weird handling with lift

ok, i'm not real sure what my problem is, but i can describe it very well. some say its death wobble and others say its something else; what's everyone's oppinions?

Ok, its a 99 xj with 6 inches of lift, 35x12.50 bfg's on 15x8s and I seem to have this really strange shake in the steering wheel when i go over a bump. Its a violent left/right movement, but just about an inch of movement and then it settles down. It's pretty easy to hold on to the wheel when it happens, but if you let the wheel go, the vehicle goes straight, wheel does its thing and its doesn't seem as violent. Also, when I steer in any direction, it takes forever for the wheel to center up if I let the wheel go. Like it doesn't want to center, but the forward movement of the jeep makes it. And when i brake, it pulls hard to whatever side the wheel is turned from center at the time. Like if I'm turning left, it pulls hard to the left when i brake; if its to the right, it pulls to the right.

I'm not sure what it is, I had it aligned and they said it was good toe in and good castor angle, but I have a feeling this guy was full of crap. I didn't request the print out in time, so I couldn't see the angles, but I have a feeling the castor is off. How do I know? would the castor angle cause all those problems?

I have been told to check my steering damper and I haven't changed it yet, but I somehow don't think its the problem, but who knows? Is 116K miles good for the stock damper, lol? I doubt that it's still good.

Any ideas/thoughs would be awesome, thanks guys.

what are u running for a Track bar

Search "death wooble". You'll find lots of info on it. You'll know if you have death wooble or not. I just have a shimmy most of the time, but the first time I had death wooble, I was about to shit my pants. You literaly think your front axle is just going to fall off.

well, I thought it was death wobble too, but its no the "oh shit! my axle just fell off" fleeling, just a weird movement of the steering wheel.

I'm running a FT track bar. Came with the kit.

does it only happen when the suspension is flexing (pot hole, speed bump)

im not anyones expert but what type of lift? didi you use new longer lca's or drop brackets? just from reading here the past 6 or 7 months i've learned all kinds of tricks for checking camber and learning what to look for when lifting especially on a budget). try a search for deathwobble too see what uyou find. after reading these guys favorite phrase i tried it and yes it does work sometimes.

Yes, it only happens when the suspension is flexing, ie, pot hole, speed bump, crack in the road.

Its a FT 6in Long arm kit btw. it relocates the arms to the rear, forward of the crossmember. The lower arms are around 33 inches i think.

Guys...the poster is used to CH-53s...DW to us is probably just a normal in-flight vibe to him

My first guess would be that the alignment was fawked. Was it a lifetime type of deal, or a one-time thing? Also read up on DW at http://www.yuccaman.com/jeep/dw.html

Semper Fi,
Jim

If the steering stailizer is not inline with the TR or DL it will not function as effectively.

Have some one slowly turn your wheel back and forth just enough to look for movement at either end of the trac bar. This is a common cause of deathwobble. If you had no stabilizer you would have the falling apart feeling like I had last week before I put on the stabilizer. Now it's really only a problem at 40MPH.

Yucca-Man said:

Guys...the poster is used to CH-53s...DW to us is probably just a normal in-flight vibe to him

Semper Fi,
Jim

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Hey Semper Fi Jim! Lol, yeah, pretty used to a rough ride, but man, those 46's are a peice! Lol, now that's a vib!

I'll have to look at that track bar and see if it does move. Its the 1st, so I just got paid and am gonna be purchasing a new stabilizer, so I'll let you all know if that fixes it. Thanks for the imput guys.

What you describe with steering when you hit a bump, sounds like you may have some bump steer.

Do you have a drop pitman arm?
Are the angles of your track bar and drag link similar? In a perfect world, they run parallel. If you have the stock pitman and a 6" lift, they prolly are not anywhere near parallel and a 1" or so drop pitman should help. BTW replacing the pitman can be a major PITA so you might want to talk with a good alignment guy (not a tire store chimp) first.

Your problem with the steering not wanting to return to center may be a symptom of wrong caster angle. At 2 degrees caster, mine does that bad and is fine when set at 4 to 5. Factory spec for my '91 is 7 to 8 degrees. With a big lift, you have to compromise between your pinion angle and caster angle. If you set caster to factory spec, you might then get front driveshaft issues with the yoke binding.

