E32 Differential/final drive input seal

[Baal]

I was wondering if there was any place that had info on how to replace this seal. Mine is leaking like a sieve and my rear diff makes a whirring sound when I'm driving and remove my foot from the accelerator. The previous owner said that his mechanic said (sound suspicious?) that the reason for the noise is that the rear diff is low on fluid but that it will not affect the life of the car (sounds really odd to me, luckily i got the car REALY cheap because of it's problems, as you can tell from my other posts) anyway i found how to replace the output seal but absolutely no info on how to replace the input seal.

[lincolnmaster80]

If you do add or replace the rear diff fluid, DO NOT...I repeat...DO NOT USE SYNTHETIC OILS. These car's weren't designed to use them in engine, tranny, or diff. regular 15w-40 is the best oil to use in the engine at least. I would follow what the manual says to the letter. Synthetic oil might be the cause of the whining in the diff...

Anyways, on with the diff seal...

you might find this read interesting...
http://www.nmia.com/~dgnrg/page_23.htm

[Baal]

Thanks for the tip with the Oil but i'v been using 10W 30 in the engine it's good to know that i should change it when i next do an oil change. About that link, It talks about the trany's output seal i was looking for the rear diff input seal unless i have to change both... anyway thanks for all the help.

[lincolnmaster80]

Haha, sorry about that. I was looking a both pages and copy pasted the wrong one. You don't have to change both if the other is fine, but if you wanted to for good measure, that never hurts too.

This might be closer to what you're looking for?
http://bmwe32.masscom.net/sean750/di...OutputSeal.htm

[Baal]

Thanks for the link but i meant the input not output seal thanks i'v already looked all over http://bmwe32.masscom.net/ and the other sites listed in your signature and found nada about the input seal. Thanks for all the help tho lincolnmaster.

[lincolnmaster80]

Well, then you have two options...
1. Be the first to do a write up yourself

2. head on over to roadfly.com or bimmerboard.com (both sites require free registration) and ask 'highline' about it.

I've looked too for an "input" seal and have found only references to an "output" seal on the diff...maybe it's not a common fault?

If you go to http://www.bmwfans.info and look up your car under original parts (you can enter the last 7 digits of your VIN to look up parts, should be under group 33) and tell me what the part number is so I can see what you are talking about cuz I'm interested.

I'll admit, my knowledge only goes so far. Sorry I couldn't be more helpful.

Thanks...

[lincolnmaster80]

I found SOMETING. First, you have to removed the rear diff and driveshaft mount...some say they have been able to remove just the rear input diff/driveshaft mounts with the exhaust in place, but I highly doubt it. You'll have to remove the exhaust before the driveshaft can be unbolted. After the exhaust is removed, you might then be able to move the d/s out of the way. After that, the input seal is a pig to work on, apparently.

I've heard some have been able to treat it like an output seal, but by looking at pictures of how the input and output seals are assembled, it looks different enough to be nothing like an output seal.

You have to removed the d/s mount on the diff side and you have to remove all the other parts inside (obviously) with some sort of puller...

The part number I believe you want is this: 33 12 1 213 949

If you haven't seen it already, here are the inner parts that the diff's input has inside...just so you know what you're looking at.

http://bmwfans.info/original/E32/Lim...3/ill-33_0073/ (keep in mind, this link is for my 02/1990 production 750iL...it may differ from yours)

The actuall removal I'm not too sure with. It's odd that there wouldn't be a write up of some sort. I have to look at the input on my diff in a few days (not the seal) and I can take some time and pics on how to remove it if you like?

[dlog]

Not that I'm saying your wrong, but I was told by a BMW dealership that if I didn't use the BMW dealership oil the next best thing was Castro Syntec 5W-30. And for the Differential noise to go away, to use redline differential fluid. So far everything is fine???

[lincolnmaster80]

Realistically, I guess it comes down personal choice, but the manual makes no mention of using synthetic oils. It does, however, make mention of using "special" oils in cases where regular oil is not readily avaliable, and may be used only for top ups. These special oils might be refering to synthetics, but I don't know. This comes right out of my E32 manual that originally came with a 1994 740.

You have to keep in mind too, that even though they are "BMW mechanics", they still are subject to their own personal "knowledge" and opinions. One mechanics answer will no doubt be a little different than another mechanics (as will be different from my answer ).

My dad had a 89 Jag Sovereign. He sold it to a guy who followed the advice of a mechanic who recommended that he use synthetic oil in the diff. After the diff oil change, the diff started to howl at low speeds and didn't stop when going faster. Funny thing was, my dad told the new owner to not use synthetic in ANY part of the Jag. When he was looking at the car, the new owner asked what oil my dad used and basically said, "OH MY...I'll have to fix that then..." I believe the Jag manual even said in bold letters, "DO NOT USE SYNTHETIC OIL". Suffice of to say, he changed the oil back to regular diff oil and the howl went away.

I think the auto transmission in that Jag is the same auto tranny in my 750, and if I'm not mistaken, is also the same in the 735's.

15w-40 has the best lubrication properties for summer time driving for the motor over any other motor oil (I use 0w-10 in winter). Most of the race cars my dad has been around and worked on at Bonneville have never used synthetic oils...if that tells you anything.

But like I said, it's up to you how you want to take care of your car. That's what makes our cars unique and special to us. I honestly don't see a benefit to synthetic oils. I have tested them in the past on my Fords and there was no difference in performance or lifetime of the oil. It looked just the same after 3000KM's. If anything, it seems to be just a hype and a money grab...