Gear engageing

The problem i have is when you select a gear with the auotmatic transmission the motor rpm drops to idle, if you accelerate the gearbox will engage when it seems it has reached the rpm speed of the gearbox and work quite happily until it falls below this speed. This happens in high and low range. Though when in drive the gearbox works correctly, only when you want to slow the car down and you manually drop it back to first or second gear I have this fault. Is there anyone with any idea on the problem? a torque relay maybe? Any help would be greatly apprecited....

Hmm, just guessing but I'd say a bad one-way clutch inside the transmission. When the gear selector is in overdrive, does it feel like the car is in neutral until you give it gas?

Yeah, the car is basically in neutral, if your heading down a hill it will take off. But the car will be slowed slightly when left in drive, so i was hopeing the problem was a small one.