I want to change the rear diff. fluid on my C280. I don't know when it was done last. First of all, what is it's purpose? What will be better now that I am changing it? And it is supposed to be changed every 60,000 miles? What kind of fluid should I use? Where can I get it?
Where to start? I know it's on the rear axle, but where? How hard is it? Just drain and fill (opening the fill hole first)? No filter? I uses a 14 mm wrench, correct?

Aghh, sorry for all the questions! I plan on doing this myself, OBVIOUSLY! Thanks everyone!

good diyer job
 

Purpose of the diff. fluid or the differential? Purpose of the fluid is to keep those differential gears lubed.
You more than likely will not see any difference after you replace the fluid. 60k sounds about right. Use a lubricate rated for "gear lube". Based on the type (if it is synthetic it will cover multiple weights) it should go up to 90 weight. I purchase mine local from an advanced type of place. These places will have quite a selection.
You have to raise the rear of the car and make sure it is safe to climb under there (always do this first). Next remove the fill plug (14mm is right) all the way. I would recommend having a 1/2" drive 14mm allen socket to put on a breaker bar to remove them. Put your catch pan underneath the diff. and remove the drain plug. Try to have it hot when you do it. Reinstall the drain plug, fill until it runs out and reinstall the fill plug and you should be good to go.
Jim
'85 300D
'95 E320
'97 CRV

I totally agree.

Be sure to have your car raised in a safe way, because the plugs can be very tight! Change the oil only when hot. I change the oil every 100.000km (60.000 miles).
Clean the area around the plugs first to avoid sand falling in the rear diff.

greetingz,

David,

When I changed mine rear diff lube, I ran the car for about 14 miles into town and back. That got the rear diff warmed up nice, the oil wasn't hot enough to burn when it spilt over my hand.

You want to pull the fill plug first (that's the plug near the top of the diff) because it may be stuck. If stuck and you pulled the drain plug first, how would you ever refill??

Use your ramps. Just back up on the VERY slow and careful, none of these high speed ramp runs into the home gym, OK.

You should have enough room for a one gallon milk jug and funnel. You can drain it directly into the jug, and since you are here in California, you should be able to put the jug out with the recycling bin on trash day. Our waste management company allows two gallons of used oil per recycling day (every other week).

Don't try to filter the gear oil through cheese cloth as you are draining. The oil is too thick and even warmed it will overflow the funnel.

The appropriate specification is GL5. We use Redline Synthetic GL5. I don't remember the exact weight but it is multi-grade with 90 being within the range.

Thanks everyone...
 

Ok, 2 more questions...


1. How much gear lube will I need? Can I tell how much goes into the differential?

2. Where exactly is the drain plug? Or will I for sure see it when I get the car up on ramps? It's just on the bottom of the rear axle?

Thanks again everyone!
Oh and Mike, I will be more careful this time, esp. considering I will be backing out instead of going in, so to speak. :)

a) Put it in till it runs out.
b) You will see the drain plug - should be the closest thing to the ground that screws into the diff.
Jim

Like Jim said "put it in till it runs out". That should be about 2 quarts of lube. You will have a very shallow angle of attack to the fill hole so don't get in a rush. It will be nearly impossible to empty the bottle unless you bought a pump.

Thanks Mike and Enga...

So all I need is a good grade of diff fluid rated 80 or higher...? And then I'm set! Basically, this is a pretty easy job, right?

David,

Jobs don't come much simpler.

I would think you have a limited slip rear diff, especially since Steve stated you need GL5. Stop by the parts house and look at their gear oils, see if you can find what Steve recommends.

Where is the drain plug?
 

I have the car on ramps and I cannot find the drain plug or the fill hole for the life of me! Please someone help soon!!

ANYONE!?
 

>:(

Look on the back side of the diff housing. Near the top, maybe 3/4 of the way there should be a 14mm allen plug, that's the fill plug. The drain plug should look the same and be situated on the bottom flat of the housing.

Let me know if you find them.

Well, Did you locate them?

Not yet, I still haven't put it back up on the ramps. I will soon though! Thanks Mike.