Mercedes Rear Differential Fluid Change

One of the most overlooked fluid items on any car is the rear diff fluid.  This is not permanent fluid!  It is designed to be changed periodically.  I normally like to change the fluid to Amsoil synthetic 75w-90 when I get a car in the shop.  This is not a hard job to do, you just need to be careful and plan ahead.

So lets once again get our pictorial mule, the ole 79, in the shop and get the rear end lubed up...

Note: while this may not be the same Mercedes model as yours, the procedures are relatively the same.

Safety and security tips:

Please remember to recycle all your used fluids at an appropriate recycling center.  Be mindful to not spill or splash fluids on yourself, others or the ground.  Also as a safety tip please remember anytime you are working on, around or under your car, to wear safety glasses and secure the car with wheel stops and approved jack stands!

Car is ready to go up the ramps.....

Safety first because safety lasts.  Get the car on a good pair of ramps or jack stands.  Do not use a floor jack or the jack to repair your spare tire.

Don't forget to chock the front wheels so the car will not roll forward.

The tools needed are a 14mm Allen wrench, drain pan, gear oil.

Here is the rear diff.  Notice the two plugs.  Upper one is the fill, lower one is the drain.

Always remove the fill plug first.  Why you may ask?  Because I have heard of many stories when the fill plug was stripped of frozen, AFTER the fluid was removed.  Then how will you get the fluid in the diff?  So be on the cautious side, remove the fill plug first to be sure it will remove.  Clean around the plug before removing it.

A very substantial fill plug is in the old diff.

Next remove the drain plug and allow the contents to drain into your catch pan.

This is how I get the fluid into the diff.  I have tried a every way know to man and it a mess.  I like this pump and hose assembly, works great with no mess.

The pump in action.  Notice there is no mess!

The tube just fits into the fill hole.  Fill to just the point where the fluid starts to dribble out the hole.  The car is on a slight incline toward the front, so you will get a few more ounces in the diff than you would if the car was level.  If your really anal then put the front of the car on jack stands and get it level.  The few extra ounces will not hurt anything.

Button up the fill plug and your done!

Now go enjoy the new lube in your rear.

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