jonathancl

Edit: Apparently this is normal for awd cars, esp w wide tires and tight turning radii.

2013 GS350 AWD Lux, 78k miles.
Searching a number of things didn't turn up a thread on this, so I may not be using the right words...or I actually have an issue.
There's a TSB for some older LSs for a similar condition.

When making very slow turns with the wheels turned all the way in reverse or forward, the car shudders.
I notice it most backing out of my driveway and in tight parking situations.

Internet seems to refer to this 'torque bind' (Subaru) or 'awd shudder'. I've experienced this in 4WD Jeeps when the farthest outer wheel is covering much more ground than the inner: the differentials are busy, and sometimes you need to use a little extra gas to maintain the same slow speed.

Sometimes I swear the wheels are almost slipping, and on wet surfaces or gravel, I think the outer wheel does occasionally slip a little, feels like it skips.
I have no errors, no warning lights, perfect behavior across the board under every other driving condition.

Is this normal? Am I just being super sensitive? Is there something I should look at more closely?

bclexus

Read about Ackermann Steering Geometry and also about Scrub Radius and Squirm.

When a car with a tight suspension and wide tires makes a small radius turn at a slow speed, one of the front tires can slip, jump or jerk.



You'll find it slips/skips easier when you drive over a surface that has both dry and wet patches - with the wet surface making it slip more, or when turning sharply on a surface where there are painted lines (e.g. parking lot) because the paint eliminates the normally rough surface texture.

jonathancl

So you're saying they all do that, and I'm just being super sensitive?

Because some cars recommend fixes, like replacing fluids in differentials or transfer cases.

bclexus

As stated - it is typical - commonplace ... not for just the GS 350, but many vehicles.

Replacing fluids in the differential or transfer case is preposterous.

AJLex19

I've noticed the same thing in both my pop's '11 GS350 AWD with 42k miles and my '13 GS AWD with 53k miles. Whenever i'm getting out of my driveway, I have to turn the wheel all the way to make the proper "cut." I always feel a slight judder and i'm always moving very slowly. Its seemingly more pronounced when the pavers/concrete in our driveway are wet.

I've also replaced the rear differential fluid but that didn't alleviate the judder.

Knucklebus

This can happen to any vehicle with a suitably short turning radius and a long-ish wheelbase, not just AWD. If you don't turn all the way to lock, it won't happen, correct?

joedaddy1

iTrader: (1)

my AWD does this.. figured it's pretty normal.

drgrant

My 2015 F sport AWD CPO has done this since day one, and it only had 11,500 miles on it when I got it. Basically if you are like 5% away from lock it won't do it... it only happens when I am working tight parking or trying to work a 3 point turn on a street or something. The slower you go the less likely it is to happen.... and also ice, etc, or even just moisture on the surface seems to 'induce" it a lot more...

I think bclexus's post is spot on it describes the issue well. I can see how it would be unsettling if you hadn't experienced it before, but its pretty normal for these cars... the tires are fat, and have a big contact patch... the fact that the car has a pretty wide stance probably aggravates it too. I'd take the tradeoff though any day of the week, for a little "judder" in like .02% of driving conditions encountered any day of the week... the way the wheels on this car are set up is dead sexy, and I think it helps the car handle too.

-Mike