I've got a 2003 Ford Explorer NBX with a 4.6L V8. I get a clunk when shifting from 2nd-3rd or 3rd-4th, or when downshifting between the same gears. The clunk is rarely consistent and sometimes violent. Of course, the violent shifts haven't occurred when I've taken it on a test drive with a dealer's service manager. I've been told by dealers that the less violent clunks are "normal"; that some slack in the hydraulic transmission or between the transmission and the rear end is normal and will cause the clunk. The same or very similar problem was once fixed by repairing a broken transmission mount, but I've been assured recently that all mounts are OK.

Slow, steady accelerations tend to cause the violent shifts between 35-40MPH. If I start from a dead stop and just push the gas pedal to the floor, my Explorer doesn't accelerate smoothly at first, and I'm suspicious of the automatic 4 wheel drive mode in that circumstance, which makes me think the clunk I've described above might not be a transmission problem, but a front wheel transfer case problem. I'm not sure.

My warranty is almost up, and I need to know what the future holds for this vehicle. Any similar experiences, or advice on getting to a root cause?

 

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