Aren't lifted XJ's fun? :wierd:

I have a full-traction 6in long arm also and i am feeling the same thing going on. It steers odly when i hit a bump. The guys at ORW aligned it and said that what i was feeling was torque steer because of the front end rising up when i am on the gas and dropping when i am on the brakes. it felt out of alignment to me before they worked on it again. Im not sure if that really is the problem or what. does that sound right to you guys??


and i have the full-traction steering stab on it and it helped a little after i installed it

jonboy said:

What you describe with steering when you hit a bump, sounds like you may have some bump steer.

Do you have a drop pitman arm?
Are the angles of your track bar and drag link similar? In a perfect world, they run parallel. If you have the stock pitman and a 6" lift, they prolly are not anywhere near parallel and a 1" or so drop pitman should help. BTW replacing the pitman can be a major PITA so you might want to talk with a good alignment guy (not a tire store chimp) first.

Your problem with the steering not wanting to return to center may be a symptom of wrong caster angle. At 2 degrees caster, mine does that bad and is fine when set at 4 to 5. Factory spec for my '91 is 7 to 8 degrees. With a big lift, you have to compromise between your pinion angle and caster angle. If you set caster to factory spec, you might then get front driveshaft issues with the yoke binding.

Aren't lifted XJ's fun? :wierd:

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Yes, I do have a drop pitman arm of 1 inch. yeah, it was a PITA to take off, but at work we have some amazing tools to do similar jobs on helocoptors, so it wasn't too bad. Yes, the tie rod and the drag link are very close to being parrallel.



As far as the castor angle goes, i'm not worried about driveshaft angle as i'm getting a high flex joint from tom woods to put at the pinion and it shouldn't be any problem. Or do you all think that isn't the way to go?

My initial quess is you don't have enough caster, your response of slow to center indicates that to me.

Also, when I steer in any direction, it takes forever for the wheel to center up if I let the wheel go.

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You can check your caster yourself. It's not as accurate as being on a rack but will tell you if the allignment shop got it close or not. Take an angle finder and place it on the flat side of the diff cover.

• HP Dana 30 9 - differential cover angle = caster angle.
• LP Dana 30 12 - differential cover angle = caster angle.

ideally you want 6.5*. adjust it, you can always set it back where it was.

Rock Yacht has the right idea... Use an angle finder to find out what your caster is. Personally I check mine on the top ball joint. You should have 6-7* positive caster. Your toe in should be 1/8 of an inch.


The problem you are describing definately sounds like bump steer. I dont know how to tell you to fix it, cause I changed my whole steering set-up to get mine right.



Patrick

What kind of backspacing do you have on the wheels? Changing from stock too much can throw off the scrub radius(easier to internet search than to explain). This could cause it to pull to the side that you have the wheel turned to, amongst other handling problems. With incorrect castor the problems are amplified. My stock XJ also seemed to do what you describe over bumps, although I didn't think it was violent.

Rock Yacht said:

You can check your caster yourself. It's not as accurate as being on a rack but will tell you if the allignment shop got it close or not. Take an angle finder and place it on the flat side of the diff cover.

• HP Dana 30 9 - differential cover angle = caster angle.
• LP Dana 30 12 - differential cover angle = caster angle.

ideally you want 6.5*. adjust it, you can always set it back where it was.

Click to expand...

What do you mean by the flat side of the diff? I'm not sure I understand WHERE to take the measurement. What I think you mean is the front, to the left or right of the diff cover (where I got my rear axle angle from) and then subtract 9 from that to get my angle.


As for the BS, I have 3 3/8" BS. I wouldn't say what I'm feeling is violent either, that's why I am confused when people say it is DW, because it's not a violent motion, just going over cracks in the road, bumps, whatever, it moves my wheel left then right of center or right then left of center. Not enough to rip from my hands but enough to be annoying.

