[parksjm7]

Rear Differential Fluid change

E92 2007 335i RWD build 9/2006

69,800 Miles

Preface:
So I understand the OEM fill is Castrol 75w-140, but the concensus seems to be that if there isn't any track duty involved,(or even light track duty) a quality 75W-90 would suffice. (EDIT: OEM Fluid SAF-XO IS 75w-90 credit @kkasson )I'm all for using lighter oils, but using a oil with -50 less weight didn't sit right with me (although if I blow the diff, it's a good excuse to go LSD) so I got the Amsoil Severe Gear 75W-110. Can't remember the publications, but I've read through a number of comparison articles showing Amsoil came out on top (it used amsoil 75w-90, which I understand is somewhat of a class below, since it isn't classified "Severe Gear" by Amsoil).



Being a bit OCD on this stuff, I sourced a few things before I began -

Fluid Transfer pump from Harbor Freight:



10QT measuring container from Home depot (to be used for Transmission fluid drain and fill later which is ~6QTs)



Got pretty much exactly 1QT out of the diff case after opening it with a 14MM hex bit and breaker bar - How does the fluid look? I've no clue if this fluid looks good or not..



New fluid - measured a bit more than the old fluid that came out, but a little bit leaked because the cheap transfer pump wasn't upto the task, so I was okay with the quantity. Much clearer than the old fluid for sure but again, I've no idea:



When I do the transmission fluid, I'll source an electric transfer pump like this:



Of course placebo biased my impressions - but from a short drive, I feel that the friction at lower revs / speeds are reduced, whether it be due to the lighter weight oil or simply new fluid instead of old, or both.

Anyone else used Amsoil / lighter weight diff fluid? I'd like to see how you guys feel about your choices, as well as what you think about the 75w-110.

[kkasson]

I think 75w-140 was only used for the LSD in the M3. It's Castrol SAF-XJ. Non-M used Castrol SAF-XO which is 75w90. (Castrol stopped selling this fluid but it's still available from the dealership, as well as from BMW motorcycle dealerships as final drive fluid)

In any case, the Amsoil is probably still fine.

[LaChewy]

How many miles on the car?

[parksjm7]

Originally Posted by LaChewy

How many miles on the car?

~69,800.

[LaChewy]

Yeah dude that diff is a baby. I'd treat it like one. Drain it again and use royal purple.

It's worth it to use the correct weight. Plus you already bought a transfer pump and you can reuse that mofo.

I don't know about you noticing a positive difference in performance from the fresh oil. I've never felt a noticeable change after an preventative diff change - you might be wishful imagining. Or "Placebo biasaed"

The old oil didn't look too bad, but good timing either way.


It seems like you're saying you took the whole face off the pumpkin, if so, and you decide to take my advice to re-fill with the proper weight, consider just going through the fill hole this time instead.

Pump out the old and pump in the new through FILL HOLE.

Make sure car is jacked up level and pump new oil in until it over-flows out the hole.


Don't crack the face open again after it's been torqued back to spec.

[Zajac1]

How many qt of diff fluid u used ?? One is enough ?? I'm planning to replace transmission fluid and I red it's good to replace diff as well especially when i got almost 100k on odometer.
Btw. May I use that tool for diff ?
https://www.ebay.com/itm/Automotive-...0AAOSwjodaAJjo

[parksjm7]

Originally Posted by LaChewy

Yeah dude that diff is a baby. I'd treat it like one. Drain it again and use royal purple.

It's worth it to use the correct weight. Plus you already bought a transfer pump and you can reuse that mofo.

I don't know about you noticing a positive difference in performance from the fresh oil. I've never felt a noticeable change after an preventative diff change - you might be wishful imagining. Or "Placebo biasaed"

The old oil didn't look too bad, but good timing either way.


It seems like you're saying you took the whole face off the pumpkin, if so, and you decide to take my advice to re-fill with the proper weight, consider just going through the fill hole this time instead.

Pump out the old and pump in the new through FILL HOLE.

Make sure car is jacked up level and pump new oil in until it over-flows out the hole.


Don't crack the face open again after it's been torqued back to spec.

Re: Royal Purple, I've heard some good things about it earlier on, but I'll try to find the comparison test that showed otherwise, that swayed me away from it and going with Amsoil instead. EDIT: Here it is - hopefully this test was not placebo-biased http://www.lastgreatroadtrip.com/wp-...comparison.pdf

About the Fill hole - yeah now that I read my post again, it does sound like I opened up the diff. The 14mm hex bit was used to open the fill hole - the face of the pumpkin was not opened.

