Hi folks,

I want to change the oil in my differential since my car is 20 years old and since I have no history on the car I can only assume it is the original oil.

I know that if it is a limited slip diff it should have a tag bolted on to the side of the diff., but the absence of evidence is not evidence of absence! My diff does not have a tag. I have 2 clues that make me think I MAY have a limited slip diff. 1) With the car off the ground, if I rotate one rear wheel the opposite wheel turns the same way. 2) My wife was following me in our Volkswagen and said that both wheels were throwing snow when starting off in a recent snow storm. How do I determine for SURE?

I'm aware that MB calls for different lubricants for the different differentials. The 300e Bible says synthetic lubes are not approved. I've always used Mobil 1 75W-90 in my strait diffs. What kind of lubes do you folks use for either type diff?

Thanks as always.

Bob Kopicki
'67 TR-4a
'76 GMC C-15
'85 XJ-6
'87 300e
'97 VW Cabrio

Safely raise both rear wheels off the ground and turn one while observing the other. If both wheels go the same direction it is an LSD, if they turn opposite directions it is an open differential. I am VERY surprised that both wheels turn the same direction on yours. I have never seen a 124 with an LSD. If it is you will need to add the friction modifier when you change the lube. Put only enough of the friction modifier in it to keep it from clicking in a sharp turn.

I am not surprised that Stan or whatever his name is, would say that synthetics are not approved. He used to seem like a very knowledgable guy until he lost his credibility by putting out that Bible book. All it amounts to is a compilation of various facts and diagrams from factory MB material. As far as I'm concerned he lost credibility BIG TIME when he put out that book. Before the book he seemed like the authority and after the book he just seemed like a robot that could read MB material.

I believe that reality is that because synthetic gear lubes were uncommon at the time of the 124 design, MB had not yet taken a position. Since MB had not officially issued anything on the subject, the robot had nothing from MB to refer to, so he printed that non committal statement about synthetic gear lube because he was totally lost with no thinking power of his own.

Make sure that you think about how you will manage to get lube in once it is empty. I have a pump on a five gallon can of lube. You probably can use squeeze bottles. Place a drain pan underneath and REMOVE THE TOP FILL PLUG FIRST! This is so that you know for sure that you can remove it so you will be able to refill it. Then pull the drain plug and drain. I think it is a 14MM socket head, commonly known as an Allen.

Good luck,

You don't have to worry that that diff is limited slip...never available on USA models..

Starting in 1991 a few diesels had ASD as an option in the USA, but not a single gas powered one.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Larry and Doc, thanks for your replies.

Like I said, I have no history on this car. Without a doubt the rear wheels turn in the SAME direction when I have the car off the ground. If the direction of the wheels turning is the litmus test that proves one way or another the presence of a LSD, I would have to say there is a LSD in my car regardless of whether LSD's were or were not supplied as original equipment.

I've never owned a LSD and know very little about how they work or what lubricants they use. Would I be right to assume that putting straight gear oil in a LSD could cause damage to the LSD, but putting the correct LSD lubricants into an open diff would probably cause little damage? I'm just afraid that without KNOWING which diff. I have I could do more bad than good by changing the oil with the wrong lube.

If we assume a LSD is in the car, Larry are you saying I can use regular or synthetic (which I prefer) gear oil and then add a friction modifier. I have no baseline as to how much of this modifier to add. Where do I start? Enough to keep it from clicking? Is there something that is pre-mixed?

Lots of questions, sorry.

Bob

Really bad that you have incorrect info...

Many differentials will allow both wheels to turn...You don't have a LSD in that car.

Any good 80W/90 hypoid will work.

__________________
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

Why do you say that? ASR (and ASD) was available as an option on the W124, and I know my 95 E320 had it. It was probably an option determined by engine size, and 3.0 liters for the Europeans is of gigantic proportions.

Follow up: I think I found one source of the confusion. You probably have ASR, a Limited Slip Differential. It is only the ASD, or locking differential, that has the tag on the outside. Both require the same oil, though. Source: WIS

If the car were mine I would be using regular hypoid gear lube because that is what I have on hand. If I had a hankering to use synthetic, however, I would not hesitate.

The Doc is correct as always, sometimes open diffs will turn both wheels the same direction.

You could leave two strips of rubber with an open diff, not a real test.

I agree that there was no ASR, ASD, nor LSD option on the 124 body in the US in '87. It was standard on the 190E 2.3-16 in '87, and on all 5.6L cars, but not available on the 124 until the '91 4matic and diesel ASD cars.

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Gone to the dark side

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