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Pelican Technical Article:

Differential Oil Change

Time:

1 hour1 hr

Tab:

$40

Talent:

**

Tools:

14mm internal Hex bit, siphon pump, shop rags, drain tray

Applicable Models:

Mercedes-Benz W210 (1996-03)

Parts Required:

New differential oil

Hot Tip:

Wear your worst clothes while doing this job.

Performance Gain:

A quieter, smoother and cooler running final drive.

Complementary Modification:

Replace differential mounting bushings.

A differential is just like any other mechanism with moving parts. It generates heat and friction while in operation. Just like in an engine or transmission, regular oil changes help to keep the bearings and gears inside well lubricated and clean. Over time, the differential wears just like any other component. However, it has no internal filter to capture small particles of metal as the gears wear. Also, the differential uses oil that is much thicker than engine oil. Usually, differential oil is good for up to 80,000 miles without changing. However it is commonly overlooked in the wide spectrum of vehicle maintenance. Failure to change the fluid at regular intervals can eventually cause the bearings in the differential to fail. In this article I will go over the simple steps to change the oil yourself and avoid a costly trip to your mechanic for something you can do in under an hour in your driveway. For this job, we are using Redline 75/90W Synthetic High-Performance Gear Oil. You'll need 1.5 quarts to fill the differential.

First, drive the car around the block a few times to get the oil inside the differential warmed up. The fluid will flow out of the differential easier when it is warm. Now jack up the car and secure it on jack stands at the factory lifting points. You'll want the car to be as level as possible to ensure that the fluid level is accurate when you fill the differential.

Now crawl under the car and look at the differential. On each side of the differential towards the bottom, you will see two 14mm internal Allen head plugs. These are the drain and filler plugs for the oil. The drain plug sits on the right side of the car near the bottom of the differential. The fill plug sits higher up on the opposite side.

Put a drain pan of at least 2 quarts capacity under the plugs and first open the top plug to relieve any possible vacuum inside the differential and help the oil drain out. Now loosen the lower plug and thread it out by hand. Keep in mind that the old oil will start to flow out as soon as you remove the plug, so make sure the drain pan is directly below. Also, gear oil is some of the worst smelling stuff on earth. If you get any on your clothes, you will never get the smell off again, so be sure to wear your worst work clothes.

Once the fluid is completely drained, you should visually check for any shavings/metal flakes in the fluid. This is typically an indicator of wear inside the differential.

Let the old fluid drain out of the car completely. Just watch it, it will go from a full stream to a small trickle then it will stop flowing. Once it has stopped, clean the drain plug threads and apply a small amount of non-permanent threadlocker. Now thread the drain plug back in and torque it to 55 Nm (41ft/lbs.). Now, get the new fluid and pump the new fluid into the filler hole at the top using a siphon. When the fluid begins to flow out of the top hole, it is full. Now clean the filler plug, put a dab of threadlocker on the threads and thread it back into the differential. Torque the plug to 55 Nm (41ft/lbs). Be sure to wipe up any fluid that may have spilled on the exhaust or on the outside of the differential itself.

The drain plug is located on the right side of the differential toward the rear (green arrow).
Figure 1

The drain plug is located on the right side of the differential toward the rear (green arrow).

The fill plug is located higher up on the differential case on the opposite side (green arrow).
Figure 2

The fill plug is located higher up on the differential case on the opposite side (green arrow).

Remove the fill plug first to relieve any vacuum inside the differential.
Figure 3

Remove the fill plug first to relieve any vacuum inside the differential. You'll need to use a 14mm hex bit with an extension as shown here to clear the exhaust.

Next, loosen and remove the drain plug on the opposite side of the differential.
Figure 4

Next, loosen and remove the drain plug on the opposite side of the differential. Be sure to have a drain pan underneath to collect all the old fluid.

Let all the old fluid drain out of the differential.
Figure 5

Let all the old fluid drain out of the differential. This may take some time, just watch it. When the fluid stops draining, clean and apply some threadlocker to the plug and torque it to 55 NM (41ft/lbs.).

Now, get the new fluid and pump the new fluid into the filler hole at the top using a siphon.
Figure 6

Now, get the new fluid and pump the new fluid into the filler hole at the top using a siphon. When the fluid begins to flow out of the top hole, it is full. Now apply threadlocker to the filler plug, install and torque it to 55 NM (41ft/lbs.).

