[achilleas_p87]

Hi guys,

This is my first post so please bear with me . so, i have an e93 2007 320i from 2012.My rims are 20 inch and people tell me this is very bad for the car though i dont mind the lack of power neither am i a heavy footer and the car was running very good in my opinion without any sounds for 5 years in my ownership.last year my rear differential (pumpkin ) broke after several warnings.My engineer said it was due to the never-changed-so assumed-life time oil in it.anyway, i swapped it with a used one and my engineer told me he refurbished it.after installing it i noticed a humming noise at over 80 kph and i liken it with the sound of what you hear underneath a bus as it accelerates.anyhow my engineer told me that its normal after such a swap so i let it be.fast forward a year now , the pumpkin makes a grinding sound as well and i noticed a leak of oil.i took it back to the mechanic and he told me that he fixed the sealant and added back oil but the sound still remains.he told me that to eliminate this sound i must insert a special oil or something and he insisted on the size of my wheels.what do you guys think? my thought is that i should replace this differential too . also i am afraid of a wrong ratio inserted.my car was perfect before the swap and i have spent a lot of money on it so it could be better to had taken it to dealership.also i have noticed that differentials are the achilles hill of the e9x. is there any strenghtened parts in order to tackle this issue? really love my car but this part is killing me.sorry for the volume of information and questions but i m sure that represent a very high percentage of the e9x owners.thank you all in advance and looking forward for your reply.

[Youngjnr]

Having same problem did u get it sorted

[JuniorB]

I believe there should be a sticky on lifetime oils in a car, as well as 100k plug intervals changes. Ic e been wren Hing for years and still laugh when I see lifetime on shit, even with synthetic fluid. Ever notice the lifetime fliuds are in clutch packs that burn and wear? Lol, like trans and diff's? But the don't say lifetime oil lol. The only lifetime fluids are sitting on a shelf unopened.

[JuniorB]

Sorry, what I meant to say is that I've been wrenching for years and still laugh when I see lifetime time fluid.lol

[PhaseP]

If the replacement diff was making noise from start it was already worn out. I am afraid you will need another diff. This time if it makes noise after replacement don't accept it. If used one ask for another used one. Used ones comes with some short warranty usually because nobody knows their exact condition until installed and working.

[Mavus]

If you hear grinding noise from the diff most likely you need new diff bearings. I had the same issue at 90k mi and bought new oem bearings. Diffs are not a weak point on these cars if you maintain them.

Make sure you go to a shop that has experience repairing and replacing diffs. Bearings cost around $300.

GL

[PhaseP]

Where or how did you find the oem bearings? Do they have available part numbers on them?
Also diff rebuild will require knowing the preload and backlash specs, don't think these published for these diffs. Specialized diff shops may have that knowledge, but the price may not be worth vs trying a used one with some warranty on it.