What goes into the diff...?

[BMR BOY]

I (like you've read before) have been doing some preventive maintainence to my car, and I'm working on fluids too. The manual tranny in my '96 328i calls for Dexron II (idiots), and I've been approved by the dealer to use AMS OIL Synthetic Dexron III. However, when I asked the dealer what type of fluid was in the diff, they had NO IDEA! I was amazed. I am wondering what type fluid goes in my rear diff. If anyone has done it, let me know what you used. The dealership said "Well, maybe you can drain it and if it's red, it's tranny fluid, if it's not........well...........then I dunno." Boy, do I like answers like that!
BMR BOY

[Tim Polzin]

According to my 95 manual, the 325 takes 1.8 litre of name brand hypoid oil. Based on that, I used a 90 weight hypoid synthetic gear oil in mine. If you have limited slip, you might want to double check.

Tim

[dboyles]

I recently changed mine ('99 M3) out with Redline 75w90 gear oil. I'm not sure if your car has a LSD or not, but if not, use the 75w90NS (if you're going with Redline). FWIW, I ordered from www.myoilshop.com.

You'll also need a 14mm hex head wrench/socket that's capable of fitting into a tight spot. I bought a cheapo socket from AutoZone and took a cutting wheel to it (Pelican sells a tool that'll do the trick as well). And since you can't pour the oil from the bottle into the diff, you'll need some type of pump to do it. I got one from NAPA for about $6.

[Jeron]

dboyles is right about weight and special tool needs. Make sure to pull the fill before the drain. While your at it check the current level for piece of mind.

I used Royal Purple 75w-90. Only the M3 is LSD AFAIK.

[BMR MAN]

I second the use of Redline synthetic fluid for the diff. Depending upon the application, you can actually increase hp gains to the wheels by using synthetic. Theres an application guide to which weight you should use on redlines website.

As for where to buy redline, travis has an account at discount import and can get a discount on redline fluids, and they have it in stock (only place I know of that stocks it and is not online).

Btw, you like my username jon? haha

[BMR BOY]

Yes, BMR MAN, that is a great username. By the way, whereabouts do you live in P-town? Me and some buddies are planning a rally cross pretty soon if you want to tag along. I've heard good things about the Redline products, but it seriously DOES NOT get any better than AMS OIL. I can get it at my work (for cheap!) and it is the #1 in all tests. Also, I don't have to worry about putting it in. Oil Can Henry's will do both tranny and diff for $15. Saves me time and energy. Thanks for the input guys. So 75w-90 it is!
BMR BOY

[BMR MAN]

You know, I have heard thousands of great things about amsoil, but have really been lazy to actually test it. For now, mobil 1 and redline will do for me. And jon, this is matt...cant believe you didnt piece that together yet lol.

[knodb]

Amazing, a BMW dealer does not know what differential fluid goes into an E36. I think his memory would come around if you got your car in there an paid the $tealer $90/hr.

I am about to do a similar service on my 318i. I did some research on the 14mm hex socket and found one at http://www.tooltopia.com/browseproducts/SK-Facom-D10714-14mm-Male-Hex-Pipe-Plug-Socket---38--Dr..HTML . I have not used it yet but got this one because it is not as long as some of the other 14mm sockets I saw(i saw a picture of it on another site). I read on a post somewhere else that too long a socket may clash with the spare tire housing when using a torque wrench to tighten the bolt.

Since I'll be doing it soon I do have a question:

1) Are differential plug replacements necessary (or are there any gaskets I need to purchase ahead of time).

[Jeron]

There is a crush washer "gasket" but you can probably reuse the one on there. They are cheap at the $tealer less than 50 cents.

I think the clearance for the 14mm varies by model. The M3 is the smallest clearance. I bought a 14mm allen wrench, cut off about an inch and slid it into a socket.

Pull the fill plug before the drain plug.

[dboyles]

It's true, the clearance between the spare tire well and the diff on an M3 is minimal. Even with my cut-off socket, I couldn't get to the fill bolt with my torque wrench, so I had to settle for getting it guttentight courtesy of a box-end wrench and said 14mm socket. I also reused my washers (which didn't appear deformed at all) and haven't had any issues.

You can get to the diff no problem trouble without having to jack the back end of the car up. While I was waiting for the old stuff to drain, I jacked up the front to help everything along. After lowering the front and reinstalling the drain plug, I went to put the new stuff in via hand pump. However, clearance to work the pump was limited. So I put the back end up in the air, filled the diff until it started to overflow, then lowered the car (back to level) and allowed the excess oil to run out. Then I reinstalled the fill plug and cleaned up.

P.S. This was on Valentine's day, while my girlfriend sat on the couch. I'm pretty sure I am the punchline to a joke that starts, "You know you love your car when..."

[Jeron]

I jacked the front too now that you mention it. It drained a good amount more fluid. I dont think I used a torque wrench. It's not necessary. I just tightened it a little tigher than I do my oil drain bolt.

I also jack the left rear during oil drains, BTW. Good for at least 4oz more of motor oil.

[knodb]

To refill the differential (or tranny), would a turkey baster work in a pinch?

[Jeron]

Sure, so would a 1/2tsp. LOL

The fluid transfer pumps are only $5-7. A turkey baster will be very messy if it will work at all. You'd be better off with a partner standing beside the car pouring it down a long hose. I doubt there is enough room to even use the turkey baster.

Dont even try, get the pump.

[Dave at Pelican Parts]

My FLAPS (Friendly Local Auto Parts Store) carries "Marine Flush kits", which are a hand-pump that screws onto the regular one-quart oil bottles. Works well for quart bottles of transmission oil as well. If you buy the gallon sizes, there is a different pump (called something else, the name escapes me now) that screws onto the top of the gallon bottles. (Of Swepco in my case, but that's for the 914.) Works great for filling transmissions, which always seem to have the fill plugs located in very inconvenient places.

--DD

[BMR MAN]

Crush washers are very cheap insurance. They are only meant to be used once, I would replace them.