torque steer - out of idea's

[blistovmhz]

98 XJ, 6.5" LA lift, 63" chev leafs, 35x12.5r15 KM2, bilstein 51xx, OTA/OTK 1tonne steering, frame stiffened and braced, lunchboxed d44 and d30, RC long arms.

I've brought this up before but never found an answer.
I've got torque steer on acceleration and deceleration. 95% of the time it pulls left on accel and right on decel, but only with engine torque. Brakes keep me dead straight every time. The harder I torque, the more it steers. That last 5% of the time it'll steer the opposite. Right on accel and left on decel. I've never been able to determine what's changed just prior.

The brakes stopping straight rules out trackbar/draglink angle, which are dead parallel anyway and nearly the same length (same length ratio as stock at any rate).
Jeep almost always pulls slightly left on a cruise with very light positive torque. If I chuck it in neutral and coast, it's dead straight all day. Engine torque is the only thing that causes the steer.

Leafs are brand new and dead level. Problem was the same before swapping leafs. I originally thought the problem was caused by my old XJ leafs being raked back a few degrees, but the new leafs and mounting locations didn't change anything at all.

I've checked every joint a hundred times and measure my wheelbase for square. Steering self centres perfectly every time and front end is perfectly aligned (I'm positive on this). I've rotated the tires several times with no change. I've put a brand new tire on each side (one at a time to make sure my tires were NOT the same size) which changed nothing. I've tried airing up and down (I normally run at 30psi as I'm a 5000lbs rig). Control arm bushings and JJ's are all solid. I've disassembled them all for inspection and made sure they're tight. I've got only a very mild wrap considering the v8 power, and either way, adding in antiwrap didn't help. I even stuck on some 250lbs/in overloads and rode on them to make sure wrap wasn't the problem. No change.

As far as I can tell, the problem started when I threw in the rear d44 (with a lunchbox). This was before I did the 1 tonne steering.


There are a hundred threads on this, but the ones where the owner had ruled out all the obvious stuff, no solution was ever found (except in a few cases the guy would replace the locker and problem goes away). I understand suspension dynamics pretty well and I can think of a hundred possible suspension related causes of torque steer, but I've ruled them all out in my case. I'm pretty confident the issue originates at the locker but I can't figure out why and it seems like a lot of threads draw the same conclusion. I want to know why. SOMEONE must know right?

I'm wide open to suggestions. I ignore anyone who replies with "it's a Jeep, don't expect it to handle like a Lambo", but at the same time, I don't expect it to ride like a race car. When I say there's a suspension problem, I do mean it's a real problem. I daily drive it but I'd never let anyone else take it on the highway (other than my roomie, cause he's competent). Even being very familiar with the torque steer, I'm not entirely comfortable driving it at speed. If/when I need to speed up or slow down in a hurry, it'll torque enough to throw me right upside down if I'm not VERY ready for it. Constantly have to pull left during a cruise, and if I let off the gas, I have to compensate with the wheel every time. Really sucks when someone tries to rear end me or slams on the brakes in front of me.

So, who's ever found an answer? I feel like it's gotta be funkiness in the locker but I just can't imaginate the dynamics of what'd be going on.


P.S. The one thing I haven't tried is running smaller shoes. I'm guessing, if it's the locker, that bigger shoes will amplify the problem so smaller should make it less noticeable. May try that today, it's just a bit of a heat score running stock tires on my rig which is a heat score regardless .

 

[jonzer12]

Did you address your trackbar when you went OTK? When the rear squats the front will lift could be as simple as that. Make sure your rear tire pressures are balanced well. Also try running on just the front driveshaft to troubleshoot the rear end.

 

[scoobyxj]

It's your locker. Mine does the same thing, and it started when I installed the locker.

 

[blistovmhz]

Did you address your trackbar when you went OTK? When the rear squats the front will lift could be as simple as that. Make sure your rear tire pressures are balanced well. Also try running on just the front driveshaft to troubleshoot the rear end.