Originally Posted by Zajac1

How many qt of diff fluid u used ?? One is enough ?? I'm planning to replace transmission fluid and I red it's good to replace diff as well especially when i got almost 100k on odometer.
Btw. May I use that tool for diff ?
https://www.ebay.com/itm/Automotive-...0AAOSwjodaAJjo

I don't think this tool will work to drain the old fluid out. You'll be able to put in the new fluid, but you want one that'll work both ways - unless you fit a flexible hose on the vacuum end. Honestly, I'd go with an electrical transfer pump like the one I posted up. I found it on ebay for about ~$9. The fluid is very thick and you won't have an easy time transferring the fluid in / out with a non-powered pump.

I believe the capacity is ~1.2qt. I drained out only 1qt and refilled it.

[Zajac1]

Originally Posted by parksjm7

Re: Royal Purple, I've heard some good things about it earlier on, but I'll try to find the comparison test that showed otherwise, that swayed me away from it and going with Amsoil instead. EDIT: Here it is - hopefully this test was not placebo-biased http://www.lastgreatroadtrip.com/wp-...comparison.pdf

About the Fill hole - yeah now that I read my post again, it does sound like I opened up the diff. The 14mm hex bit was used to open the fill hole - the face of the pumpkin was not opened.



I don't think this tool will work to drain the old fluid out. You'll be able to put in the new fluid, but you want one that'll work both ways - unless you fit a flexible hose on the vacuum end. Honestly, I'd go with an electrical transfer pump like the one I posted up. I found it on ebay for about ~$9. The fluid is very thick and you won't have an easy time transferring the fluid in / out with a non-powered pump.

I believe the capacity is ~1.2qt. I drained out only 1qt and refilled it.

For diff I bought Redline 75W90 and for transmission Redline D6 ATF. It takes to long to get that pump out from ebay. I need to buy similiar to it in some store, but don't know where to look for.

[mweisdorfer]

Originally Posted by Zajac1

For diff I bought Redline 75W90 and for transmission Redline D6 ATF. It takes to long to get that pump out from ebay. I need to buy similiar to it in some store, but don't know where to look for.

When I dropped the rear subframe & differential last spring to change my subframe & diff bushings, I tipped the differential upside down & drained the oil out. I got about 40oz out. I have also used an air powered brake vacuum (mitivac) to suck the differential fluid out and have got around 40oz out that way too.

I know it's only 8oz, which is not a lot.

[parksjm7]

Originally Posted by mweisdorfer

When I dropped the rear subframe & differential last spring to change my subframe & diff bushings, I tipped the differential upside down & drained the oil out. I got about 40oz out. I have also used an air powered brake vacuum (mitivac) to suck the differential fluid out and have got around 40oz out that way too.

I know it's only 8oz, which is not a lot.

Yeah, I couldn't justify buying another quart to do a complete flush for the remaining 8 oz, but i'll probably buy the amsoil 75w-90 next year and change another quart out. Like you, I'm looking to use the amsoil ATF for the transmission fluid as well so this was a but of a dress rehearsal if you will.

Can you offer me some advice on changing the ATF? I'm not planning to change the pan, just whateverfluid I can drain out which I believe is about 5 qts.

[mweisdorfer]

Originally Posted by parksjm7

Yeah, I couldn't justify buying another quart to do a complete flush for the remaining 8 oz, but i'll probably buy the amsoil 75w-90 next year and change another quart out. Like you, I'm looking to use the amsoil ATF for the transmission fluid as well so this was a but of a dress rehearsal if you will.

Can you offer me some advice on changing the ATF? I'm not planning to change the pan, just whateverfluid I can drain out which I believe is about 5 qts.

You can pull the transmission cooler line and flush the entire 9 quarts, torque converter included, out of the complete system. You just need a buddy to start and stop the motor while you monitor how much flows out into your "used amsoil transmission oil bottle", which conveniently has the measurements on the side.

Take 3 quarts out. Put 3 quarts in. Do this until you have flushed about 10-12qts through the system. It should be bright red when it's all said and done.

You of course change the pan out before doing this process and you will need the special tool to pull the line. You can get one for about $13.00 from FCP Euro.

You just need to pull the line that is warm. The line that is cold it is returning ATF to the Trans. You want ATF coming from the trans, which would be warm.

I use the fuel efficient ATF in the blue bottle.