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Comments and Suggestions:
daleM Comments: Follow up to: Comments: 1991 190e last night my son driving over train tracks heard loud clunk, bang in rear diff. May 28, 2016

Got under the car today, e-brake ON. Transmission in Neutral. All wheels blocked and on the ground. Reached under the car and spun the drive shaft by hand. Either direction. Spins freely both ways. The pinion input is spinning. Something must have broke in the diff?
Any thoughts? Or experience with this. Just had the flex discs and centre bearing replaced 6months ago
Thanks Nick.
June 15, 2016
  Followup from the Pelican Staff: If spinning free without grinding, the connection may have failed. Usually when a diff fails there is noise, resistance when turning or grinding. Pull some fluid out of the diff to check for metal.- Nick at Pelican Parts  
abuze Comments: what are the specification for the socket to remove the 6 bolts off the half shaft plz 10mm i believe.
June 12, 2016
  Followup from the Pelican Staff: I think they are 8mm Allen. - Nick at Pelican Parts  
daleM Comments: 1991 190e last night my son driving over train tracks heard loud clunk, bang in rear diff.
Tranny in drive or reverse car doesn't move.
Jacked up right rear wheel off ground. Put trans in neutral, motor off, spin right rear wheel by hand, Drive shaft does not turn. Wheel turns freely/smoothly.
Reach under car and turn drive shaft by hand, motor off, Trans in N, jacked up wheel does not turn.
What broke? No grinding or noise from rear diff while turning by hand.
May 28, 2016
  Followup from the Pelican Staff: Check the flex-disc at the drive shaft. I doubt it is internal to the diff. - Nick at Pelican Parts  
Greg Larsen Comments: I have a 300e that was low on differential oil and caused a vibration when taking off. It's full now and doing better, but it still has a slight vibration when taking off. Why is it doing this and what do I need to replace? Thanks.
April 28, 2016
  Followup from the Pelican Staff: You could have a faulty diff or a vibration in the driveshaft. First inspect the driveshaft for binding or worn joints. - Nick at Pelican Parts  
Loren Comments: I'm planning on replacing the differential oil in my 96 E320, so I naturally read through this article. My question is regarding the replacement oil. I see other oils out there that are synthetics like Mobil 1 75/90 or Motul 300, 75/90 gear box oil. Is there a better oil than the stock replacement oil? What do you recommend?
I really appreciate your information and parts selection.
Loren Jennings
March 13, 2016
  Followup from the Pelican Staff: I always stick to factory fluid. You can however sometimes improve on it. As long as the fluid is approved by MB. Give our parts specialists a call at 1-888-280-7799. They can help you find the right fluid.- Nick at Pelican Parts  
George Comments: Great pix, easy to follow! Thanks a million, Wayne! The only thing I'd add is, this is a difficult task if you can't get the car off the ground. There just isn't enough space to work. Elevate the car with whatever you have, and be safe.
January 1, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Mike Comments: I have readin service book to replace the rear axel differential oil if it is 'limited slip differential' at 2000 miles!
I have two question about this:
1- Does an E350 4Matic Benz come with a limited slip differential in the rear?
2- How much of this oil do I need, I couldn't find capacity anywhere,
my guess was about a liter of 'FE 75W-85'? Don't want to buy too much of this expensive oil.

Thank You
January 1, 2016
  Followup from the Pelican Staff: Capacity should be under 2 quarts. Maybe even 1. To be sure, Give our parts specialists a call at 1-310-626-8765

LSD checking
List and support the rear of the vehicle. Spin a rear wheel, if the opposite side spins in the same direction, it is an LSD. - Nick at Pelican Parts
 
Kevin Comments: Hi Pelican,

I have a 1995 C220. Just wondering what type of Gear Oil I should use - 75W90 or 80W90?

Thanks!
November 13, 2015
  Followup from the Pelican Staff: Depends on your diff. YOu will need to confirm hat you have, for example: BB00.40-P-0235-00A Hypoid Gear Oils (SAE 90, 85W-90)

MB 235.0 hypoid gear oil A 000 989 28 03 - Nick at Pelican Parts
 
engapol Comments: Is it ok to not use threadlocker on the plugs? They were VERY hard to get off in the 1st place and I don't want to strip them if I have to access the diff again.
October 13, 2015
  Followup from the Pelican Staff: If torqued properly, they should come off OK next time. - Nick at Pelican Parts  
Vito Comments: Is it a big deal if I use 80/90W synthetic gear oil instead of 75/90W? What's the difference between them? Thank you
August 10, 2015
  Followup from the Pelican Staff: The weight. What vehicle do you have? - Nick at Pelican Parts  
Ray Comments: the drain plug 14 mm was stripped by the previous owner and I can't get the plug out. Should I use a cold chisel and beat it out or is there a more civilized say? Also I looked for the "Vent bolt" on the top of the chunk and didn't see one, is there one? The car is a 77 Mercedes 450 SLC. Your expert advice is welcome. Where can I purchase a "Plug" once it comes out?
March 15, 2015
  Followup from the Pelican Staff: we have the plug. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.


