Autobox playing up on kit car

[Wheelrepairit]

Hi Folks,

Have a Sylva Striker with 1600 xflow with mk2 escort auto box, with a bit of a problem.

Sometimes, well approx 25% of the time, i put it in gear, rev away, and nothing, stays still, move gearstick about, waiting for it to go into gear.Worse when cold.

Also some times it just does not want to change up, stays in 2nd up to 6000.

Ive changed gearbox oil, dosent seem to have helped.

Any ideas folks.

Regards
Pete