My neighbor has a 2006 jeep grand cherokee she bought new. she says that when driving normal (35mph and there abouts) the car sometimes fishtails, on dry roads. She brought it to the dealer and then a mechanic and both found nothing wrong, they just told her its normal because the car is light in the back. One said to put some bags of sand in the back. I told her they're crazy. Fishtail on a dry road!!??
Any clue what she should do?? Or the cause?? I would guess something with the sway bar but I think that would be very obvious to check. Thanks --again.

Does the fishtailing occur when she is driving straight and just gives more throttle (or lets off), or does it only occur when she is turning?

she says mostly on turns (she mentioned a specific location that it happens a lot,possibly a sharp turn but she doesnt go fast)., sometimes straight and under acceleration. she also says they checked tires and pressure and all were good.

Is there any possibility that the vehicle came from the factory with a limited slip differential in the rear, or that some previous owner installed a limited slip differential or a locker in the rear?

If you are familiar with the corner where she says it happens most frequently, is there anything unusual about that corner? Is it off-camber, or having some sand on the road surface, or water from drainage, or anything like that?

The only experience that I've had that sounds exactle similar to that is because of my rear locker. Shortly after installing the rear locker, I broke a rear half-shaft on one side. So only one wheel was getting power. The other occasion was after I converted to a Warn full floater rear axle (with locker) and had locking hubs on the rear so I could unlock them for flat-towing the Cj7. On one occasion, one of my smarty buddies unlocked one of the rear hubs. Never noticed it on the trail (was in 4WD), but I did as soom as I put it in 2WD back on the pavement.

On both occasions, it would fishtail when the gas was either applied or removed smartly, just going straight. Apply the throttle, it would swerve in one direction; let off the throttle and it would swerve in the other direction.

That's why I asked about the LSD or locker.

She is the original owner so I would have to say the car came with whatever rear it should have. So if I'm understanding this correctly...there's a chance she has limited slip so one wheel gets the power (different than a locked diff where both wheels spin) opposite of positraction. Then what differential is a 2006 grand cherokee supposed to have from the factory?? Is there an ID tag I could crawl under and look at?
But also limited slip dosent normaly make cars fishtail on dry roads(? I never experienced it in other cars). I had a 80 pontiac turbo trans am with posi and that fished in the rain . hmmm...I'm way confused. I think I need to ID her rear end. no pun intended (or maybe..)

What is the engine size? Has it been modified in any way? Engine wise anyway.

My grand has a V8 4.7L and has been slightly modified with the cold air intake, and a larger throttle body. I can with ease get the rear end to do some funny things on dry pavement. Forget driving on snow been there done that, no traction at all just wheel spin.
All this due to squeral problems. <img src="/forums/images/graemlins/smile.gif" alt="" />
just wondering

Defiantley a stock car, no mods. She's not home but the car says grand cherokee laredo. dont know the engine size yet. more info as it comes....
I'm thinking,,if its a full time 4 wheel drive thing , maybe one wheel is getting too much juice, since its all electronic. you know how electronics are <img src="/forums/images/graemlins/scared.gif" alt="" />

Yeah, it has the Quadratec Traction Controls in it. I can tell the engine size by the tail pipe, but that's me.

You know, I had a problem with a speed sensor problem twice with mine. Twice! Same sensor. It would not since what gear I was in ( go figure!). It is on the Trans. It would switch the gears in and out at various times because it was not reading the points. Happened on a trip that lasted about 300 miles and it was ruff. Dropping gears and raising gears to find it's self. The problem was solved with a replacement part $86. It kinda decided to do what it wanted when it wanted, turns or straits, it did not care. The dealer could not find it either. had a personal mech. find it.

I guess I'll mention a speed sensor switch then? I wish I new a competent mechanic here. thanks. any other info is appreciated .

Trex -- Positraction is just a brand name for one of the limited slip differentials put in the rear end of cars. I'm not that familiar with the lineup on Grand Cherokees, but I suspect that, like my T4railblazer, an LSD was an option on the new ones. She may not have particularly ordered it, or even wanted it, but if it was in the particular GC she liked, it would have stayed in there when she bought it.

Most LSD's (except gear-driven ones) require that a friction modifier additive be added to the gear oil in a differential. The gear oil should be replaced every 3 or 4 years, depending on the type of driving. Sometimes, just adding another 4 oz. bottle of friction modifier additive to the existing gear oil will do the trick. Also, several types of gear oil available now come with friction modifier already in it.

There are basically two things that can happen if the gear oil ned some friction modifier additive. (1) The LSD clutches
can slip a lot, which means that the LSD wouldn't work as well, and the rear end would act more like an open differential. (2) The LSD clutches can start intermittently grabbing, causing the LSD to repidly engage or disengage. #2 is morst likely to happen when: (a) the car is in a turn, which means that the wheels are traveling at different rpms, or (b) when power is suddenly applied or removed when going straight. Of course, these symptoms would be exacerbated if the road surface is anything other than clean and dry.

If she has the original sale paperwork from the dealer, it may state whether or not it came with an LSD. If she doesn't, then you may be able to take the VIN number to a Jeep dealer and it may show what type of rear diff it has. There's probably some web site you can go to for that decoding info, but I don't know what it is.