Smart suspension guys please help!

ltrpilot9

ltrpilot9

Well-Known Member
Joined
Oct 15, 2012
I have a 94 Jeep Wrangler, with 6" lift pro comp unileaf, trac bars still installed and 37" tires with a stock wheel base. I run a D44 from a 77 Waggy in the front and an 8.8 from a 95 explorer in the rear, 4.88 gearing in both ends. The problem is not something that is easy to describe. At certain hi-way speeds that vary from 55-70mph the jeep will at random times become very unstable. Sometimes its as bad as a sudden un-commanded lane change, sometimes its a minor wander. Sometimes it pulls a little to the right, sometimes not all all. It's nothing like a death wobble, its not a vibration, I hope that makes sense. It does not do it all the time, it does it most frequently when I let off the gas, and it almost feels like the rear end is swinging back and forth like it does when you do a burn out in a car. I have taken it to several shops, and all of them have claimed to fix it. They have told me it needed new tie rod ends, a steering stabilizer, a bigger trac bar, and lots of other crap. I did put new tie rod ends on it, had it aligned and its still just as bad as ever. All I can think is that it might need new leaf spring bushings, other than that I am out of ideas. Any help please?
 
Best bet is to get under it and try and move shit. If it moves and it shouldn't replace it.
 
U-bolts are the first thing that come to my mind. Make sure they are beefy 5/8" units and tight. Very tight.
 
Chris_Keziah said:
Best bet is to get under it and try and move shit. If it moves and it shouldn't replace it.
Click to expand...


What he said, get someone to turn the wheel back and forth a 1/4 turn in both directions, with the steering stabilizer disconnected. Grab the drag link, tie rod track bar, shackles, and etc when the steering is being cycled. Also check your ball joints, those being worn out can cause some wondering.

Edit: technically you should feel no changes running without a steering stabilizer, it's only meant to dampen movement and can hide a bunch of issues. I'm thinking more than likely your TREs have some wear but your ball joints are causing a lot of the wandering. Probably grabs the lines on the roads and takes you for a ride a lot.
 
Thanks for the replies, I spent all morning with the Jeep on the lift, and I am truly stumped. I can't find anything wrong with the suspension or steering at all. I checked everything mentioned above, and a0, ll I can find is that leaf spring bushings are a little dry rotted. I took it for another road test a few minutes ago, and have some more detailed information. First, it does have new TRE's and a fresh alignment, so its doesn't pull and goes perfectly straight down the road at a steady speed. Things get interesting when you let off the gas. If no steering input is made the jeep will dive to the right as soon as power is removed and change lanes in less a second. I experimented a little bit more and noticed that if you push in the clutch before you let off the gas it doesn't do it, only when you let off that gas with the clutch engaged. Also, it doesn't do it nearly as violently unless you are at hi-way speed. it starts at about 55, and gradually gets worse, the fastest I did it was at about 70and at that speed, its border line uncontrollable. Now, I am wondering if I have a problem in the rear end. Thoughts?
 
Make sure all your tires have the exact same psi.

I see you had the alignment just done on the front, what about the rear axle alignment?.

Make sure it's square with the front axle. Within 1/4" of front. Also check both axles squareness with frame. Tape measure will suffice from similar points on both sides of axles and frame.

Does it pull/push the opposite direction when applying the brake
Pedal?

X2 on locker in the rear?

Leaf spring bushings and shackle bushings in good shape?

Does it push left on the throttle
And then right on deceleration? Or vise Versa?

As well you can check your circumference of each tire.

Make a mark on the side wall of a tire at the very bottom and on the concrete/asphalt below it. Move the jeep forward or reverse one complete tire revolution, and mark the concrete again where the line on the tire meets the ground again.

Measure this distance and note it. This is the circumference of the tire with weight on it. Make sure all 4 tires have the same distance "rollout". Adjust air pressure to make all of the circumference of each tire the same.

If this means different psi for each tire keep track of changes and write them down.
 
Sounds like axle wrap. Maybe one spring a bit weaker.
 
As posted above, if you have a rear mechanical locker and the tires are not the same rolling radius then you can get this phenomenon. One side of the axle is "loaded up" and when you brake or otherwise change something it releases and shoves your vehicle to one side. By letting out on the clutch you release the bind from the driveline side so you do not experience the issue. You may end up having to swap tires around on the vehicle to find the pair that match the best. The last new Detroit locker I purchased (back in 2004) came with a small book that detailed how to get your tires matched best.
 
Damn, guys that is some genius shit! First, it's a posi-trac rear end, so not locked per-si. To further define what it's doing, as I let off the gas, the jeep dives right, the faster the speed, the more violent the movement. As soon as I step on the gas, it does track back to the left, and then its a balancing act to get it to straighten out. I can feel the chassis shifting weight from side to side as I steer and counter steer to keep it going straight. I also forgot to mention that I can hear and feel a distinctive clunk coming from the rear end as I let off the gas and get back on it. I don't know if that is related to the issue or not. It has brand new U Joints, which is what I originally thought the clunking sound was. I have already checked the track bar for any signs of movement, but I hadn't removed it. I will try that and see if it helps. I never would have thought that it could be a tire circumference issue. I will test them and make sure that they are all the same. Just thinking through the problem, that really seems to make sense. I really appreciate the advice, I hope I can figure this out soon.
 
Update. This is embarrassing, but if my humility saves someone else this trouble, its worth it. As advised, I checked the circumference and tire pressure in all my tires. The circumference was within 3/8" all the way around, but I matched the tires up and re-mounted them. I should have checked this first, and I can't believe I didn't, but the problem turned out to be due to air-pressure. I normally run about 30 psi in my tires on the road. The right rear was 70PSI. I sincerely have no idea how it got that much air in it, maybe my young son was practicing his mechanic skills, or maybe it was a prank from somebody at work. In any case, with the proper PSI, it is driving straight again. Thanks everyone for the advice, I hope you all have a good laugh at my expense, I deserve it.
 
normally it's to simplest fix does the job lol
 
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