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Rear Differential Fluid Replacement
 
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Pelican Technical Article:

Rear Differential Fluid Replacement

Nick Czerula

Time:

1 hour1 hr

Tab:

$30

Talent:

*

Tools:

14mm Allen bit, drain pain, oil quart container pump

Applicable Models:

BMW 323Ci Coupe/Conv (1999-00)
BMW 323i Sedan/Wagon (1999-00)
BMW 325Ci Coupe/Conv (2001-06)
BMW 325i/xi Sedan/Wagon (2001-06)
BMW 328Ci Coupe (1999-00)
BMW 328i Sedan (1999-00)
BMW 330Ci Coupe/Conv (2001-06)
BMW 330i/xi Sedan (2001-06)

Parts Required:

Differential oil, differential plug sealing washers (2)

Hot Tip:

Drive car for short distance to warm oil

Performance Gain:

Extend differential life

Complementary Modification:

Use Swepco transmission fluid for better shifting

The rear driveshaft transfers the rotation of the transmission (or transfer case) output shaft to the input shaft of the rear differential. Inside the differential, the axis of rotation is turned 90 degrees. Using specially designed planetary gears, the differential also splits the power in order to accommodate cornering: the two rear wheels must be allowed to rotate at different speeds in a turn. The output flanges of the differential connect to the drive axles, which power the rear wheels.

The oil in your rear differential is considered lifetime by BMW. This does not mean you shouldn't service it. When a vehicle manufacturer refers to a component as lifetime, the time period is usually 100,000 miles or so. So your differential oil lifetime is 100,000 miles, what does this mean when it comes to servicing? The oil in the rear differential lubricates the bearings and gears that drive the rear wheels of your E46.

You want these items to last, and with routine maintenance, they will. I suggest replacing your differential fluid every four years regardless of mileage. It's a good idea to check the fluid every time you change your oil and top it off if necessary. Your rear differential will hold about one liter (M3 models 1.5 liters) of oil, but have a little more on hand in case you spill it.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Checking fluid level
First, drive vehicle for about 2-3 minutes to warm the differential oil.
Figure 1

First, drive vehicle for about 2-3 minutes to warm the differential oil. Next, lift and support the front and rear of the vehicle. You want the rear differential to be level when checking the oil level. Working at rear differential: using a 14mm Allen bit, remove the oil fill plug (yellow arrow).

Next, insert your finger into the fill hole, oil level should be at the bottom of fill plug opening.
Figure 2

Next, insert your finger into the fill hole, oil level should be at the bottom of fill plug opening.

Replacing fluid
Working at rear differential: using a 14mm Allen bit, remove the oil fill plug (green arrow).
Figure 3

Working at rear differential: using a 14mm Allen bit, remove the oil fill plug (green arrow).

Next, using a 14mm Allen bit remove the differential oil drain plug (green arrow).
Figure 4

Next, using a 14mm Allen bit remove the differential oil drain plug (green arrow). Drain the oil into a suitable container with a 2 liter capacity. Once the oil has completely drained, reinstall the drain plug with a new gasket and torque to specs.

Pump the oil into fill plug hole until it runs out.
Figure 5

Pump the oil into fill plug hole until it runs out. Allow oil to stop dripping or come to a slow drip, then reinstall fill plug and torque to specs.

This photo shows M3 model rear differential fill (green arrow) and drain plug (yellow arrow) locations.
Figure 6

This photo shows M3 model rear differential fill (green arrow) and drain plug (yellow arrow) locations.

Once finished, take vehicle for a short ride and check BMW rear differential for leaks.