As mentioned, doesn't steer on braking, so it's not the front end. Can't be. I can almost get my front wheels off the ground with the new motor but it doesn't torque any harder at WOT than it does at 10% throttle, and zero steer with braking. ONLY happens when the engine is torquing the rear. I've run without a front DS as well (cause I had to break it off at the ear when my hybrid t-case started shitting itself, which turned out to be just an out of adjustment linkage ).
Running only the front, there is no steer whatsoever, but even if it was the front, with locked 35's and front wheel drive, it's goona wanna drive straight even if the suspension was pooched all over. I had to drive home in FWD down the highway. I'm not strong enough to make it NOT go straight.
Tire pressure has never mattered. I can run the driver on 10psi and the passenger at 40, or vice versa, and it doesn't affect how it pulls. Something in my Jeep REALLY wants to go left on accel (most of the time) and right on decel (most of the time), but only with engine torque. This has lasted through a complete front end build (from stock to what I'm running now), two engines (4.0L and 5.3L), two transmissions, 3 t-cases, at least 6 drive shafts, and two sets of tires (33's and 35's). The only thing left on my Jeep is the axles, lockers, and unibody (which is very well beefed up).
That said, I'd be very surprised if my uni was even remotely straight. I figure it shouldn't matter as when it's sitting on level ground, my suspension keeps the uni level as well and all square at all the important parts. Forward of the steering box is definitely way out, but all the important area's are square and true.

It's your locker. Mine does the same thing, and it started when I installed the locker.

Yea, that's the story I've heard many times. Problem of course is heaps of guys who say that think that they know everything so they don't mention that they also did some suspension work at the same time . Thus, when someone actually does nothing other than install the locker, no one believes them.
In my case I can't say with absolute certainty that this started with the locker, but I am VERY confident. Call it 99% confident that it started the day I installed the d44 with the lunchbox. That said, the lunchbox is probably very old. I'd imagine it was installed sometime around when lunchboxes were brand new. I'd just chuck another one in to test, but I hate throwing money at troubleshooting when theory could probably ferret out the answer. Also, I'm not super big on dumping any more money into either of my axles as I'm still debating going tonnes.

All I can think to do at this point is remove the locker and find some spiders just to test. I'm sure I don't have any for a 44 though. I suppose I can drop my roomies spare d35 on as a test when he's got his 8.8 back together. Assuming swapping to the 35 works though, I guess that rules everything down to the axle housing or locker, in which case a set of spiders would be nice to get the issue right down to the locker.

 

[scoobyxj]

As mentioned, doesn't steer on braking, so it's not the front end. Can't be. I can almost get my front wheels off the ground with the new motor but it doesn't torque any harder at WOT than it does at 10% throttle, and zero steer with braking. ONLY happens when the engine is torquing the rear. I've run without a front DS as well (cause I had to break it off at the ear when my hybrid t-case started shitting itself, which turned out to be just an out of adjustment linkage ).
Running only the front, there is no steer whatsoever, but even if it was the front, with locked 35's and front wheel drive, it's goona wanna drive straight even if the suspension was pooched all over. I had to drive home in FWD down the highway. I'm not strong enough to make it NOT go straight.
Tire pressure has never mattered. I can run the driver on 10psi and the passenger at 40, or vice versa, and it doesn't affect how it pulls. Something in my Jeep REALLY wants to go left on accel (most of the time) and right on decel (most of the time), but only with engine torque. This has lasted through a complete front end build (from stock to what I'm running now), two engines (4.0L and 5.3L), two transmissions, 3 t-cases, at least 6 drive shafts, and two sets of tires (33's and 35's). The only thing left on my Jeep is the axles, lockers, and unibody (which is very well beefed up).
That said, I'd be very surprised if my uni was even remotely straight. I figure it shouldn't matter as when it's sitting on level ground, my suspension keeps the uni level as well and all square at all the important parts. Forward of the steering box is definitely way out, but all the important area's are square and true.



Yea, that's the story I've heard many times. Problem of course is heaps of guys who say that think that they know everything so they don't mention that they also did some suspension work at the same time . Thus, when someone actually does nothing other than install the locker, no one believes them.
In my case I can't say with absolute certainty that this started with the locker, but I am VERY confident. Call it 99% confident that it started the day I installed the d44 with the lunchbox. That said, the lunchbox is probably very old. I'd imagine it was installed sometime around when lunchboxes were brand new. I'd just chuck another one in to test, but I hate throwing money at troubleshooting when theory could probably ferret out the answer. Also, I'm not super big on dumping any more money into either of my axles as I'm still debating going tonnes.

