I drive a 2004 F150XLT, 4wd, auto trans, electronic 4wd.

Sometimes on a hot day, after the truck has been parked for hours, I'll be driving along, 30-40 miles an hr, and the truck will start shaking, like a front end vibration. I've checked the lugnuts, the tires are balanced, letting off the gas doesn't change the vibration, slipping the trans into neutral doesn't stop it either.

When I apply the brake, the shaking is more pronounced, and when I release, it returns to the previous level of shaking.

I pull over and stop, and when I take off again, the problem has cleared.

The last time it happened, I switched to 4wd. It took a couple of minutes before I could get it back to 2wd.

I suspect a faulty 4wd solenoid or similar problem.

The dealer (Lakewood Ford, Lakewood CO) can't find any problem. You know the drill- when the mechanic test drives the truck, it drives just fine.

Does anyone have any ideas? Anyone heard of this problem before?

All replies are welcome.
Thanks,
Barry