Help please!!!

[1eyebandit]

Hello I have a 2014 650i M-Sport Convertible, I was returning home for running errands and heard a loud bang sounded like I hit something, the car was still running but the car didn't accelerate when I hit the gas and the engine just revs. I was able to coast home as I was right down the street. The car starts fine, I can shift to all gears and hear a noise coming from under the car while in drive and reverse, and the car does not move engine just revs. I pulled out the laptop fired ISTA and I have no codes, no CEL, no fluid leaking. I'm at a lost any help would be appreciated. Thanks.

[suj999]

Must be a gearbox issue

[1eyebandit]

I put the e-brake on jacked it up, put the car in drive the sound I hear seems to be coming from the rear differential. Any ideas?

[Kaizer84]

Maybe a broken axle somehow

[Kaizer84]

If the engine is reving but the car won’t move and you can get the car in gear etc it isn’t the gearbox, it’s more than likely an axle, especially since you heard a loud bang, axle must have broken.

[1eyebandit]

Kaizer84 Is there a way for me to check the axle to see if its bad?

[scubachris]

hi.
im not sure if your car is x drive or not..in the uk we dont get x drive.
the issue appears to be in the drivetrain after the transmition if that is working ok.

this leaves prop shaft joints seperated.
rear axle differential assuming not an x drive.
rear driveshafts.

i dont know if you have limited slip diferential or not..but if you can fire up the car,put transmittion into neutral then jack both rear wheels up off the ground..if you spin one back wheel and you have limited slip diff then the other back wheel will spin the same way.if not limited slip dif the other wheel will spin the opposite way.

a prop shaft joint would probably be the weakest link and easiest to fix..it would be likely to be the joint that bolts onto the gearbox as if it was the middle joint or axle end joint the broken prop shaft would still spin but flap about and make a terrible noise.

a local garage could easily diagnose this by lifting the car up on a lift.

best case a prop shaft joint £100 ish and one to two hours labour.

worst case rear axle diferential shot,a used one from a breakers yard £500 to £1000 and a full day to fit.
i would think it highly unlikely the gearbox is at fault as it is mostly electronic and you would have got a fault code..no fault codes for the torque converter though.

fingers crossed its a prop shaft joint..im not sure if thats correct us terminology..a proppelor shaft is the round drive shaft between the gearbox and the axle.

[Kaizer84]

Yea @scubachris he didn’t specifically mention Xdrive so I believe he has a rwd model. @1eyebandit if you jack the rear section of the car up you may be able to just look underneath and see the culprit, the axle may be snapped or just dangling out. Best way is to see if both wheels are slightly rotating when you put the car in gear. If not then your problem is your axle. You may just have to have the car towed to your mechanic or a trusted shop and they can diagnose the issue for you fairly quickly.

[1eyebandit]

scubachris No its not an Xdrive, I will go out and jack up the car, put it in neutral and see spin the wheel, I'll also look for a broken or damaged axle or driveshaft. I'll come back and report the findings.

[1eyebandit]

Soooo.... I got both tires off the ground started the car put it in neutral, both tire spin freely when I spin them by hand. both axles are nice and tight I see them attached to the differential no damage to the boot on the axles.

I started the car while lifted put it in drive, went under the car and I can see the driveshaft spinning but I hear a noise coming from the differential. (see attached video).

Do you guys/gals think I have bad differential?

https://o365ucr-my.sharepoint.com/:v...Lxa7w?e=iiFfkH

[Walt White Coupe]

Sure looks and sounds like it.

[1eyebandit]

Walt White Coupe Could the noise be from a bad cv axle?

[Walt White Coupe]

The drive shaft is turning and the wheels are not. The only thing between those two points is the differential.

[D'Mann]

Looks like the rear gears, or something in the differential, is busted. I got a rear diff for a 2012 550i off ebay for a couple hundred dollars 4 years ago. My issue was a different issue, but that saved a few thousand dollars over getting one from BMW.

[D'Mann]

https://www.ebay.com/itm/22574435924...3ABFBMgsiu_LFj

Here is one with a 2.81 ratio for $380 after shipping

[1eyebandit]

Originally Posted by D'Mann

https://www.ebay.com/itm/22574435924...3ABFBMgsiu_LFj

Here is one with a 2.81 ratio for $380 after shipping

Thanks, I ordered one on Monday off eBay, just waiting for it to come in. I hope it will solve my issue.

Thanks for the info!

[obtt]

How can you prevent this? Flushing the rear diff?

[D'Mann]

Originally Posted by obtt

How can you prevent this? Flushing the rear diff?

that depends on what broke inside. If the gears stripped out/broke It could be anything.

But checking gear oil level, and changing it at least at the prescribed intervals can reduce the likelihood of it happening.

[1eyebandit]

I have a 2014 f12, just hit 80k miles. I bought it used, i dont drive it hard, I didnt have any noise or anything to warn be before it happened, I should be getting my rear diff replacement today and I will update this thread with the findings.

[1eyebandit]

UPDATE - Took my car to the shop today, the differential was fine, the problem was the triangle shape flange that connects to it was just spinning. The replacement differential sloved the problem. Thanks to everyone who chimed in was some assistance, much appreciated.

[D'Mann]

Originally Posted by 1eyebandit

UPDATE - Took my car to the shop today, the differential was fine, the problem was the triangle shape flange that connects to it was just spinning. The replacement differential sloved the problem. Thanks to everyone who chimed in was some assistance, much appreciated.

Glad you got it sorted out.