symptoms..
1.Loss of drive at junctions or turning slow corners
2. intermittent low speed reving with no drive until gear selector moved.
3. What appears to be torque converter/gear slippage from low speed especially cornering. (accelerating out of a slow corner)
4. intermittent rolling backwards when stopping/pulling up at lights on a hill.
5. stiff gear lever

Just spray good old WD40 or 3 in 1 oil over the linkage assembly (opposite side to fill/level plug) and move the selector through P N D R several times then drive 3 miles and repeat process. You can buy and fit new parts but removing corrosion and lubing can easily be done with WD40.



Under the car, drivers side in-line with front of cubby box.
In between the gearbox sump and the catalytic converter you will see the link / sliding rod on the side of the gearbox which links the the gear selector knob with the gearbox as in photo.

Click image to enlarge