mine. It has kept my springs alive (2.5" RE, SOA, close to 400hp). If I kill these springs, I will 4 link the rear.

Click to expand...

Not "if", but "when"

AK-RWC said:

I think your problem is spring wrap rather than the Detroit.

Let's start with the Detroit. It locks under acceleration/deceleration conditions, and is otherwise unlocked. Accelerating in a straight line will cause it to lock, and when you put the clutch in to shift, it will unlock. While you continue in a straight line, you shouldn't feel the Detroit at all.

Click to expand...

My gut reaction as well.

I have an auto and nothing close to big HP, but the only time I ever notice my Detroit at speed seems to be after taking a somewhat gentle corner at maybe 35-45. Occasionally I'll get the Detroit bang out of it, happened just yesterday to let me know it was still there and made me smile.

If you're talking about straight-line issues, I can't imagine it's the Detroit. Turns are another matter entirely.

fixed that problem years ago with heavier springs and long add a leaf in my 7. its the cheeper way to fix it. hard ride but its a jeep.. i did bend main leafs before with softer springs.but yesterday i did load 1000lbs of concrete in the bed and it drove like a dream.. lol.. i made it over a steep bridge also .. try that with a 258... v8s rule!!