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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Interesting observation for changing front diff oil



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      08-21-2015, 03:01 PM   #1
ajsalida
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Interesting observation for changing front diff oil

Getting ready to change F/R diff oil and transfer case fluid this weekend. While I was doing a R&R of the intake manifold recently I noticed something that might make the front diff fill much easier.

With all the filters, charge pipe etc. out of the way, the fill plug is right there with easy access from inside the engine compartment. I had to reassemble everything to finish that job but today I decided to clean and re-oil my DCI filters. Confirmed that with only the front filter off but CP, DV's, etc still in place, I could still get unobstructed access to that top fill plug.

As far as the TC fluid, looks like the easiest thing to do is remove the cross brace to get at the fill plug, while supporting the case from below with a jack. No cutting off a 14mm allen wrench and squirming around under the car to get 1/10th of a turn. Pelican has a DIY on this procedure BTW.

Will update once I get it all done. If anybody knows for sure either of these will not work please advice.
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      08-22-2015, 05:51 PM   #2
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Well I did the front diff. The fact that you can get at that fill plug from the top vs the bottom was not a big deal either way. I ended up using an ordinary 14mm allen wrench from the bottom, long end goes straight in from the side. With a 14mm box wrench slipped over it no issues getting to the the fill plug. You can get 1/4 to 1/2 turn each time to get it unseated, then use your hand rest of the way. Pretty easy.

HOWEVER...I cannot claim I was smart about this next part, just lucky. I drained the front, let it drip into the pan, went to the back. You have to suction out the back, no drain plug just a fill plug. Both my @$#%%!!# hand pumps don't work! Seals must have gone bad sitting, could not pump any fluid at all. I am so lucky I did not drain the TC, because the only way I could fill the front diff was from above, through the engine compartment, using a long hose on the end of a quart of gear oil. You can easily see when it is full from up top, and then pinch the hose and not lose too much fluid.

So will need to get a new hand pump before I hit the rear diff and TC. Lesson here is confirm hand pump works before draining. Mine worked last year when I changed diff and tranny fluids in my other car, go figure.

Last edited by ajsalida; 08-22-2015 at 05:57 PM..
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      08-24-2015, 09:18 AM   #3
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I had done the front diff by removing the driver side wheel to access the fill plug and that reinforcement plate to access the drain, if I remember correctly on that last part. I had used a 14 mm socket with six inch extension for the fill plug reaching from the wheel well.

I had done the transfer case without removing the transfer case brace. The challenging part for me was to thread in the fill plug back in. Used a magnet pick and some other combination to get it going. I later for some other work removed the transfer case brace. There is a long bot thats get blocked by the exhaust pipe which makes it challenging to remove. You need a jack to support the TC but that is not much difficulty. When putting it back, I put that bolt from the other way, as I had seen in one of the Pelican or RMEuropean videos. So next time it will come off easy if I need to. Even though removing the brace is that easy (unless exhaust is removed out of the way), if I have to do the TC case oil change now, I would go that way. Because while trying to thread in the fill plug I was worrying that some dirt and sand that was hanging there would go into the TC while trying to push in the plug up there not being able to see and it keeps falling and so on when doing it without removing the brace..

As a side note, the bolts on that bottom reinforcement plate under the engine are one time use, like many others on this car. And such replacement bolts and nuts can get expensive if one follows the book. They are torqued to stretch up to some angle. Because they need to come of for so many common things working on this car, I had reused the bolts couple times, but one time I got a new set.
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      08-24-2015, 09:34 AM   #4
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I did not need to take the wheel off, but same idea with the front diff fill plug. Straight in from the side with the long end of an ordinary 14mm allen wrench + box wrench, no issues.

I did not know those bolts on the reinforcement plate were one-time use, are you sure? I must have removed them 20 times already doing various things under there, and they are pretty stout. Oh well.

Plan to tackle the TC later today after I get a new hand pump. I think you can get the long bolt out without dropping the exhaust, see #5 here, if not no big deal:

http://www.pelicanparts.com/BMW/tech..._Replacing.htm
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      08-24-2015, 11:46 AM   #5
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I am pretty sure those are one time torque to yield one time bolts. I reused a few times, then one time replaced, then reused.

The strut brace bolts on the top in engine bay are also torque to yield one time bolts. I don't think people are replacing them either. I did replace them one time, last time I haven't yet, reused. Of course I don't torque them to yield again to the spec when reusing.