As far as getting it out, try using a Torx bit of similar size and hammering it in. Or a 9/16 Allen bit an hammering it in. Just don't hammer too hard, you don't want to damage the oil pan. - Nick at Pelican Parts
 
Raines Dave Comments: Nice and informative article! What is the procedure for getting and replacing differential for Benz C240 2001 model?
February 13, 2015
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Mike Comments: I think your differential will start whining as the bearings wear out, and the noise will increase as the condition worsens, so a minor and intermittant noise is not a sign of imminent sp? failure. This is a useful tech article, but it omits the most important reason to remove the upper plug first, which is to be certain that you will be able to re-fill the differential case after you drain the old fluid. The last time I did a differential fluid change, I used an L-style hex "allen wrench" in the plug, and used a box wrench to turn it.
June 19, 2014
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
 
gabz Comments: I have a 1996 e320 , just went in to do an oil change at valvoline. Had them check my differential fluid , they said it was low and was clumpy. What viscosity do I use for the differential fluid??
March 24, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right fluid.
- Nick at Pelican Parts
 
Daniel Comments: Your directions are very detailed an sounds easy but I would like to know what the "Replace differential mounting bushings" looks like and how do I even find it from your parts list? Because, I couldn't find it maybe because I don't know what it looks like? by-the-way. I have 2002 E320 4matic. Thank you.
February 19, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
We don't currently have a tech article for that procedure. If we get the chance to perform the repair we will be sure to document the process. - Nick at Pelican Parts
 
Brie Comments: I was told by jiffy lube 8-31-13 when having an oil change that I neeeded rear differential. It was my 1st time ever hearing those words in reference to my vehicle a 1990 300E 4door sedan mercedes. He said fluid was little to none so he replaced the fluid but advised rear differential asap. I'm only now able to afford to have rear brakes done & have rarely been driving it. The noise still continued even after oil was replaced the noise only occurs when I 1st start up the car for the day & put it in drive & barely push on the gas it has a rumbling noise for about 2 seconds then stops. I'm having rear brakes pads replaced tomorrow what should I expect from the mechanic when I explain the differential situation to him? Please advise!
December 2, 2013
  Followup from the Pelican Staff: If the noise is truly from the differential (and not the rear brakes or wheel bearings) then all you can do is either replace the differential now or wait until it seizes. Depending on amount and intensity of use, the diff could go years and just make more and more noise until it seizes. - Nick at Pelican Parts  
Home mechanic Comments: Outstanding information! I have a 1995 Merc. SL320 and am getting a rumbling sound and vibration. I looked under the car and see a small leak on the rear diff case. Does the case need fluid or something worse?
October 9, 2013
  Followup from the Pelican Staff: I hope the vibration is from a worn center bearing in the middle of the driveshaft. Drain and refill your rear diff with gear oil and see if the noise goes away. If not and the fluid level was low you may have already damaged the diff by running it low on oil. A professional mechanic would lift the car till the wheel were off the ground and use a stethiscope or an "engine ear", start the car put it in drive and accelerate a little and listen for the rumbling. An older mechanic would do the same thing but hold a long screwdriver against the diff or spindle (NOT A ROTATING PART)and put his ear against THE OTHER END OF THE SCREWDRIVER and reposition the screwdriver until he isolated the noise. Running the car on a lift requires some skill in setting up the car so vibration will not affect it. - Kerry at Pelican Parts  
BEN Comments: hi! I have 1997 m.benz e-320; the trans require service/?
thx
August 1, 2013
  Followup from the Pelican Staff: Is this a question or statement?
Please use full words and a complete sentence.
Thank you
- whunter
 
David E Klasse Comments: does this same procedure more or less apply to the W211 E320?
June 20, 2013
  Followup from the Pelican Staff: If you have a dipstick tube, it may be close enough to work.
-whunter-
 
Eric Comments: Hello! Can you let me know if a 1997 Mercedes E420 W210 comes with a sealed transmission? Meaning no need to change transmission fluid ever on this model. I checked with my dealer and every time that is what they tell me.
June 6, 2013
  Followup from the Pelican Staff: Mercedes Benz reversed course and now recommends service on all transmissions, even the units marketed as forever filled.
Go to a different MB dealer and have it serviced.
-whunter
 
steve Comments: would low differential oil cause a humming noise
May 3, 2013
  Followup from the Pelican Staff: Usually low differential oil will cause a whine noise.
Humming, rumble or growling is usually a bearing noise.
whunter@pelicanparts.com
 

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