My rear wheels when jacked up on my 560sl 1988 do not turn the same direction when turned by hand , or when the car is in gear and on jack stands.
Is this the way it works on Mb cars?
This tells me the posi is shot.
Are the posi clutches worn out ? Can I shim thim up to load the posi ?
Does anyone sell these clutches besides the mb dealer?
If I try to spin the tires one wheel only spins
Should both wheels spin like all other cars I owned
The rear has the tag for special lube
I did change the lube when I bought it 5 months ago and put posi lube in it
Any help wound be appreciated

560's have "limited-slip" differentials. Many times the wheels won't turn the same direction on a lift! BUT the question is, does the car leave 2 "black" tire strips on heavy accel?

I haved replaced many clutches on the 190E 16V differentials, but only a few on the larger differential in the 560's & 6.9's.
DOUBT if anyone but dealer can get the clutches. DID you use "factory" OE fluid? MB number 129-353-11-62 is the number for the clutches (8 required).

The clutches have a sintered brass material that requires MB special fluid.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

no I have used aftermarket lube.
The problem if its is a problem was before lube change .
I seen guys not use posi lube and get chattering from it but I never had a chatter problem before or after lube change
No filings in the old lube I took out
Are there springs in the center of the spider gears to load the posi ?
I will do some burnouts later today and try it
Then I will try the MB snake oil as you said.

It sounds like you have an open differential.

Jack up one rear wheel and DOUBLE CHOCK the opposite front wheel. Release the parking brake and place the transmission in neutral.

Use a torque wrench on the lug nut with the lever on a radial line and see how much torque it takes to break away. A serviceable limited slip should require at least 40 lb-ft.

If you can turn it by hand, it's probably an open diff.

Clutch and cone type limited slips diffs require a "friction modifier" additive to prevent clutch chatter. GM and Ford dealers sell this additive in four ounce bottles for addition to conventional SAE 80W-90 GL-5 gear oil.

Duke

Thanks
I will check it out tonight
Very informative
If it is bad which I think now it is because when I originally checked it out
I had it in neutral and I held one wheel and move the other the opposite way
I will check it your way. It will give me a correct torque and how bad it really is.
If its bad do I need all new clutches only or is there other cluch parts to the unit.
Thanks again for the help
you guys are good

If it feels like an open diff - virtually no resistance to one wheel turning when the other is fixed in posit'on - then I would suspect it is an open diff. I believe that all 560 SELs got a limited slip diff as standard equipment on US models. You said your car is a '98 560 SL. Do you mean '88?

If it is an OE type limited slip diff, but the clutches are worn, I don't think any harm will be done, but you won't have the limited slip feature, which may only be an issue in marginal traction conditions like snow.

Limited slip diffs should have periodic fluid changes - say in the range of every 30-60K miles. As the clutches wear, particles contaminate the fluid and form a sludge at the bottom of the diff housing. Also, they probably don't add to bearing and gear longevity!

Duke

Yes it is a 1988
I guess its hard to think back to 88
I will rip it appart this winter change seals and clutches
Do the half shafts unbolt from the center carrier ?
So you don't have to take the wheel ends off with brakes.
It's hard to believe with 77,000 miles the posi is shot.

Can't help you on the details of how to remove the diff on a 560SL.

I have some experience with Corvette Positraction diffs. It's not unusual for the clutches to be well worn at 75K miles. and as the clutches wear the differential gear backlash increases and the diff can start to clunk.

On C2-C3 Corvettes the best solution is usually to replace the entire Positraction case assembly that is still avaliable from Eaton, and a less expensive cone type limited slip case is available from Auburn Gear. Setting up the case is tricky and can be time consuming with multiple build-ups/teardowns because the shims between the outboard clutch and case must be juggled to get both backlash and side yoke end play in spec, and the cases themselves tend to crack at the loading window, so a whole new case is the best bet.

You just check that the differential gear backlash is in spec then install the side yokes for an end play check. If both are okay the case can go into the carrier, set up the side shims for correct ring and pinion backlash and bearing preload, install the side yokes, and the final side yoke end play should check out okay.

Duke

An open differential wasn't offerred for the USA version 560's!
Most MB limited slip differentials will only lock up durning HARD acceleration, up to a 40-50% lock-up.

NO springs! only sintered brass & steel clutch discs, that is why you need special lube.

Does the car leave 2 black strips on pavement?

The clutches can be replaced w/o removing the differential. ONLY diff carrier removal is needed.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Here it is boys
I just got time to check it out
I jacked it up and put it in neutral and locked the one wheel
spun the other
the wheel turned very easy
felt like I had a bad posi
Duke I am like you had many corvettes raced them for years
ripped many posi's apart.

But MB Doc 's test was next on the list
Being he worked on benzs for years I would try his test
I just backed it out of trhe garage and layed down two black strips in the driveway.
My wife said I need the help, not the car
So boys whats the verdict
I think it's ok
What do you boys think

I think the best test is to place one wheel on a low traction surface and the other on a high traction surface - like dirt/asphalt, but ice/dry pavement would be best, then give it the boot. Be aware that normal street type limited slips can go into one wheel spin if the torque differential overcomes the clutch torque capacity, so don't get carried away.

Limited slip differentials are rated at "percent limited slip" which is the torque differential allowed before the diff begins to lock up. Street oriented verisons are usually no more than 30 percent, or they can be jerky/chatter in normal driving.

Duke

An open diff would not allow for 2 black stripes on pavement so the limited slip still works, how much & when is the question? The clutches can be replaced in about 4-5 hrs w/o any MB special tools & back-lash would be the same, so no need to set-up.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks for the help Doc
Would I just remove the back carrier cover , pull the axles, pull the posi and replace the clutches leave the shims for back lash as they are
The cd I got from MB does not have anything about the posi
I am also going to change fluid
Is the posi fluid an adittive or is the stuff right in the fluid from MB
The reason I buy from the internet is the MB dearship is a 30minute ride to get to
Are there any MB parts that do UPS.
It's easier to order by mail