All I can think to do at this point is remove the locker and find some spiders just to test. I'm sure I don't have any for a 44 though. I suppose I can drop my roomies spare d35 on as a test when he's got his 8.8 back together. Assuming swapping to the 35 works though, I guess that rules everything down to the axle housing or locker, in which case a set of spiders would be nice to get the issue right down to the locker.

I didn't do any suspension work when I installed my Spartan. In fact I was sill on stock tires when I put it in. It does the exact same thing you described. It almost always pulls to the left when accelerating, but occasionally it'll pull to the right. It all depends on which side locks to the carrier first. Mine was really bad due to the excessive slop in the steering gear box. After I swapped in one with about 120 thousand less miles on it the condition remained, but it's not as bad. If you think about it it makes since. 90% of the time the passenger side tire is the one that does the work. If you power brake an open differential which side usually spins? When you get on a vehicle with and open diff in a right had turn it usually just spins the right rear, but if you do it turning left a lot of times it will actually break both tires loose, and you'll power slide.

 

[blistovmhz]

But most guys don't have the problem. I've never driven another locked XJ, but I know my roomies k1500 (8" lift, SAS, built it all myself, front/rear lunched), there is no torque steer at all and he's on 37's. If anything shouldn't go in a straight line, it's his truck. The SAS was my first attempt at any suspension fabrication beyond my 1 tonne steering. Entirely possible that the shorter XJ wheelbase plays a role, but again, most guys chuck a locker in and never mention the torque steer. There's something that a few of us are either missing, or we're just lucky and have pre-existing issues that are amplified by the locker.

The dynamics of a leaf sprung rear make sense for torque steer. On positive (forward) torque, the passenger side compresses more than the drivers. This causes the passenger side to move slightly back and the driver slightly forward, causing the rear to dogtail to the right, thus causing the Jeep to go left. Works the opposite direction on negative torque as well, so it makes perfect sense. The question is, is this enough to cause our issue, and if so, why don't most people notice it?

This was my line of thought with my old XJ springs. I had a shackle drop installed to get the lift I needed, so the rake of the leafs would amplify the dog tailing substantially, over what you'd see if your leafs were flat. Also, higher arch leafs will amplify the problem. This is why I decided to do the 63" chevy leafs. The longer leaf meant I didn't need as much arch to accomplish the same lift, and because I was building my own mounts, I could make sure the leafs were dead level instead of raked back. I was positive this would solve or at least decrease the torque steer, but it made absolutely no difference whatsoever. Thus, I have to assume that the dynamics of leafs under torque do not cause the dogtail necessary to cause torque steer ( my old leafs were PRIME for causing dogtail, but even that wasn't enough I guess ).

Inside the pumpkin, I can imagine that one side of your locker having teeth with slightly higher tolerance, could absolutely cause a very brief torque steer, as the wheel with the tightest teeth would grab a few ms earlier than the looser side, thus causing a very brief push left or right, but the steer is constant, so that rules out that. I even replaced my shafts because I figured the slight twist in the shaft splines may have contributed, but still no love. I've done everything but replace the diff housing and locker.

Actually, I guess I can kill a few birds with one stone by throwing my d44 into my roomies Jeep. His tracks straight and exhibits no torque steer, so this would completely rule out any suspension issues on my Jeep, if the axle causes problems in his Jeep. As he's running temporarily on the 35 until we rebuild his 8.8, I'm sure I can convince him (especially as I'm the one who has to setup his new gears) to run my axle for a test drive. he's got axle swaps down to about 30 minutes anyway .

I'll try swapping my axle to the other XJ and report back. Perhaps I'll be able to come up with a definitive answer once and for all.

 

[Demonoid369]

I'm wondering if it's tire pressure, with a locker under load, both are spinning. You say under no engine load it tracks straight, but under load it pulls. Maybe both tires at 30psi are NOT at the same height. It could be a matter of both suspension squatting and tire size that's causing it

 

[blistovmhz]

I'm wondering if it's tire pressure, with a locker under load, both are spinning. You say under no engine load it tracks straight, but under load it pulls. Maybe both tires at 30psi are NOT at the same height. It could be a matter of both suspension squatting and tire size that's causing it

Stuck a brand new 35 on one side. No change. Stuck it on the other side, no change.
That's a full 1/2" diameter difference, but it's not even noticeable on the street. Also tried lowering pressure on one side and increasing on the other, then swapping. No change.

Whatever it is, it's not tire size difference.

