Grinding noise in D and R, no movement!

[16Alpina]

I'm a long time viewer, first time poster. So, I'm gonna get right to it, and hopefully I've posted this in the right spot.

I have a 2016 Alpina B6 (650i) with 80,xxx miles. I've owned it for 2 years and bought it certified from a BMW dealership w/ 70,xxx. The car has run strong and has never disappointed. However, when accelerating hard, I heard a pop, and the rpms almost hit redline before I let my foot off the gas. I then saw a small amount of smoke near the rear door/rear wheel area. I then noticed a grinding sound from under the car, which was relative to the rpms. As I gave it a little gas, the grind rpm increased, but the car did not move. I then tried reverse, which gave me a similar grinding noise, but at a faster rpm rate (probably because reverse is geared differently). This also did not move the car. The only time the grinding goes away is when the car is in neutral. I had it towed home on a flatbed.


Thanks,
16Alpina

1997 Z3
2004 M3
2016 Alpina B6

[ex46fanatic]

Sounds like you snapped the rear half shaft at the CV joint. Chill out with the launches. It's expected tbh if you stress that component often. You'll be ok.

[ex46fanatic]

I was considering just keeping a spare aside, they're not expensive used. Used to be aggressive with my 330ci E46 6 speed with LSD, broke 2 rear half shafts. After that I stopped.

[Opie55]

What is your plan with respect to investigating? Are you going to have it looked at by an shop, or you planning on crawling under there yourself? At this point we are just guessing. You either broke your transmission, your transfer case, or something external to both. Unless you really exploded something the transmission and transfer case will look normal. You can fairly easily see the front prop shaft that goes forward from the transfer case to the front differential. It has two fairly delicate looking U joints you might inspect. The rear driveshaft is a bit harder to inspect if your car is like mine, because it largely sits above the heat shielding for the exhaust system. But you see a good part of the ends. I also think it would move if you messed up one drive shaft but there could be some reason I don't know about. But if it's not the drive shafts, then pray it's the transfer case because that will not be cheap, but way cheaper than a transmission.

[16Alpina]

Originally Posted by Opie55

What is your plan with respect to investigating? Are you going to have it looked at by an shop, or you planning on crawling under there yourself? At this point we are just guessing. You either broke your transmission, your transfer case, or something external to both. Unless you really exploded something the transmission and transfer case will look normal. You can fairly easily see the front prop shaft that goes forward from the transfer case to the front differential. It has two fairly delicate looking U joints you might inspect. The rear driveshaft is a bit harder to inspect if your car is like mine, because it largely sits above the heat shielding for the exhaust system. But you see a good part of the ends. I also think it would move if you messed up one drive shaft but there could be some reason I don't know about. But if it's not the drive shafts, then pray it's the transfer case because that will not be cheap, but way cheaper than a transmission.

To be honest, I was hoping someone in the forum may have experienced the exact same situation and be able to tell me what I did, which would determine if I was going to lift it and remove all the splash shielding and bell housing skid plate to fix it myself, or just load it up and take it to the shop. I've done my fair share of DIY auto mechanic work over the years, so I would definately be able to find something broken if it's external (which between you and ex46fanatic, sounds like I could have done?). So, I will lift it and do some investigating myself and let you know what I find.

[Opie55]

Originally Posted by 16Alpina

To be honest, I was hoping someone in the forum may have experienced the exact same situation and be able to tell me what I did, which would determine if I was going to lift it and remove all the splash shielding and bell housing skid plate to fix it myself, or just load it up and take it to the shop. I've done my fair share of DIY auto mechanic work over the years, so I would definately be able to find something broken if it's external (which between you and ex46fanatic, sounds like I could have done?). So, I will lift it and do some investigating myself and let you know what I find.

If the car starts and runs normally, but when you put it in gear is just makes a bad sound and makes no attempt move at all, then my money is on internal damage to the tranny or transfer case. If those are both working, then the two outputs of the transfer case should spin. So unless you destroyed both the front and rear driveshafts simultaneously, it seems the car should move at least somewhat.

[tree]

Sorry to read about this. I believe there are 2 flex discs for the rear driveshaft. I have had one replaced on my 2016 Alpina because it had a few deep cracks. If that’s what failed, could be a relatively easy fix.

[ex46fanatic]

For rwd anyway, if one shaft snaps you lose all movement. Dont expect car to move with one shaft snapped, id guess its same for awd.

Only way we will know is when someone gets under there.

[16Alpina]

Thank you all for the feedback, it is much appreicated. I will dig into it and let all of you know what I discover....then ask for more guidance.

