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Discussion Starter · #1 ·
So the other day my rear differential started clunking/popping loudly every time I turn even remotely sharply, it will not pop if I turn at a big angle. I'm thinking maybe one of the teeth broke off. I don't know the course of action as to how to replace a rear differential. I could not find any DIYs online and am not sure how difficult a job this is. If anyone could help guide me in the right direction as to what would be the best course of action. Or how long a job like this could take (I have zero experience). Thanks for your time
 

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I have zero experience
What comparable mechanical work have you done? I can’t offer any guidaance but the answer to this may help someone else give you a better answer to your question.

I had a rear differential seal leak that was discovered last month - the seal replacement cost $1500 or so at the dealership. There were no mechanical symptoms. A trusted shop doing an alignment brought it to my attention.
 

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Has anybody told you it was the rear diff or is that your diagnosis? I’d hate to see someone spend a lot of cash to not fix a problem.
I ask as F30 rear diff failure isn’t super common as they are replaced as units. Normally if one fails prematurely someone recently did a pinion seal and over tightened or under tightened the pinion nut which screws up the pinion bearing preload and potentially messes with pinion to ring gear depth/backlash if it’s way off.
 

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So the other day my rear differential started clunking/popping loudly every time I turn even remotely sharply, it will not pop if I turn at a big angle. I'm thinking maybe one of the teeth broke off. I don't know the course of action as to how to replace a rear differential. I could not find any DIYs online and am not sure how difficult a job this is. If anyone could help guide me in the right direction as to what would be the best course of action. Or how long a job like this could take (I have zero experience). Thanks for your time
How about differential bushings?


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Discussion Starter · #5 ·
Has anybody told you it was the rear diff or is that your diagnosis? I’d hate to see someone spend a lot of cash to not fix a problem.
I ask as F30 rear diff failure isn’t super common as they are replaced as units. Normally if one fails prematurely someone recently did a pinion seal and over tightened or under tightened the pinion nut which screws up the pinion bearing preload and potentially messes with pinion to ring gear depth/backlash if it’s way off.
I think I should also I add I have done quite a bit of donuts with the car, it didn't happen when I was doing them. I was just driving and I started noticing it. Also jiffy lube diagnosed it for me they said the oil in there was black and had never been serviced and also had quite a bit of metal flakes in it.
 

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I think I should also I add I have done quite a bit of donuts with the car, it didn't happen when I was doing them. I was just driving and I started noticing it. Also jiffy lube diagnosed it for me they said the oil in there was black and had never been serviced and also had quite a bit of metal flakes in it.
You really should consider having either a BMW dealer or good BMW independent repair determine what the problem really is. Right now you are guessing. They may be able to repair or if the differential is shot then they might be able to find a good used one. Jiffy Lube would not be my choice.
 

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In your diff is a ring gear that spins at the speed of your rear wheels. Connected to that is the pinion which houses the side gears as well. All of these spin when you turn even a little. The fact that you can turn sharply and it happens but turn gently and it doesn’t makes me think it may not be the diff. If you had an LSD I could see the clutches binding on sharp turns but F30 should have a normal open diff unless you got the M sport diff somehow. I’d get a second opinion to confirm before buying a new rear diff.
Also the fluid will be black if you’ve never had it serviced. This is not necessarily an indication of a problem unless it smells burnt.
usually diffs fail by simply internally exploding or making a bearing type noise. I’ve seen a few odd balls like what you mentioned but it’s not the norm.
 

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Find an independent shop that has experience rebuilding differentials.

They should be able to tell you if it can be diagnosed and rebuilt. Not sure if you need a BMW mechanic for this.
 

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I think I should also I add I have done quite a bit of donuts with the car, it didn't happen when I was doing them. I was just driving and I started noticing it. Also jiffy lube diagnosed it for me they said the oil in there was black and had never been serviced and also had quite a bit of metal flakes in it.
Runs to the donut shop with your car? Or bake donuts? Or youve been abusing the shit out of the car?

Yeah, just go buy a new diff and have at it- post up any questions and Im sure someone here will be able to get you through it, and back to donuts again.
 

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Discussion Starter · #10 ·
Runs to the donut shop with your car? Or bake donuts? Or youve been abusing the shit out of the car?

Yeah, just go buy a new diff and have at it- post up any questions and Im sure someone here will be able to get you through it, and back to donuts again.
Can you specify what you mean in the first two questions? But you live and you learn obviously won't be doing them again
 

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Runs to the donut shop with your car? Or bake donuts? Or youve been abusing the shit out of the car?

Yeah, just go buy a new diff and have at it- post up any questions and Im sure someone here will be able to get you through it, and back to donuts again.
Pack that differential with chocolate glazed donuts and broken tooth gaps will fill right up.
 
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