As for rear squat, perhaps, but I'd be surprised as the issue did not change at all after swapping out my entire rear suspension for a much better and completely different design.

 

[Brent T]

I've had two high hp cars and one jeep with rear lockers (Detroit's) and they've all done exactly what you're describing. Different vehicles, different rear suspension setups, same result. I've gotten so used to it I don't notice anymore.

 

[ehall]

would a traction bar help?

 

[blistovmhz]

Dunno yet, but I doubt it. Major changes in rear suspension didn't make any difference.

 

[civic50]

Have you checked the rear leaf eye bushings for the front perch? A deteriorated bushing allowing the axle to shift for and aft on one side only would cause your issue. Then I'd look into the front perches themselves... Any cracks on them could allow movement of the spring for and aft under power. Also are the u-bolts tight and not moving on the spring pack? Are you running OEM chevy packs or aftermarket? I've had the leaf with the bushing pressed in crack at the alignment pin but have the military wrap second leaf hold all together enough to allow the shifting without loosing the connection to the body.

 

[blistovmhz]

Hahahaha. Man, asking this question is like pulling teeth!.

I am absolutely certain that all of my bushings and connections are rock solid, and I am very confident (not positive, but very confident) that the problem is not due to suspension geometry.

The problem started around the time I installed the D44 and rear locker. I did the front locker later.
When it started, I was on 4.5" XJ springs. Switched to another set (for other reasons), then another, then added a shackle relocation, then another set of XJ springs at 6.5", then the 63" chevy leafs (3.5" lift springs from ProComp) and rebuilt all my mounts in non-stock locations. On the front, I've gone from stock steering to 1 tonne OTK/OTA. All my brake calipers have been replaced/upgraded and there is no brake drag. If I hold the front end down with a tie strap, to prevent the front suspension from lifting, there is no change.
The front leaf perches are 1/4" plate welded to the 3/16" stiffeners over to my 3/16" rectangle tube sliders. The holes are so tight to the bolts that I need to nudge them through with a hammer. The leafs themselves (which have been switched at least 4 or 5 times since the problem began) are in perfect condition.
The front joints are all rock solid. I've torn them apart multiple times for inspection and tightened the crap outta the johnny joints. Bushings are all perfect. I've honestly never seen a built XJ as tight as mine is now, after years of trying to track down this torque steer issue.
The wheels and axles are all square to each other. I've also intentionally taken them out of square in both directions as well as shifted the front axle to the left and right to see if I can make the issue better or worse. No change.

The ONLY possibilities I can come up with are:
1. Locker is locking at a weird time.
2. Some complete unknown in the D44.
3. Unibody is twisted (though I can't figure out how this would matter as I've blocked the axles to the uni to remove any supsension flex from the equation).
4. Rear axle dog tailing. I'd seriously suspect this except that the problem didn't get worse with the v8, nor with the much softer chevy leafs, and it's no worse when I hammer on the throttle or feather it. ANY torque at highway speed, causes the steer. I suppose it's still POSSIBLE that this is the problem, but when I did the 63" springs, I even tried leaving the overloads on (250lbs/in) which I was sitting right on (cause my rig is heavy). 250 extra lbs/in making no difference whatsoever, makes it extraordinarily unlikely that the leafs are the issue.

Either way, I'm going to drop the 44 into my roomies Jeep (which has no TS) to see if my axle will cause it in his Jeep. We're in the middle of rebuilding his 8.8 anyway, so the 35 will have to come off next week for the swap anyway, and as I'm the one setting up the gears, I'll call the extra swap payment for my time

I understand that most people are idiots, and no matter how many times they insist they checked A or B, they probably actually didn't but are just so sure it's not the problem, they'll never check. I however, don't do that. I want the problem resolved, and as I've tried everything I can think of, as well as everything everyone else has ever thought of (other than just removing the locker from the equation), I'd have no reason to make shit up .

 

[Demonoid369]

Obviously it's when both axles shafts are locked so one side or the other is off. Regardless if you think that both sides are spot on.

 

[blistovmhz]

Quite true. The question then becomes "is the locker locking up too early"?

If everyone had this issue, I'd just concede that this is just how lunchboxes work, but the issue is that the symptoms don't affect everyone. I've a couple theories as to why.

