Car "hopping" in tight turns

[EricCR]

Hey folks,

 

Another one: My GF has been using the Pathy and she told me the car was shuddering or bouncing when turning in her office's underground parking which requires fully turning left and has a smooth, slippery concrete floor. I was able to reproduce the issue today and it feels as when the center diff is locked, but the car is in 2WD mode (my R50 has the regular part-time shifter). Weirdly, it doesn't happen all the time and it's easier to reproduce the faster you are going ("faster" being relative here, say, 10mph instead of 5mph). It's a smooth, wavy motion, nothing harsh. The moment you let go off the steering wheel's full lock, just a bit, the hopping is gone.

 

In normal driving the car feels perfectly fine. I've read plenty of similar threads in other 4x4 forums and people say it's either a serious thing or completely normal, so I'm stumped. This is the closest I was able to find in a 4Runner forum: https://www.toyota-4runner.org/4th-gen-t4rs/234115-slow-sharp-turn-slip.html

 

Is it normal?

Edited February 16 by EricCR

[Strato_54]

I'm going to say this is normal because my parents are the original owners of my 97, and when I started driving it my dad always warned me about taking corners too fast for that reason. Since getting some Offset wheels and the lift there is no more of this wheel hop at all. My dad would say it was always on the right hand turns it would hop the most for him. 

[adamzan]

My Xterra has done this forever... I think it is a normalish thing for solid axle part time 4wd vehicles.

[Slartibartfast]

I'll bet this is a quirk of the Ackermann angle. When you're turning, both front wheels follow curved paths, but the inside wheel follows a tighter curve, so it has to steer sharper. The geometry to make this happen is built into the knuckles (where the tie rod attaches vs where the knuckle pivots). The farther you turn, the more the Ackermann kicks in. This also means that any error in the geometry will show up more the farther you're turned. Anything suspension-related tends to be at its worst at the limits of its travel anyway. I'm guessing the steering angles at full lock don't quite agree on how tight of a turn you're taking, which means one wheel or the other has to slip, which is more dramatic on the polished concrete than it is on normal road surfaces.

 

Strato's wheel offset is an interesting wrinkle to this. Changing the offset wouldn't change the angles, but it would change the curve of the paths they're on--evidently enough to get them closer to where the wheels are pointing.

 

Now that I'm thinking about it, I don't think I've ever driven mine in a parking garage, but I have noticed that it disturbs gravel more at full lock. Probably the same thing going on.

 

In any case, Ackermann is not adjustable (apart from racecar stuff), so I'd file this one under It Just Does That.

 

It's also possible I'm full of crap. But if you're not in 4x, then it's not torque binding. If a tire was hitting something in the wheel well, which would make sense with it only happening at full lock, I imagine you would've noticed the noise or seen the shiny spot. I've heard of the rear limited slip chattering if it's got the wrong lube in it, but I wouldn't expect that to only happen when you're against the steering stops.

[EricCR]

Thanks guys! Last night I noticed something else (perhaps since now I'm paranoid about full lock turns): Turned left again and instead of hopping, I got a noise that I can best describe as a low-pitched grinding noise, like a wheel bearing, but intermittent (linked to wheel speed). I jacked the car up this morning and it doesn't seem the bearings are bad, but then again, I can't put the lateral stress of a full lock turn when rotating the wheels by hand. The noise went away after warming up and driving a few min (I tried a couple more times). I also engaged 4L on a straight stretch to make sure everything got lubricated.

 

Could this be related to said hopping? The noise didn't correlate with any weird behavior, it wasn't felt through the steering wheel or chassis.

[Strato_54]

The rear drum brakes do rub ever so slightly, but I'll only ever hear it if i'm sticking my head out the window and really trying to listen. You'll always have slight shoe/pad rub and it will make a faint scrubbing noise that you otherwise should not hear INSIDE while driving. If you have an LSD in your pathy then that would help explain for the wheel hop/kicking when turning full lock. LSD's can cause wheel slip if they're too tight or the conditions are just right, but even on my open diff pathy I've felt this before.

 

If you have no vertical, horizontal play or binding in your bearings theres a good chance theyre probably good. Paranoia can lead you to thinking the worst but at the end of the day its all mechanics, and even my elbow at 20 makes some grinding sometimes lol

 

 

 

On 2/17/2024 at 10:21 PM, Slartibartfast said:

Strato's wheel offset is an interesting wrinkle to this. Changing the offset wouldn't change the angles, but it would change the curve of the paths they're on--evidently enough to get them closer to where the wheels are pointing.

 

My theory behind this is the wider stance gives it more "leverage" to keep the wheel down and planted on the ground. But since doing the lift I've realized the AC 2" coils are stiff af. With having less front corner dive around corners it wants to keep that weight over that opposite wheel, my pathy feels like a race car around some corners even with the lift. I'm also not as wide as most R50 though only running a -6 offset no spacer.