[16Alpina]

Well, here is what I've discovered. With the car fully suspended off the ground, I am able to freely spin each wheel, and in turn see the driveshafts for either the front or rear turn as well (depending on if I am spinning a front or rear wheel). Also, if I turn the driveshaft from the transfer case, it will turn both front tires at the same time (same happens when turning the rear shaft). However, at no time can I get all four wheels to turn together when only turning the front or rear shaft (maybe it isn't supposed to?).

Also, when I removed the front skid plate, I found that the front driver motor mount has failed and splattered oil all down the mount and onto the skid plate. Apparently if they go bad, they can cause multiple other problems if not fixed. So, that sucks! Not sure how that would impact the drivetrain like it has, yet the engine still runs smooth? Regardless, I have found one thing that needs fixed, and swapping a motor mount doesnt look like an easy task!

Lastly, when I started the car to turn off the parking brake and put it in neutral (so I could free spin the wheels), I shifted it into Drive first and I heard grinding for a split second, then it stopped and the rear driver tire began to spin (only one I could see). As soon as that happened, the park brake light on the dash started flashing and I got a "chassis stability" message on the screen. So, I quickly put it in neutral and turned it off. Any theories?

[Opie55]

You should swap motor mounts in pairs. It needs to be fixed, but it's not related to your drivetrain issue. It can cause vibrations because the engine is no longer isolated from the frame. I can't answer for sure which of your wheels ought to turn when. But turning one will not turn all four. The engine running smoothly doesn't mean anything. I would expect that. But at this point if you are convinced the car does not drive as it should and you have inspected the driveshafts, I'm not sure what option you have besides having it diagnosed at a competent shop. I'm not sure how people spitballing theories helps much at this point. It is likely something major, and it does not sound like you will fix it yourself even if one of us guesses correctly, and there is no way to know which guess is correct.

[16Alpina]

Originally Posted by Opie55

You should swap motor mounts in pairs. It needs to be fixed, but it's not related to your drivetrain issue. It can cause vibrations because the engine is no longer isolated from the frame. I can't answer for sure which of your wheels ought to turn when. But turning one will not turn all four. The engine running smoothly doesn't mean anything. I would expect that. But at this point if you are convinced the car does not drive as it should and you have inspected the driveshafts, I'm not sure what option you have besides having it diagnosed at a competent shop. I'm not sure how people spitballing theories helps much at this point. It is likely something major, and it does not sound like you will fix it yourself even if one of us guesses correctly, and there is no way to know which guess is correct.

At this point, you are correct on all accounts. Prior to my last post, I was hopeful that it WAS something that I could fix on my own. But seeing that everything turns as it should up until it connects to internal parts, has led me to agree with you that a shop will need to diagnose it.

[Opie55]

Originally Posted by 16Alpina

At this point, you are correct on all accounts. Prior to my last post, I was hopeful that it WAS something that I could fix on my own. But seeing that everything turns as it should up until it connects to internal parts, has led me to agree with you that a shop will need to diagnose it.

Any verdict?

[bagged650.xi]

Since you said you bought it certified from Bmw dealership you should check to see if they applied an extended warranty aswell since it’s certified, I had purchased certified cars that had come with 2 to 4 years of extended warranty and was not aware till I took to the bmw dealership for issues to later find out it had warranty being certified ore owned . Good luck

[16Alpina]

Wow, didn't realize it has almost been a year since this happened! I do have an update though, for those who may be experiencing the same thing. As soon as I removed the propshaft so that I could remove the rear diff, I discovered that I had stripped the teeth out of the prop shaft rear flange, where it connects to the rear diff. It is a triple winged flange that is toothed on the inside and slides over the toothed end of the pinion. The flange is pressed steel and is apparently known for being weak. I purchased a billet steel machined one from overseas and was back up and running within days after its arrival.

[kinglambert24]

Originally Posted by 16Alpina

Wow, didn't realize it has almost been a year since this happened! I do have an update though, for those who may be experiencing the same thing. As soon as I removed the propshaft so that I could remove the rear diff, I discovered that I had stripped the teeth out of the prop shaft rear flange, where it connects to the rear diff. It is a triple winged flange that is toothed on the inside and slides over the toothed end of the pinion. The flange is pressed steel and is apparently known for being weak. I purchased a billet steel machined one from overseas and was back up and running within days after its arrival.

Got a link to the upgraded flange ? Think im going through the same with my car

[SFGent]

I just went through the same exact scenario you went through with my 16 B6. It's sitting at the shop now, will hear back soon on what they say.