4matic troubleshooting- no codes
 

Recently acquired 91 300TE 4matic with 91K miles. Rebuilt MB transfer case @ 80K miles. When making U-turns or small radius turns, it feels like front or rear is 'binding' up... like right and left side are not turning independently as they should. Also, when accelerating or just before coming to a stop under braking there is a series of subtle jerks coming from drivetrain.
No warning lites are illuminated on the dash and NO codes were pulled.
Also, when the lever is put in 'test' mode, car drives smoothly. All the issues go away. All fluids in trans, transfer case, and hydraulic were recently replaced and are at proper levels. No leaks.
Is this a sensor problem or something mechanical in the differentials?

Hmmm
 

The last time I saw an issue like this, it came out to be the previous owner had the car towed on a hook type truck. :(
The repair cost was several thousands of US dollars, at the MB dealer. :(

All four tires must be the same height, tire pressure, size. Any lights on the dash ,ABS,ASD warning,ASD function. I work on one, years ago, it had a bad steering angle sensor. The 4matics have a very complicated system , I guess you know that already.

Good luck.

Tire size "already stated" is VERY critical...but since the lamp is on & no codes that means a hydraulic problem...You need so start by having the system bled.

ALSO have the fluid level checked in the transfer case...if it is high then CHANGE that fluid(ATF.. separate fill) & have the hydraulic system to the transfer case bled..

M.B. Doc-
The hydraulic fluid was just changed and is at proper levels. I also had the fluid in the transfer case also replaced. Hydraulic fluid shows proper level in the bottle.
Could the mechanic have messed up with the transfer case fluid.
P.S. I mentioned that when I move the lever in to 'TEST MODE', the car drives like a dream. I was under the impression that that rules out a hydraulic problem..... but again, I am just parrotting what I've read in many threads on this site.
Any further thoughts? Thanks

With scanner do you get code 1 which means NO faults OR do you get no codes as you first stated...

IF no code appears then the problem is Hydraulic...again bleeding the transfer case & activating the solenoid for the differential & then bleeding it IS the correct starting point...of course the engine MUST be running to bleed that system & there are bleeder at both places.

Ask your tech if the transfer case was too full...that is the most common leakage point for that system...Fluid should NOT come out of the fill plug..but be level with that plug.

M.B.Doc-
I am going to have codes checked again.

When you describe the method to bleed the TC, are you implying that the mechanic may have drained the TC incorrectly before and either allowed air in or somehow botched the refill of trans. fluid into the TC? Is there a 'wrong' way to drain/refill the TC?
As to excessive amount of fluid in TC, there has been no leakage of hydraulic fluid into the TC. Hydraulic fluid level has remained level in bottle prior to and since it was replaced.

The TC has its own fill of ATF & there is a hydraulic clutch assembly that applies(solenoid application) EVERY time that you drive up to 12 mph.

UNLESS they disconnected that hydraulic line (no reason to) the technician Could NOT have caused that problem.

Look & measure the tire size...IF there is even a 1/4" difference between the front & rear you will keep the system engaged when IT shouldn't be..

The rear tires MUST have exactly the same circumference & can't be shorter than the front tires at all or the system will activate & lock the rear differential.

tire size
 

The car has brand new OE spec 195/65 15 ContiTourings all around.

Did you measure the circumference of all 4 tires? even new tires can have different heights...did the problem start with tire replacement?????

could be steering angle sensor.i had some vibration from my front diff awhile back.this was solved by a change to synthetic diff oil.recommend synthetic for the xfer case as well.only 1 litre in there so you want the best heat durability:)

I know it sounds too easy but I have had one similar where the diagnosis was killing me. 4-Matic light, no codes...Turns out the brake light switch was open circuit and this was keeping the control unit in fits. Microprocessors understand connected to ground (binary 0) and connected to positive (binary 1) So open circuit doesn't fit into the program. I eventualyy found this by grabbing at straws after a complete hydraulic test. Now every time I have a difficult 4-matic I try a brake light switch just for the hell of it, though I have only had it be the fix for that one car. May just be worth a try in your situation, after all it is one of the cheapest components of the system:rolleyes:

4matic help needed!!
 

One thing you might consider...when the car is first starting up the 4Matic is always automatically engaged. this means that if you are just starting up and turning a tight corner, as you probably will be doing in a "U" turn, the 4Matic has all wheels engaged. Once you are over the 12mph or so speed, and there is no road condition requiring it, the 4Matic system shuts down. As you state, when the system is in "test mode", which is essentially turned off, you do not feel this condition.

SRHarvey,

No 4Matic
 

Sorry I posted here by mistake

Thanks

Roger