2003 Ford Escape problem

I'd have to drive the car and work the steering wheel and brakes to get an idea of what's happening. You might want to have someone at the repair shop go for a drive with you so you can show them what it's doing. I can think of a few possible causes, but all of them should have been noticed during the previous service.

I don't like that stuff because if you get a nail in the tire now, it is very difficult to patch it or insert a plug. Those won't stick to the rubber tire once it has been coated with any type of chemical. As for it settling to the bottom and freezing, it depends on what that chemical is supposed to do. It normally coats the tire as soon as you start driving. If it were expected to run to a leak, it would have to not freeze to do that, and it would be formulated to freeze at a much lower temperature than water freezes at. If it coats the tire, then stays there, it already did that before the crash. If it could settle after that, you'd hear all kinds of stories about out-of-balance tires from many unhappy people.

This kind of sounds like a half shaft problem in some ways. The clinker with the Fix-A-Flat stuff is if the mechanic's suspicion is true, you will have no unusual noise or clunking, no vibration at low speeds, and the out-of-balance WILL show up as a balance problem at higher speeds. The steering wheel is where you'll feel it too, besides in the seat and floor. Balance problems don't cause any symptoms at low speeds. If you see the steering wheel oscillate back and forth at low speeds, as in when driving through a parking lot, that is caused by a broken belt in a tire.

You need an impartial person to listen to the noise and test-drive the car. The best place to go is to a tire and alignment shop. Many of them don't charge for a quick diagnosis if it doesn't take real long. The people there are experts at finding the causes of noises, vibrations, and bad tire wear.

The only thing I can think of that might occur consistently at that speed is the torque converter is locking up and you're feeling it. The torque converter is a giant donut filled with transmission fluid that is spun by a fan hooked to the engine, and that spinning fluid spins another fan hooked to the transmission. The slippage is what allows the engine to stay running while the vehicle isn't moving but it's in gear. That slippage also results in a loss of fuel mileage. Chrysler developed a way to mechanically lock the torque converter to improve fuel mileage in the mid '70s. Now everyone uses it. For that to occur, the transmission must be in third or fourth gear, the engine has to be warmed up, and the vehicle has to be above a specific speed, typically between 35 to 45 mph.

Sometimes using the wrong transmission fluid will allow the lock-up clutch mechanism to chatter a little as it engages. You can get a shudder or vibration too for one or two seconds. That doesn't really hurt anything, but it can be annoying.

To tell if this is what you're feeling, drive at highway speed with the engine warmed up, hold the accelerator perfectly steady, then tap the brake pedal with your left foot. That will make the torque converter unlock, (in preparation for coming to a stop), then it will relock again in one or two seconds. If you feel a shudder each time you do that, it's the torque converter. You'll hear and feel the engine speed up a little at the same time, then slow down a little.