because the transmission is going out, it need rebuilt or replaced
If it has an automatic transmission, it probably needs to be replaced or rebuilt.
I had the same problem in my 95 Lincoln continental and it was solved instantly by replacing the transmission mounts. I haven't had a problem since.
the clutch or clutches in the transmission are bad,even if changing the tranny filter helps the forward gears will not be right and quit again
Transmission fluid.
A transmission that causes the RPMs to increase without changing gears could be in need of fluid. If that does not fix the problem, it may be the car needs a new transmission. For safety reasons, it is imperative the car is taken to a trained mechanic to be diagnosed properly.
Your transmission is in need of servicing.
Your going to have to get your transmission rebuilt or get another put in.
Your transmission will slip and clunk or bang when changing gears, can have trouble changing thru the rand of gears, ans will eventually over heat and burn out.
Broken motor mount
Your gears is stripped and you need a new one or that one rebuilt!!
I would try changing the transmission filter and transmission oil... It problem is still there you may have to get your transmission rebuilt.