Mentor 2004 Autogearbox

[GS25]

Hi all . I bought a Mentor 2004 with an automatic gearbox.
There is a weird accurance when the gearbox changes from 3 to 4 or visa versa.

It is easier to explain when the gearbox changes from 4 to 3 .
Travelling at 80 km/h (+/- 50mph ) , if I slightly press down on the accelerator pedal the gearbox changes up , the revs rise by +/- 500rpm if I press more on the accelerator the gearbox changes up again and the revs go up by another 500rpm . Are you with me up to here . From 4 to 3 the gearbox changed twice .

However if I am travelling at 80km/h and press the OD button and disengage the overdrive the gearbox changes up to 3 and the revs go up by +-/ 1000rpm.The gearbox only change once .

This gear change from 4 to 3 does not interfere with the performence of the car , it is however annoying , if I take my foot totally off the accelerator pedal and then press it again ever so slightly the gearboxs changes up , revs go up by 500 rpm , for an instant and then it changes back down again , revs drop by 500 rpm .

What does affect the performence of the car is when the gearbox changes from 3 to 4 .It changes " most " of the time twice , each time the revs drop by 500 rpm , however on occations it change from 3 to 4 in one gear change and the revs drop by 1000 rpm .When changing from 3 to 4 the gear change is not immediate , the revs linger at +-/ 3000 rpm for 1 second or even 2When overtaking and the gear changes from 3 to 4 it is very scary form the gearbox seems to linger ..... before engaging 4th.

My question 1. Has anyone had a similier experience with a Kia automatic gearbox . How was it repaired ( my garage is clueless bless their souls ).
2. Does this gearbox have what is called a half gear between 3 and 4 gear , e.g: 3 3.5 4

Help the garages are hopeless .........