sound like transmission gone
The most common reason for a transmission not to shift properly is low transmission fluid. Make sure the transmission fluid is up to the full mark.
It sounds like the 99 Grand Prix has slippage in the reverse band, or a stopped fluid path. Changing the transmission fluid and filter could help, if not then the transmission needs to be checked by a transmission since the band is inside of it.
Well if you have checked the transmission fluid levels when its cold and warm, and they are good, then you might want to get the fluid changed and have the transmission ajusted... assuming its an automatic, if its a manual, then it might be the throwout bearing, but i dont know why the temp would affect that.
Low coolant? Cooling fan not working? Radiator not adequate for engine load? if it is a manual transmission your placing a good aMOUNT OF WORK ON THE ENGINE TO CLIMB UP AND DOWN on the mountains and not to include the transmission only suggestion is nice and slow or just upgrade your coolant system
Try changing the transmission fluid and filter
Check your transmission fluid.
I would suggest you have the transmission fluid & filter changed ASAP. See if that helps.
sounds like idling too low udjust it in front of whre linkage hooks to srew it in further
The transmission of Enlightenment ideas to Greek thought influenced the development of a national consciousness.
This is commonly caused by dirty fluid and a dirty filter. Drop the transmission pan and replace the filter and refill with new fluid.
If it is a manual transmission, then push the accelerator pedal down more when you release the clutch. If it is an automatic transmission, then you probably need to get the transmission serviced. If you think the transmission isn't the problem, then get your engine serviced. To tell which is the problem, put the car in neutral and let it idle. If it is idling on low RPMs (less than 600 for gasoline, 800 for diesel [varies with car engines and age]) then it is the engine. If it bogs down when you take off from a dead stop, then it would probably be the transmission. When a car bogs down, it puts quite a bit of unnecessary wear and tear on the engine, leading to more expensive payments. I would take your car into a mechanic shop and have them look at it. Replace air and fuel filters.