Differential fluid change DIY?

I was aware of this Rule, but it certainly bears reminding everyone who may read this thread. Without an LSD and thus no need for a friction modifier, choice of lubricant certainly opens up. I will lean toward Mobil 1 simply because the Base Exchange has a full selection, though I've had good luck with Royal Purple and Amsoil in the past. Thanx!
advance oil has the hand pump that fits on the oil bottles. a must have as you cant tip the bottle into the fill hole. about 8$
At the time, I really didn't give any thought to the differential fluid. Threads covering changing the differential fluid and how often you should change the fluid are sparse in this forum.
Page 388 of the owner's manual in the "Fluids" section references a "Rear Axle" fluid. Is it safe to assume this is the differential fluid? It states that the replacement for the C55 is 1.5 US qt. of Hypoid gear oil SAE 85 w 90.
Also, how often is this fluid supposed to be changed? I am going to be kicking myself if its every 40,000 miles as I would have just had my indie do the change while it was in the shop for the transmission flush.
At the time, I really didn't give any thought to the differential fluid. Threads covering changing the differential fluid and how often you should change the fluid are sparse in this forum.
Page 388 of the owner's manual in the "Fluids" section references a "Rear Axle" fluid. Is it safe to assume this is the differential fluid? It states that the replacement for the C55 is 1.5 US qt. of Hypoid gear oil SAE 85 w 90.
Also, how often is this fluid supposed to be changed? I am going to be kicking myself if its every 40,000 miles as I would have just had my indie do the change while it was in the shop for the transmission flush.
A lot of modern cars have a "lifetime" fluid that theoretically does not need to be replaced. I don't trust that BS and would do it every 35-40k miles depending on driving style (My old M3 manual recommended it at 50k and that had an LSD).
Super easy to do.
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A lot of modern cars have a "lifetime" fluid that theoretically does not need to be replaced. I don't trust that BS and would do it every 35-40k miles depending on driving style (My old M3 manual recommended it at 50k and that had an LSD).
Super easy to do.

Just remember to remove the fill plug first in case you can't get it off. It'll be a bit late to find that out after you've removed the drain plug.
- Jack up car in back and place on jackstands. I use a set of Rhino ramps with my Tacoma and it saves the jacking. http://www.amazon.com/Blitz-Rhino-Ra...8387725&sr=8-1
- Find the "pumpkin" in the rear axle. It's where the diff and drain/fill bolts are.
- If there is a separate dedicated fill bolt, remove that.
- Remove diff drain bolt. Usually takes just a 1/2 inch or 3/8 inch drive. From my Ranger and Tacoma, they don't need any sockets, just the half inch drive. Could be different for the Merc.
- Suck out the old fluid. I use a Mityvac fluid exvacator, but I have heard cheaper pumps available at Autozone also work successfully.
http://www.amazon.com/Mityvac-7400-L...sr=8-1-catcorr - Re-fill diff with recommended fluid. I have seen both ways - re-fill using same bolt or re-fill using a separate, dedicated bolt at a higher point on the pumpkin. I have never had to use a pump to re-fill, the diff fluid bottle comes with a funnel that usually suffices.
- Close up, drive a few minutes. If you are really cautious, re-jack car and check level. But as long as you got recommended or close to recommended amount of fluid back in there, you should be fine.
Last edited by xxaarraa; Feb 22, 2011 at 11:41 AM.
- Jack up car in back and place on jackstands. I use a set of Rhino ramps with my Tacoma and it saves the jacking. http://www.amazon.com/Blitz-Rhino-Ra...8387725&sr=8-1
- Find the "pumpkin" in the rear axle. It's where the diff and drain/fill bolts are.
- If there is a separate dedicated fill bolt, remove that.
- Remove diff drain bolt. Usually takes just a 1/2 inch or 3/8 inch drive. From my Ranger and Tacoma, they don't need any sockets, just the half inch drive. Could be different for the Merc.
- Suck out the old fluid. I use a Mityvac fluid exvacator, but I have heard cheaper pumps available at Autozone also work successfully.
http://www.amazon.com/Mityvac-7400-L...sr=8-1-catcorr - Re-fill diff with recommended fluid. I have seen both ways - re-fill using same bolt or re-fill using a separate, dedicated bolt at a higher point on the pumpkin. I have never had to use a pump to re-fill, the diff fluid bottle comes with a funnel that usually suffices.
- Close up, drive a few minutes. If you are really cautious, re-jack car and check level. But as long as you got recommended or close to recommended amount of fluid back in there, you should be fine.
Mobil works good. Fuchs titan etc. 1.5qts capacity
The maintenance manual has the frequency of changing schedule. But if yours is an 06 it is due.


really seemed to benefit from it. I used 75w90 mobil1. Plenty of people have used it with no problems.
Call me naive but, aren't they the same thing?
http://www.amazon.com/Silkolene-Medi.../dp/B00330M55C
http://www.carpartsdiscount.com/auto...3681&3671=1002
the living tards out of you and make you want to use the MB spec oil.https://mbworld.org/forums/e-class-w...il-change.html