[Slartibartfast]

RE the noise, my first thought is the power steering pump, which is loaded when it's up against its stops. Could also explain why it calmed down once the fluid warmed up. Wouldn't explain the wheel speed connection, though, unless it's just the higher engine speed spinning the pump faster. Wouldn't hurt to check fluid level and condition.

 

Steering angle shouldn't be changing the load on the wheel bearing by enough to matter, not at those speeds. I would be looking for CV axle binding issues (unlikely if the truck isn't lifted) or tire clearance issues before suspecting the bearings. Might also take a look at your steering stops. I don't know how the R50 does its steering stops, but mine are metal on metal (they used to have plastic caps, but those are long gone) and now and then it'll creak like a haunted house at full lock. I just gob a little grease on them whenever I'm under there.

 

I wouldn't expect the leverage to play into the hop, but I guess the harder coils might be changing how the system resonates? Control arm angles from the lift might be factoring into it too. Or even the tires, assuming you're running different tires with the new wheels. Maybe some combination of the compound/tread pattern/sidewall stiffness just doesn't hop like the other tires did?

[EricCR]

Thanks for the tips. The more I think of it the more I recall previous instances of that humming when turning which then I attributed to tire noise or road imperfections, but it's clearly something else. The rear drums do stick a bit, especially when cold, so that's my prime suspect. I recently took the front brakes apart to do some cleaning and maintenance so I'm fairly sure those are fine. I did notice that the pads are missing the squeal shims, never installed by the PO.

 

I've read about the steering stops but people who report that describe a different noise, more of a metal-on-metal grinding instead of my low-pitched "hum-hum-hum".

 

My fear is something that's not properly lubricated in the 4WD system or a center diff lock that's not fully disengaging (if that makes any sense at all). That would explain both the occasional noise and the hopping. I'll triple check fluids yet again but I worry this is one of those things that will have to get worse to really be able to tell exactly what's going on.

[adamzan]

Steering stop noise doesn't apply to the r50, that's a wd21/22 thing.

[CALPATHY]

Mine "shudders" in really tight turns going slow when the manual hubs are locked, in unlocked mode it doesn't do that.

Edited February 21 by CALPATHY

[Slartibartfast]

CV axles binding?

[CALPATHY]

5 hours ago, Slartibartfast said:

CV axles binding?

It has always done that, so I don't think so.

[XPLORx4]

First, let me ask the obvious: do you have oversized/wide tires, heavily offset wheels? Are they rubbing anywhere at full lock? I know that on my 97 R50, at full right steering, my right front tire's shoulder lugs may rub on the fuel line cover and it sometimes feels as if it shudders. Check for potential rubbing.

 

Do you have strut spacers? If so, how tall are they? Are the CV axles at very high angles? Boots and joints in good condition?

 

If you have a rear limited slip, how tight is it? The wheel hop could be due to that. Since you have the part-time lever-operated transfer case, it has no center diff. It's either engaged (in 4H/4H) or disengaged (2H). Assuming your transfer case is not still stuck in 4H even when the lever is all the way forward, any scrubbing or wheel hopping in the front wheels could be due to potential damage in the front diff or something else that is disallowing the front diff gears to rotate freely.

Here are some things you can try to better isolate the potential causes:

1) Test rear driveline. Transfer case in 2H. Raise one rear tire off the ground by less than 20mm. Start engine, release parking brake, press brake, and shift transmission from Park to First gear. Release brake slowly. Do NOT apply throttle. Does the wheel in the air spin or does the truck seem to want to lurch forward? Lurching indicates a tight rear limited slip which could contribute to shuddering during tight turns. Consider this normal.

 

2) Test transfer case, front differential, front driveshaft, and left CV axle. Transfer case in 2H. Engine off, trans in Park, parking brake on. Lift left front wheel of the ground. Spin left tire. It should spin freely without binding, and front driveshaft should spin. Turn steering both left and right full lock and feel for any binding at inner and outer CV joints, front driveshaft u-joints. Any binding will contribute to the issue.

 

3) Test front differential and right CV axle. Transfer case in 4H. Engine off, trans in Park, parking brake on. Lift both front wheels off the ground. Spin right tire. Left tire should spin in the opposite direction without binding. Front driveshaft should not spin. Turn steering both left and right full lock and feel for any binding at inner and outer CV joints of right tire (since you already checked the left in part 2). Any binding will contribute to the issue.

 

*For tests 2 and 3, be sure manual hubs, if equipped, are locked.

[EricCR]

No suspension mods, fully stock facelift R50 with original 16" SE wheels. Tires are 245/65R16 if I'm not mistaken, Cooper AT. No rubbing when turning. The only issue I have is a saggy rear suspension but I have the new shocks and springs at home in a box waiting for me to stop procrastinating.

 

I'll do all those 3 tests and report back. Thanks!