What differential oil weight to use? 85 300SD - Page 4 - PeachParts Mercedes-Benz Forum

ConnClark · #46 12-21-2011, 01:00 PM

Quote:

Originally Posted by SpecialDelivery

need to change my rear diff fluid, so I'm trying to find out if my 1982 300SD has a limited slip rear in it. Other than jacking the car up and turning one wheel...any way to tell? are there model numbers stamped on them or any thing else I can look at?

Does it matter that much on the hypoid additive? can I use oil for a LSD in a non LSD diff? i dont want to put the wrong stuff in it.

No 300SDs made from 78 to 85 had LSDs from the factory. If yours does have one someone put it on the car afterwards.

Cinnamonandgravy · #47 11-21-2015, 11:46 PM

Oh man, if you got this far into the thread... Fun reading, eh?

Anyhow, I just checked my 1983 300d's rear diff fluid 30 min ago, and I'll share my experience.

I don't even jack the car up. It's not comfortable, but as long as the car isn't lowered and you're not particularly thick, you can access the rear diff easily enough. Just crawl under the rear of the car.

To break the filler hex bolt free I just use an old wrench and put the handle inside a steel pipe for extra torque. Takes a little muscle but it's easy enough.

With the bolt out, there's a hole where you can squirt the new fluid into. The hole is fairly high up, and you can just pour the new fluid in; no need for any contraption. Just squeeze the bottle to push the fluid out.

The discussion here seems oddly complicated for such an easy task.

mannys9130 · #48 11-22-2015, 03:10 AM

That WAS a fun read.

I'll tell you what, as a fellow mechanic I can remember one time that I would have been seriously f*cked had I removed the drain plug first. I could not get the full plug out for the life of me and I ended up turning away the service. Had I pulled the drain, I'd either spend the next 3 hours filling through the axle vent or drilling the fill plug out.

tobybul · #49 11-22-2015, 06:55 AM

Although it may sound overly cautious, as Manny said, unbolt the fill plug first to make absolutely sure that after you drain the diff that you can fill it.

leathermang · #50 11-22-2015, 10:07 AM

That was fun and sad at the same time... as Brian did a good job as moderator and then towards the end got more like the example in this thread... I do know that his family had health problems around that time and was a lot of stress on him.

So about specifics in this thread.... I would like to address the ' red locktite' mentioned early in the thread... I put red locktite on all sorts of things... technically it is called ' stud and bearing mount ' meaning that when you put new inserts into a rod end where it will be in contact with the crankshaft... a ' stud' is a double ended bolt which is installed in something like an engine block and is meant to remain there even when the nut at the top.. used to torque down the head... is being removed..
so it needs to require more force to loosen it from the block because it is meant to stay there...this is used to keep that in place.... ...
When people read that description they think ' permanent' very often.... which is not at all the case .... the use of a thread locker is most important as a replacement for a ' lock washer'... a washer cut and bent so it applies pressure to a nut to keep it from backing off.. that is the THEORY....
but the problem is that after it does back off a half a turn THEN NO further resistance to coming off is offered by the split locking washer... locking washers also apply uneven pressure to what is being held which can be detrimental ... even clamp down force is often important.
The effects of Red Locktite are dependent on the size of the bolt or nut... a normal half inch nut or bolt only requires about 5 ft lbs more torque to undo it than a lightly oiled nut and bolt...
but if you use RED locktite on the rear nut on a VW aircooled engine which takes 200 ft lbs of torque to put on... then of course you are going to have major troubles getting that off...
But the advantage , in addition to full thread non backing off protection, is in its function as corrosion protection... as talked about in this thread.... which can add way more than any thread locker to the force needed to remove stuff screwed together...

As to getting that fill plug loose.... in the archives I posted pictures of my ingenious method to apply CONTROLLED large force to that situation without having to jack up the car...

This uses a come-along and the passenger side jacking hole to apply pressure without having to have a long ' cheater bar' ... which often requires more movement distance to be available than is available with the car on the ground...
and more pressure can be applied than is possible with arm or mechanic weight....