I was able to remove that TC mount long bolt without removing the exhaust, but I had to drop the TC a lot and still was a struggle. During assembly they must have put it before the exhaust goes on. It is doable, just some challenge on the way.
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      08-25-2015, 11:02 AM   #6
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I looked at your Pelican link more carefully now, they are saying that long through bolt doesn't have to come out fully to get the brace down. I wish I had known that at the time

I even had to disconnect the bracket that secures the exhaust to the TC with two small bolts there in order to be able to push the exhaust as much as possible out of the way to get the bolt out.

But even with the bolt out, pulling down the bracket wasn't simple either. It could be that I had the TC down too much making it not aligning well. And being on my back on the ground with not much clearance was a contributor.

Everything goes in easier though, as usual, at least for me. Rust and corrosion is already broken off.

Good to know the brace comes down with the bolt like that.
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      08-25-2015, 12:31 PM   #7
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Just FYI, my diff fluid was fine at 120k miles.

I only ended up swapping half the fluid in each diff.

The fluid was clean and had very little metal shavings in it.
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      08-25-2015, 01:11 PM   #8
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My car only has 42k miles but I'm trying to diagnose a noise from the driveline. Wanted to rule out the diffs + TC first as changing the oil and inspecting fluid is "easy".

Front fluid looked almost new, no shavings or deposits. However, it was low, at least more went in than came out. Noise is less but still there. I thought maybe wheel bearings or CV joint but turning by hand no noise.

The tension strut bushing is blown driver's side, oil leaking everywhere so I have to do that. I hope it is not either an axle or wheel bearing. I'll do the TS bushings after a bit.

Can't find a decent hand pump in my little mountain town, but once I get one next up is the transfer case + rear diff fluid. Then the TS bushings (replace with poly Strongflex), and hope nothing else is bad.
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      08-26-2015, 07:58 PM   #9
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Minor update here. I still have not been able to get a fluid pump but I think I did track down the noise. It ended up being a tire, LF. This was confusing because I had a similar but louder noises from a prior worn out set of Conti DWS. This noise however was mostly LF and sounded like a wheel bearing or CV joint. I had bought a nice low mileage wheel/tire set off eBay used and I think the PO's markings on the tires for LF/RF were wrong. Swapped the front tires/wheels side-side and the noise went away. So I may have been running them backwards from their wear pattern. These are Conti DW's so not directional.

I will still change TC and rear diff fluid when I get the pump. And I have to replace tension strut bushings as L side is blown, as soon as my friggin' hydraulic press shows up.

Question: does anyone know if the control arm (aka wishbone) inner bushing is fluid filled? I know the big bushing on the tension strut is. Reason I ask is I have an odd grease splatter pattern right over the control arm bushing, inner CV joint boot and rear upper part of the tie rod boot. It seems too far away from the TS bushing, but that bushing is also covered with a lot of grease. I can't figure how the grease got blown out to the front. Though maybe multiple raise/lower off of a jack squirts it out, and then the CV joint spinning slops it around. It is thick axle type grease, not diff oil or PS fluid, same as what is coming out of the TS bushing. The CA inner bushing is right there though.

I've very carefully gone over the CV and tie rod boots, no cracks or holes in them. No leak at the diff seal. Each time I look at the area though there is more grease there. I've looked closely at the CA bushing and I can't see any cracks or holes in the rubber, and frankly it isn't big enough to have this amount of fluid in it, if it is in fact fluid filled.

At least it appears I do not have to change a wheel bearing or CV joint/axle. It is possible/likely the blown LF bushing made the LF tire noise worse.
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      08-27-2015, 09:57 AM   #10
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I think it is grease filled, because it moves sort of like a ball joint, i.e. the arm can rotate along its axis to some degree in that "joint".
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      08-27-2015, 01:34 PM   #11
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Yep, I really did not fully understand before how that link moved. The end of the arm at the hub moves forward/back quite a lot when you turn steering lock to lock. I had thought it only rotates up/down about the axis of the bolt thru the bushing. So it is kind of like a heim joint in there, but obviously more compliant.
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      09-09-2015, 08:14 AM   #12
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I removed the 14mm drain plug no problem. The 14mm fill plug was more difficult to get to, but with a long extension and a big breaker bar and a u-joint, I cracked it loose without taking anything apart. Then it just unscrewed by hand. I was even able to get my torque wrench in there to tighten it.
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