[humbertob]

Hi folks, as the title states, I need to disconnect the drive shaft from the rear differential on a 2009 BMW 328i sedan, I'm towing the vehicle for like 160 miles and my mechanic advice is to disconnect the drive shaft from the rear differential to haul the car, my question is: will I need to remove the complete exhaust system to acomplish this job? any advice or diy? thanks in advance folks !

[lowrydr310]

Originally Posted by humbertob

Hi folks, as the title states, I need to disconnect the drive shaft from the rear differential on a 2009 BMW 328i sedan, I'm towing the vehicle for like 160 miles and my mechanic advice is to disconnect the drive shaft from the rear differential to haul the car, my question is: will I need to remove the complete exhaust system to acomplish this job? any advice or diy? thanks in advance folks !

To remove it properly, you will need to remove the exhaust. In theory you could jsut disconnect it at the differential but then there's no reasonable way to secure the rear half of the driveshaft and keep it from flopping around. The simpler solution is to tow with a flatbed or a full trailer where all four wheels are off the ground.

[Rmtt]

Not sure how the 328 differs from the 128, but I replaced my entire differiential without having to touch the exhaust. Just a heat shield to move out of the way.

But the bigger issue is like the previous poster said, finding a way to secure it on the end. You have some play with it, but there really isn't anything like a brace in the immediate area to secure it to that I would feel safe trying.

[Efthreeoh]

So my thoughts are disconnect it at both ends. You can get to each end without pulling the exhaust. The problem will be keeping the rear of it front kissing the diff input flange. The rear flange is precision fit, so once the bolts are out, you have to pry the drive shaft flange away from the diff input flange. There's enough play in the center bearing mount to pry the flange apart, but it wants to sit just in the face of the diff flange. The front of the drive shaft is a splined accordion joint so you can effectively compress the drive shaft. Some versions have a set-bolt (set screw) to lock the accordion joint once the driveshaft is at length. You'll have to blindly find the set-bolt and loosen it. Of course you need to mark the orientation of the driveshaft to their respective flanges and properly suspend the drive shaft so it doesn't stress the center bearing.

I really don't see why you can't let the driveshaft spin with the transmission in neutral. Is the car Auto or manual?

Pulling the exhaust is not fun. The front flange bolts are probably rusted in place by now and without air impact tools, you'll just ring off the nuts. I wouldn't fuck with the exhaust. You'll also need a transmission Jack to support the exhaust; it's heavy and awkwardly weighted.

[humbertob]

Originally Posted by Efthreeoh

So my thoughts are disconnect it at both ends. You can get to each end without pulling the exhaust. The problem will be keeping the rear of it front kissing the diff input flange. The rear flange is precision fit, so once the bolts are out, you have to pry the drive shaft flange away from the diff input flange. There's enough play in the center bearing mount to pry the flange apart, but it wants to sit just in the face of the diff flange. The front of the drive shaft is a splined accordion joint so you can effectively compress the drive shaft. Some versions have a set-bolt (set screw) to lock the accordion joint once the driveshaft is at length. You'll have to blindly find the set-bolt and loosen it. Of course you need to mark the orientation of the driveshaft to their respective flanges and properly suspend the drive shaft so it doesn't stress the center bearing.

I really don't see why you can't let the driveshaft spin with the transmission in neutral. Is the car Auto or manual?

Well, I just forgot to mention, the car is equipped with auto trans !

[Efthreeoh]

Originally Posted by humbertob

Well, I just forgot to mention, the car is equipped with auto trans !

Then you need to have the trans in neutral, so that means leaving the key in the dash and disconnecting the battery.

[humbertob]

Originally Posted by Efthreeoh

Then you need to have the trans in neutral, so that means leaving the key in the dash and disconnecting the battery.

So you mean that I don't need to disconnect the drive shaft at all? just put the trans in neutral with the key in and haul the car that way for 160 miles?

[Efthreeoh]

Originally Posted by humbertob

So you mean that I don't need to disconnect the drive shaft at all? just put the trans in neutral with the key in and haul the car that way for 160 miles?

Well if it was a manual trans I'd say yes because it would just spin the trans and not hurt anything. An automatic is a different story, it most likely would heat up the oil without being able to cool it. You shouldn't tow it more than 20 to 40 miles that way. So with an auto, you'll need to disconnect the drive shaft.

[dpaul]

Yes, most automatic transmission have the fluid pump driven by the input shaft. So if the engine isn't running, there is no direct lubrication. Probably OK for short tow but 160 miles is asking for trouble.