This is a very general and vague question. What do you mean by slow? Does it feel like there is something inhibiting it, like having the parking brake on? Does the engine sputter or knock? What other symptoms does the car have?
if its a rear wheel drive its possibly a U joint if its a front wheel drive transmission fluid is low or its just time for a new transmission or a rebuild on current transmission. rebuilding a transmission is often better because you already know the car you have verses buying a different car you know nothing about.
Are you asking the cause of the leak or cause of the not moving problem. If your fluid is low that may be the problem right there. YOU CAN BURN OUT A TRANSMISSION BY NOT KEEPING FLUID FULL!!!
There can be several things that will an automatic transmission not to work properly. The most common cause is a lack of transmission fluid. Broken shifting linkage can also cause the problem.
transmission is gone.
Yes, well I can do it on my car
Could be a universal joint. If front wheel drive, it could be the constant velocity joint. I am assuming you have an automatic transmission. If it is a standard transmission, it could be the throwout bearing.
No fluid bad clutches in the transmission bad or broken linkage no driveline motor not running
Transmission. Get out your checkbook.
Get new transmission
DRIVE!
bad transmission
what is the problem when the car will not go in drive or reverse? and the transmission fluid is still full