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Comments and Suggestions:
ajp340 Comments: I'm hearing a "hoot" sound when the car changes from 1st to second.

check it out:
https://www.youtube.com/watch?v=xcqC37m63hU
October 2, 2016
  Followup from the Pelican Staff: If only doing it is first to second, I would assume it is inside the trans. If it is does it other times, look for a, air leak or faulty crankcase vent. - Nick at Pelican Parts  
DJLilBASTaRd Comments: So I put the oil in rear differential it literally makes a sounds like two guys smashing pipe wrenches against the concrete. and the faster I get a lil better it gets so what do I need all the parts to fix the rear differential what am I looking at here thx 1!1
May 30, 2016
  Followup from the Pelican Staff: It depends. I would assume the bearings and gears are faulty, from the sound you described.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
DJLilBASTaRd Comments:
. Have a 2003 325 I sports wagon I know it's been leaking oil from the rear differential for some time now I just got oil for it but I couldn't find a 14 millimeter Allen socket anywhere so I had to go to play a booking in Arizona as I was headed out there and beat some little rice rocket Jap crap car and right after the race I end up hearing a hissing sound and the car didn't quite feel right pulled over to the side of the road it was smoking so bad inside the cabin outside the cabin I let it cool the car started no problem shifting into gears no problem as I was going forward it felt like I was dragging my muffler on the ground but it shifted into drive no problem and I have been able to hobble to the gas station and I'm sitting here now wondering if I add the oil to it will I be able to drive it or do you think I caused too much damage to it and I'll have to replace it
May 27, 2016
  Followup from the Pelican Staff: No clue. You have to figure out where the smoke came from. I would tow it to a shop. - Nick at Pelican Parts  
bkl070 Comments: Dan I think they missed your question. Rear differential where the driveshaft enters? I know there are oil seals there.
March 24, 2016
  Followup from the Pelican Staff: Correct, it could be the diff seal. Output or input seals are possibles. I read his his note as a leak in the front center of vehicle, maybe our wires were crossed. Thanks for the help with this one. - Nick at Pelican Parts  
Dan Comments: I have oil leak in my differential 06 325i ..at the front center location.do you have an idea how to fix it..ty
March 12, 2016
  Followup from the Pelican Staff: You'll have to pinpoint the source. It could be the oil filter housing, the valve cover, a hose, etc. Start here:
http://www.pelicanparts.com/BMW/techarticles/tech_main_e90.htm #engine - Nick at Pelican Parts
 
Ahmed Comments: The capacity of rear differential oil e46 2002?
January 10, 2016
  Followup from the Pelican Staff: Your rear differential will hold about 1 liter (M3 models 1.5 liters) of oil, but have a little more on hand in case you spill it. - Nick at Pelican Parts  
bill Comments: how much oil does the rear for a 2004x3 hold
December 18, 2015
  Followup from the Pelican Staff: I would need to know the year and model of your vehicle to check if I have that info. - Nick at Pelican Parts  
Pete Comments: Comments: Hi Nick,

Reading through online posts I'm think that changing the Rear Diff. Oil on my E46 320i auto tourer may solve an issue I have:

I keep hearing an intermittent humming sound that lasts 1-2 seconds then dissappears - like i'm driving over road markings at the side of a freeway. Its usually followed quickly with jumpy revs, as if the auto gearbox is trying to switch gears but can't make up its mind. It happens at 30-40 mph, and sometimes at higher speeds but dissappears if I push the accelerator.

This has not happened before, and I've had the car a good couple of years and I'm worried its something serious. From reading some of the online posts I think this is problem other owners have experienced - a few recommendations have focussed of changing the Diff. oil, do you think this will solve the issue, and what else could I try?
October 7, 2015
  Followup from the Pelican Staff: This could be a slip caused by low fluid or low pressure. Start by checking your fluid level. If it is OK, you may have worn parts causing a pressure drop and slip. I would have it checked before it gets much worse.
- Nick at Pelican Parts
 
targa996 Comments: What is part number for fill and drain plug gaskets on diff ? ALso is Redline 75W90 diff fluid OK - or what is recommended other than dealer fluid here - I don;t see diff fluid listed on your site only trans ?
August 21, 2014
  Followup from the Pelican Staff: I don't have the part numbers handy. Our parts specialists will. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 

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Page last updated: Mon 12/5/2016 02:19:28 AM