Gentlemen,

2000 Expy, EB, 5.4l, automatic tranny with A4wd

I was driving down the road when suddenly there was a violent knocking under my feet and under my seat. Like a machine gun, but not as regular. I stopped, nothing to see underneath, and the noise was gone when I continued on. Until a few miles later, it started again just as suddenly.

Once started, the noise continued regardless of driving speed, although it was lessened by driving slowly. Bumps, turning, seemed to have no effect.

From the location of the noise my first thought was the Torque-On-Demand A4WD transfer case, which is located approximately under the front seats. Like it was seizing or something. I wondered if the transfer case shift solenoid was engaging. Of course, this doesn't have a solenoid, it has an electric shift motor.

So I disconnected the wire harness that goes to the electric shift motor on the outside case of the transfer case. Actually, there are two wire harnesses - one has just four wires, the other has about a dozen wires. I disconnected the one with the dozen wires as it appeared to feed into the shift motor.

Anyway - I then drove the 30 or so miles home without further incident - like it never happened. I made sure to drive at all sorts of speeds from dead slow to 55 mph. No problem.

I want to drive it some more tomorrow to see if it continues to be ok like this, but wondered - am I doing any damage to it driving with this shift motor disabled? Should I also disconnect the other wire harness?

Thanks.

 

Well, moot point, it turns out. Took it for a good drive today, with the transfer case shift motor still disconnected, and it started making the noise again. Got onto a back country road and opened the window and stuck my ear out - holy cats I never heard a front wheel bearing do that before. Shakes the whole underside of the cab - then stops - then starts again. Good news it, it's not the transfer case. Wheel bearing - easy fix.