Generally, one should have the codes scanned to make sure all the sensors are working correctly. Out of spec sensors can cause damage to the transmission. Make sure the alternator / battery voltage is correct too as I've had hard shifts when my alternator died. Failing that, you'll need to have a transmission shop check it out, working on external checks first before tearing it down.
It might be the transmission range selector
too low trans flid
The Mercury Villager does not have an interference engine (in spite of what you might hear) and will not be damaged if the belt breaks.
wind
Generally, Ford, Lincoln, and Mercury vehicles use Mercon ATF. For your 1993 Mercury Villager, use Mercon IV or Mercon V automatic transmission fluid. The additives in IV and V supercede any and all of the additives that are in the previous Mercon ATFs that may have previously been recommended for use in your vehicle. Hope this helps! Unsure of validity of above statements. The Mercury Villager is NOT a Ford vehicle. While it might look like a Ford Windstar, it is actually a Nissan (Quest, I believe). Mercon Transmission fluid is not suitable for most Asian cars.
This can be a tricky process. Unless you have some experience with vehicles, it might be best to leave to the professionals.
You might try this site (http://the12volt.com/) and see if it has the answers you're looking for. You have to register to enter.
The ball joints on a Villager are actually easy, just bolt on parts, the only hard part might be getting the stud separated from the knuckle, but if you're replacing them just use a wedge and it should be easy.
Your transmission might slip on your ML320 because the transmission fluid is low or because the transmission is damaged. The most common cause of transmission slip is wearing of the transmission.
The entire instrument cluster must be remove to replace lamps. If equiped with Electronic cluster, it might be better to take it to the dealer.
This switches between a "power" and "economy" mode, depending on whether you might be towing something, for example. It is normally on E.
First you should Check out your Transmission oil level that could cause your car too jerk into gear. The only other thing it might be if the transmission is going bad and you should have it checked by a transmission specialist