Vibration on tight turns

[Chayro]

New owner of a 98 ML320. When I have to make a tight turn with the wheel turned almost all the way, it feels like the wheels are shaking. This happens at low speeds like when i'm pulling out of a supermarket parking lot or something like that. Everything seems perfect during normal driving or normal turns.

[jfinch]

Mine does the same thing. It is the nature of the beast. They supposedly fixed this in later models with a different transfer case split. The 98 has a 50/50 split front to rear that was changed on the later ones and it supposedly helped this. This is pretty normal for a 4x4. My z71 would groan, vibrate and generally protest greatly when trying to make a tight turn at slow speeds while in 4 wheel drive. If my T-case ever goes out I will replace it with the newer one with the different split until then I am just going to live with it. It is my understanding that it does not hurt anything.

[G-Benz]

I believe they went to a 48/52 and that cured the problem. If brought to attention while under warranty, the dealer would have done the retrofit N/C.

I missed out too. And as jfinch correctly stated, it doesn't hurt anything.

[Jim H]

What you are probably feeling is the tires skidding and scuffing in a sharp turn.

The turn radius of the front outside wheel is significantly larger than the rear inside, so the it has to turn a lot faster than the inside rear.

The rear axle differential was invented to allow left and right wheels to turn at different rates for that same reason. Many years ago, I drove a farm tractor that had a locking rear axle. It's impossible to turn with the rear wheels locked, you just push the front wheels along in a straight line!

If the front and rear wheels are 'locked' by a transfer case, they must turn at the same speed, so something has to 'give' and it's the contact patch of the tires. This effect is more pronounced on long-wheelbase vehicles, such as my Suburban.

Various 4x4 and AWD schemes attemtp to minimize the effect. Limited-slip clutches allow the clutch to slip rather than the tires.

My Suburban also has a slightly 'taller' front ratio, so that the front wheels turn 3-5% faster than the rear even in a straight line. This provides stability by not allowing the rear to try to pass the front, but rather has the front wheels 'pulling' slightly. Great for stability, but not great for tire wear on dry roads.

If you are in any doubt, have a good M-B technician test drive it to get a second opinion, since it is possible that there might be something loose.

Best Regards,
Jim

[G-Benz]

Actually, Jim H, this is a known issue with the early MLs. MB has acknowledged the problem and corrected the transfer case gearing to eliminate it.

Those of us with the 50/50 have learned to live with it. I didn't even know it was a problem until i saw threads about this...

[Chayro]

Thank you so much. My mechanic checked the car out before I bought it, but I didn't notice that little vibration at that time. Glad to hear it's normal.