Now if my problem is bump steer, how is that fixed? As I understand, bump steer is caused by you're steering geometry, so I'd have to change my steering set up to correct? And I'm assuming that if it is bump steer, the wrong castor angle would multiply the problem. Would it be possiable that it is only the castor angle that is the issue, causing it to seem like my steering geometry is wrong? Just some thoughts.

53guy said:

What do you mean by the flat side of the diff? I'm not sure I understand WHERE to take the measurement. What I think you mean is the front, to the left or right of the diff cover (where I got my rear axle angle from) and then subtract 9 from that to get my angle.

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This is how I check mine -- magnetic angle finder from Harbor Freight and a piece of steel (so the angle finder will drop below the tie rod) against the two side bolts on front of the diff cover. I then use the same calculation posted by Rock Yacht.



If you can find a "real" alignment shop in your area, like one that does work up for SCCA or Porsche club racers, they should have at least one mechanic that can diagnose and recommend the right fixes.

53guy said:

What do you mean by the flat side of the diff? I'm not sure I understand WHERE to take the measurement. What I think you mean is the front, to the left or right of the diff cover (where I got my rear axle angle from) and then subtract 9 from that to get my angle.


As for the BS, I have 3 3/8" BS. I wouldn't say what I'm feeling is violent either, that's why I am confused when people say it is DW, because it's not a violent motion, just going over cracks in the road, bumps, whatever, it moves my wheel left then right of center or right then left of center. Not enough to rip from my hands but enough to be annoying.

Now if my problem is bump steer, how is that fixed? As I understand, bump steer is caused by you're steering geometry, so I'd have to change my steering set up to correct? And I'm assuming that if it is bump steer, the wrong castor angle would multiply the problem. Would it be possiable that it is only the castor angle that is the issue, causing it to seem like my steering geometry is wrong? Just some thoughts.

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there's a casting index circle on either side of the differential cover. Clean it off and place your angle finder on the face of that circle or set a straight edge across some differential cover bolts and place the angle finder on the straight edge. The most accurate would be to remove the driveshaft and measure off the machined face of the pinion yoke. Any of these methods should be accurate enough for driveway mechanics. In either case, you will get a reading in the 80° to 90° range.

Lo Pinion XJ D-30: your reading minus 80.5° = castor angle
Hi Pinion XJ D-30: your reading minus 77.5° = castor angle

5 to 6 is a good positive castor setting for a lifted Cherokee.

Backspacing will change your scrub radius, but taller tires do too. Most guys run wheels with lower than stock backspacing which increases scrub radius along with taller tires that decrease scrub radius. These opposing changes tend to cancel each other out for a low net change in scrub radius.

The steering problem you experience under braking is due to roll steer. The steep control arm angles add steering angle to the axle when the chassis rolls to one side or the other due to normal steering input. This is made even worse by the low castor setting. The cure is to reduce the control arm angles with drop brackets, repositioning the mounting points on the axle or switching to radius arms.

The shake you are experiencing at speed is the beginnings of DW. Left unchecked, things will only get worse.

Solve the control arm angle problem, set castor to 5° to 6°, replace your stabilizer. Then track down and resolve any slop in your suspension and steering joints and components. The track bar is one of the most likely problems

MaXJohnson said:

The steering problem you experience under braking is due to roll steer. The steep control arm angles add steering angle to the axle when the chassis rolls to one side or the other due to normal steering input. This is made even worse by the low castor setting. The cure is to reduce the control arm angles with drop brackets, repositioning the mounting points on the axle or switching to radius arms.

The shake you are experiencing at speed is the beginnings of DW. Left unchecked, things will only get worse.

Solve the control arm angle problem, set castor to 5° to 6°, replace your stabilizer. Then track down and resolve any slop in your suspension and steering joints and components. The track bar is one of the most likely problems

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Ok, I have the FT Long arm kit, so I don't think my control arm angles are affecting anything seeing how they're relatively flat. When I get that protractor back from work, I'll check my castor angle. Thanks for those numbers, those seem a bit more like the numbers I'd be getting. I'll check on everything else and update. Is there any difference in steering stabalizers? Would a rancho SS work the same as a skyjacker SS?