Hey, Bill.

I wouldn't think wheel bearings in this case. I just drove it to the store and wonder if it's the driveshaft output flange scraping. I shimmed it down about 1/4-3/8" (3x m8 washers) and had no real change. If it's the flange, it will need to be sleeved by a transmission shop.

For wheel bearings on this year of 740, I expect "sealed" hubs that are separate from the rotors and have a torque-to-yield (one use) hub nut. I added one of the diagrams for the FAQ on this model's hubs when I had the 2-piece internal race separate. The bearings are captive, but not really sealed. You can't remove them to look for signs of heat or wear, and you can't really see inside.

To check them, you really end up having to try driving at a fixed speed (30-50mph) on a curve to load each front hub with weight, then listening for a low thrumming noise that usually has rapid "beats" to it. It gets quieter and louder and quieter and louder as you drive with extra weight on it.

The only stationary way I finally found to test them was to put the hub in the air, remove the wheel, and use a hub wrench to spin the wheel by putting the hex wrench on the stud with no nut. I got it up to maybe 100rpm like that, removed the wrench, and could hear a definite thumping with every rotation that was not audible any other way. That was in like 2006, so a bit hard to recall the symptoms.


I'm going to spend the afternoon doing my girlfriend's spark plugs on a v6 fwd/awd lexus rx350, but I will try shimming the bearing up later. If it's the output flange, that might do it :)


Cheers,
Will