1. Leaf stiffness. One thing that's remained somewhat constant since the installation of my d44/locker is my Jeeps mass, and the spring rate (roughly). My Jeep is much heavier than most rigs and thus requires either a higher static spring rate, or a larger spring arc. The first leafs in there were some RE 4.5" springs (combination leaf and shackle). Fairly large arc and thus around a stock spring rate. Perhaps the extra mass sinking that stock-ish spring rate causes more than normal wrap on the passenger side, which would account for the TS. However, I've since tried much softer and much stiffer spring rates as well, with no obvious affect. The current 63" springs are 200lbs/in which is substantially stiffer than stock, and each leaf is much thicker than stock, so it is much more capable of preventing axle wrap than a stock leaf pack. My wrap currently is about the same as other rigs I've seen with stock length, stock thickness leafs, but with a military wrap (effectively doubling the anti-wrap of the main leaf). Thus, a military wrap wouldn't solve this on my Jeep either.
That said though, I've done a lot of testing on this theory and haven't been able to make the problem better or worse by stiffening or softening the leafs.
2. Total lift. With greater lift comes, usually, greater spring arc. Greater spring arc results in more rearward movement of the axle on compression, which should amplify any dog tailing. Again, I don't think this is my issue though, as my leafs are nearly flat at ride height (I can get away with this because the extra long leafs allow WAY more articulation before flexing upside down. Essentially for every inch of vertical travel on a stock pack, I get about 1.6" with the same arc. My stock length packs all had substantially more arc than I've got now, and the problem hasn't changed at all.

I sorta discount the possibility of the axles being out of square because I've measured it a thousand times from a thousand different angles. It's always spot on. I've pulled the unibody sideways with another truck and measured again. If one of my axles is out, it's only when under load, and it's being caused by magic. Even stuck a camera under there to watch and everything looks perfect.

Again, you're right that something isn't square when the shafts lock up, but if something isn't square on my rig, it's definitely no square on any other rig. No one has put the amount of time I have, into measuring the shit outta their rig. The question then comes back to, why do I have TS and others don't, and all I can think is that their axles aren't locking up under the same light duty conditions that mine is.

 

[ehall]

I'd guess its the mechanics of the locker, one side engages first and that's all there is to it

 

[blistovmhz]

I'd guess its the mechanics of the locker, one side engages first and that's all there is to it

But doesn't affect everyone. Thus, either some lockers are broken, or we all have something else in common with regards to suspension. That's what I'm trying to figure out.

Roomies k1500 with 8" lift doesn't do it, and that's way more leaf arch than I've got.

 

[GordoSmasho]

A quick way to test if it is the locker, pull the lunch box and put open spiders back in. Test drive for a week and get some miles on it open. If it changes then thats your answer. Might want a selectable for the rear.

I have a detroit in one of my rigs and it does exactly what you are saying. Ill be switching to a selectable when the time is right for an axle swap.

 

[blistovmhz]

So been too busy with roomie Jeeps (had to buy an XJ for the girl because she refuses to check her oil, and roomie blew up two pinion bearings on two different axles because he installed a JY 8.8 and didn't check the oil...) so I haven't had a chance to pull the locker for a test.
Last night though I got around to re-checking my thread depth for the hundredth time, and I dunno if I was just retarded before, or imagining things now, but my rear right tire seems to be a bit bigger than the rear left. Rotated in an X pattern and took it for a very brief test this morning on my coffee run, and didn't notice any torque steer whatsoever. I need to get it up to highway speed, but I may, embarrassingly, have solved the problem. :|
Will report back tonight.

Incidentally, the difference in tread was VERY minute. Not enough to really notice on visual inspection, but tread depth tool did show the right being deeper than the left, which would make sense in my case. Larger tire on right means right circumference is larger, thus moving faster per revolution than the left. This would definitely cause Jeep to go left on accel and right on decel.

 

[peterjford]

If it was the tread depth, please report back and let us know, I hate it when someone has a difficult to diagnose problem and then suddenly the thread stops. Its like watching a really good mystery movie and the it stops right before everything is revealed.

If it isn't the tire size I thought of 2 things to check that you might have already, but I haven't seen them mentioned. The first is the engine and transmission mounts. They should not cause torque steer, but make sure your engine/transmission isn't moving and pulling something else out of alignment. The second thing is the centering pins from the rear leafs could be bent or loose. That could cause the axle to move a little even if the u-bolts are tight and the leafs themselves don't move where attached to the frame.

Good luck.