Rough idle can often be attributed to a vacuum leak. I would inspect the lines and check under the vehicle for any unattached hoses (or hose nipples) Perhaps all the vacuum lines werent connected or a hose cut inadvertently. Hope this helps.
This is far beyond anything that WikiAnswers can answer. This answer could take a website by itself.
When repairing a car it is important to know the costs of the repairs. To rebuild a 2500 Dodge Transmission it could cost between $2000 and $4000.
your transmission could be stuck between gears. you probably need to rebuild or replace the transmission.
The DeVille could have low transmission. Or the internal transmission bands or valves could have failed. The transmission will most likely need a rebuild.
The transmission valve body is INSIDE the transmission and generally requires a complete rebuild. If the fluid is black and smells burned, your clutches have been slipping, in which case the transmission is pretty much done anyway so either replace or rebuild the transmission or get another car.
a vibrating transmission could be caused by a bad transmission mount. If the mount breaks then the transmission will physically move causing it to vibrate.
The loud hum could be caused by some of the teeth going out on the transmission or that the transmission is failing.
It's probably the transmission, either the valve body or the clutch pack. Either way, it means a rebuild of the transmission.
Could be a frozen clutch pack. Time for a transmission rebuild.
It could mean that you need Transmission Fluid.
Worn or damaged internal clutch or transmission valve body. Either case requires a rebuild. Possible that it could be misaligned gearshift linkage, depending on the vehicle, but don't count on it.
If the transmission has electronic controls, then a module could be bad. If not, then the transmission could need a rebuild. If it is a front wheel drive, check the cv joints for damage.