I do get a mild vibration at idle. I always figured it was part of the V8 experience. Maybe I should do them just to be safe. I'll look through my stack of receipts and see if they've been done before.

The question I am asking myself now is do I just drop a bunch of coin on driveline parts and get it done, or do I replace a single part at a time to try to isolate the problem.

My thought is that the truck has 140k miles, it's better to be safe and refresh the driveline regardless.

I'm getting ahead of myself, going to start by disassembling and analyze from there.

If your truck has 140K on it, I can guarantee the motor mounts are done. Im doing mine at 80K just to be safe. I believe that you will feel a significant difference when they're done. Good luck.

i am subscribed to this! about to do a very similar project as my driveline is loose as a mofo!

It can get VERY expensive to just start throwing parts at an X5 unless you're sure they are bad. A pair of motor mounts are about $225 for just the parts. On my car, the failed mounts caused the passenger side mounting bracket to get damaged, and that was a huge PITA to change. So it's not something to ignore. But they are oil filled, so take a close look at them and see if there's oil all around them. If you have near 100K miles, it's not all that unlikely they are bad.

Do keep in mind that when you pull the reinforcement plate to change the motor mounts, the bolts/nuts are one time use.

That is exactly the same simptoms i had. When my Indy told me that is caused by the rear drive shaft I thought I knew better because most of the people here did the front drive haft and the chain. So, I did as I mentioned earlier the front shaft thinking the same as you do and then the chain. I spent a few hundred on the shaft and a hundred on the chain and the final option was the rear drive shaft. The splines on the front shaft were worn out but the noise didn't go away after replacing the drive shaft and even later with a good transfer case with perfect splines and new chain. I put my money on the rear drive shaft.
You can check the front splines easily. It shouldn't take you more than 15-30 minutes. Unfortunately I don't know a way to test the rear driveshaft. Although I replaced the faulty component wasn't obvious it had a play. You need quite a bit of force to generate that clunk noise.

If you want to rebuild the TC you can find all the parts you need and it is very easy to do it while it's out. I used cobratransmission.com
The play you find can be combined from all the components in the drive line but in mine it went away by replacing the rear shaft. I also had play in the axels and getting new axels didn't do much...

Thank you. I'm going to start by inspecting the front splines. Do you have any ideas to test the rear shaft? Based on my research, the rear is not rebuildable, so just buy OEM if I want to replace?

Re: motor mounts. Truck wash under warranty til 100k so I thought they had been done at some point. Method to test if they are bad?

Yea park perpendicular against curb. Front wheels against curb. Put car in drive. Left foot on brake, hard. Right foot quick solid jab on throttle. Don't be afraid to really push it. Won't go anywhere as long as you on brakes. Do same in reverse. Have hood open and look at engine. It will come out significantly if it's the mounts. Mine went at 75k miles. Oh and they are $80 from Craig at Bloomfield BMW.

You should be able to test your whole driveline with this method. Just don't know who wants to lay under your car while you rev it.

Thanks!!!!! :thumbup:

Speaking of drivetrain clunk, one thing that CAN do this is a failed intermediate driveshaft bearing; if the rubber ring around it it totally shot.

I think one thing that would be highly useful at this point would be to get the car on a lift, and have a good independent BMW mechanic give it a total once over. If you start by replacing items that are visibly shot, you might solve your problem. And even if you don't, there's not much harm in replacing a component that is compromised...and you will narrow your search. With a lot of drivetrain issues, you can SEE the damage; ie a torn guibo. You can yank on and twist driveshafts and axles, and sometimes you'll feel play right off. The motor mounts are a bit tougher to get a close look at, but with a boroscope, you can get a great look at them from above, (and a good shop should have one of these cool tools.) Not to mention, a good BMW tech will probably be able to tell whether the motor mounts are bad just by looking at how the engine is sitting; it will often be at the wrong angle and too low.

Pay the shop for an hour's time for a full underbody inspection. Once you know the issues and associated costs, you can then decide what you want to tackle yourself vs. letting the shop handle.