'09 Escudo Auto issues: can u Help??

[NuSkewdy]

I have a just bought a '90 Escudo with 16A and 3 speed auto. When cold, it changes into 2nd ok but when into 3rd it free revs for a couple of seconds then changes into 3rd. As soon as it warms up (2 mins driving) it all of a sudden goes fine.

Could it be low oil pressure caused an oil blockage somewhere - possibly in the trans part of the radiator - is it common to block up, needing an external oil cooler? Could a flush out fix it - anyone experienced a similar issue?

Oil level is full and oil is red and clean.

I'd appreciate any help.
Si / Franklin.