1991 500SL tranny problem

[Minx]

Hello, I have a 1991 500SL that comes with a 4 gear hydraulic auto transmission with a standard second gear start.
Under full throttle the transmission downshifts to 1st gear and stays until redline then it upshifts to 2nd and then upshifts pre-maturely again to third. It's like 2nd gear is almost skipped, it's a very swift upshift from 2nd to 3rd that the engine takes time in order to cover the missed out power/speed needed to be acheived in 2nd before upshifting to 3rd.

Also when in 1st gear and under full throttle, the engine's revving sounds louder than the actual acceleration rate of the car.

Oh and I'd like to add that occasionally the gears won't change when shifting from D to 3,2,B. unless shifted back and forth again from D to B (which is 1st gear).

What can I do to fix this problem?

[Minx]

any ideas?

[per]

Have you tried to change the oil and filter?

[Minx]

Am thinking of a full tranny service