300SDL axle pinon seal replacement
 

The back axle pinion seal is leaking. It is not that serious but it is very messy back there. I have never done anything on a back axle and I did a search for info here.

It seems that I need a special socket as it is not a conventional nut. Is it true? Is it within the realm of a normal DIY guy? How much I would expect to pay if I take it to a mechanic?

The seal is not that expensive. The tools is about $60 and it may be more worthwhile to pay a bit more to have an indy takes care of it.

Thanks.

I would ask if someone would send you the PDF on that.

I looked in the 124 manual. If it is similar after you remove the Flex Disc they wanted you to use a tool to read the Rotating (driving) Torque on the Differential (but in that section the did not say why you needed that).

Ounce you get the nut off there was a puller to pull off the Yoke that the Flex Disc attach to.
Pry out the seal and install it with the special installer; aka seal driver.
After that it said assemble in revers of assembly. It did not give an torque for or special instructions to tighten the nut or say what that Drive Torque reading was for.. However, I am guessing that is in another section.

I am also guessing that you tighten the retaining nut down until you get the same Rotating/Driving Torque.

I checked m 123 CD Manual and it is about the same. The Rotating/Driving torque is used when you tighten the Retaing nut.
You might be able to measure the differential driving torque with a Beam type Torque Wrench in inch pounds.

Normally a pinion seal is a sign that the pinion bearings need resetting/replacing.

A diff rebuild will be expensive. If there is excess backlash or any noise, best just replace the diff with a good second hand one.

I have done pinion seals on non Mercedes. The tightening torque on the center nut is normally around 200 ftlbs but you need to find out the correct value, it does vary a lot.

The Haynes manual just says its too difficult.

911's suggestions are good.
It is likely that the drive torque will be a tiny bit greater once you put the new seal in and torque it up.
Hopefully some one will have the pdf for us all.

at the dealer, we would use an air gun to take the nut off; mark the nut first so that when you put it back on you can tighten it to the same place it was when you took it off. that way the torque will be very close to the same. this has been done to thousands of diffs with no problems.
to get the flange off the diff, use a brass hammer, tapping each ear around so that you don't get it cocked from hitting just one side. do not use a steel hammer or you will deform the flange. sometimes they slide right off, sometimes you gotta hit em a bunch of times. sometimes you will need a puller to get it off. i use an old bearing race thats just a bit larger od than the seal as a driver to get the seal flush with the diff when installing it. be careful not to cock the seal or it can be ruined. you want to drive it in very straight. put a little grease or oil on the lip of the seal so the flange don't damage it when you put it back in.

Thanks for the info.

I am thinking of replacing it with an used one from a JY. There is a lot of JY here ( close to Mexico ). I think the leak can wait as long as I keep an eye on the oil level. I drained it just now and not much oil come out. I think it is less than 1.0L. It should take about 1.5L, shouldn't it?

If I change the diff from the JY, would any W126 chassis car fit, SE, SEL? How about the year?

How to determine the friction preload
 

http://www.peachparts.com/shopforum/tech-help/233540-pinion-seal-replacement-how-determine-friction-load.html

Charlie

I think Brian Carlton has played with diff changing a bit, you may wish to ask him or whunter about what fits what.

If you use the Torque Wrench the wrench has to be one with a dial or a Beam type Torque Wrench; you cannot use a click tpe torque wrench.

If you use the method where you mark were the retaining Nut is (index it); it is also a good idea to measure or count the exposed threads (both done before you loosen the Retaining nut).

The second part of diesel911s description makes the job easily and safley doable at home. An alternative to getting on the right thread when indexing might be to measure the amount the nut is on with a decent depth type digital caliper. Or modify the one you have temporarily. Before you loosen it. you still have to put an index mark on the nut and use that of course as well.

How much an indy or stealership would charge?
 

I am overwhelmed with projects; cars, house; work etc that this can either wait or have it done by an indy. I can pull one from JY when they have 1/2 price sale but it will be a while.

Any idea how much an indy or stealership would charge for such a specific job?

Thanks

Labor rates vary too much from area to area. I would simply call them on the phone and ask what the loabor charge would be. That way you are not pressured into having the job done by them.
You also may need to make an appointment to have the job done.

Stuck - cannot get the drive shaft out of the way, HELP
 

Attempted to do the seal myself. I marked the location of the disk relative to the flange and removed the 6 bolts that hold the flex disk. The flex disk is loose, the drive shaft is separated from the flange and can be rotated freely if I put the tranny into neutral. The problem is that there seems to be a little shaft inside the flange that goes into the drive shaft :confused:. There is no clearance to slide the drive shaft back to clear it. As a result, I cannot move the drive shaft out of the way to get to the flange nut. The flex disk will not come out either.

What do I need to do next?

I think you could put a Floor Jack under the Differential; Remove the Differential Mount and I believe you could move the Differential down and backwards; being carful not to pinch your Axle Boots.

I have read the forum here that I can take the heat shield out and collapse the drive shaft? Is it doable?

get a big pry bar and pry the driveshaft away from the diff. the pinion has a projection on it that goes into a hole in the drive shaft. it seems brutal, but you must pry it back to get the flex disc off and to get at the nut.