Final drive (differential) seepage on 1987 300TDT (S124) - PeachParts Mercedes-Benz Forum

swogee · #1 07-28-2010, 01:18 PM

I originally posted this on diesel discussion, but it would apply to any 124 chassis Mercedes. I am posting it here in the hopes that someone in this forum will have ideas as well.

The final drive (differential) on my 1987 300TDT (S124) seems to still be leaking after the replacement of many seals and parts. The leak seems to be occurring on the right side output seal.

The final drive has been serviced several times by my local MBZ shop and several solutions have been tried to correct the problem.

1) Three sets of output seals have been tried. The first two were Elring and the last was a genuine MBZ seal set.

2) New flanges were installed on both sides of the differential. (The seepage occurred with both the old and new flanges.)

3) The seals were "set in" at different depths so they would ride on different areas of the flanges to see if that would correct the leaks.

4) The final drive vent was verified as being clear and open.

5) Initially the fill was Redline 75W-90 GL-5 synthetic gear oil and this was switched to regular 80W-90 gear oil. The final drive leaked with both oils. The final drive has been refilled with the Redline 75W-90 GL-5 gear oil.

6) The fill level was correct in all cases. (All work was performed by factory trained ASE technicians familiar with MBZ vehicles.)

The owner/technician is out of ideas on what might be cause the seepage of oil since the solutions above were tried.

I am looking for ideas on what might be causing the oil seepage from around the output flange on the right side.

The only thing I can come up with is:

Crack in case of final drive? There is no obvious cracks, but a magnaflux would have to be done to check for cracks. The only solution would be a new final drive.

Thanks in advance.

-Steve

david s poole · #2 07-28-2010, 01:47 PM

perhaps the mount bushings at rear of diff are worn causing the diff itself to tip to oneside[usually left] when torque is applied thru drive shaft.if you put car up in air with driver,put on emergency brakes,have driver put in drive and use accel.if bushings are worn you will see diff tilt to oneside.

babymog · #3 07-28-2010, 07:05 PM

What's an "(S124)" Steve?

swogee · #4 07-30-2010, 11:04 AM

Thanks for the good ideas. I'll check into the mount bushings on the differential.

As for the question about the "S124", it seems that the proper chassis designation for the 124 series wagon is S124 and not W124. The W seems to refer to the sedan body and the S seems to refer to the estate or wagon. (C is for coupes and R is for roadsters I believe.) The mechanic that I take my 300TDT told me about this a few months ago as I had assumed that "W" was used for all 124 series vehicles.

Here is a link to a thread on benzworld about it.

http://www.benzworld.org/forums/general-mercedes-benz/1390480-does-w-stand-anything.html

Here is a link to an Australian website that mentions it towards the bottom.

http://www.mbspares.com.au/Information/Understandingchassisnumbers.aspx

The chassis series letter "S" of course is totally different than the letter "S" used in the model/class nomenclature that denotes the large "S" class sedans.

Please keep the ideas coming.

Thanks again,

-Steve

swogee · #5 09-30-2010, 01:55 AM

Update:

The technician examined the axles on both sides and noticed that the passenger side axle seemed to have more movement (runout?) during operation which might be causing the seal to leak. The passenger side axle was replaced with another remanufactured unit and both seals on the final drive were replaced.

About a couple hundred miles later, I inspected the final drive and there was oil droplets on the axle bolt flanges. The bottom of the final drive case had some oily residue as well but no drops.

Any ideas on what might be causing the oil seepage would be welcome.

Some pictures can be found in the diesel discussion thread here:

Final drive (differential) seepage on 1987 300TDT (S124)