possible auto dramas

[V8falcons]

Gday fellas,this is mostly related to my auto trans but I want to pick the owners brains of AUs to get a better,AU only related answer so I wil post this here in the AU section before the transmission forum.

Ive been spending too much time on the AU sr wagon lately for my liking,with trying to fix the timming case oil leak(still not completely sorted),replaced the radiator and fitted an external trans cooler.

Now the trans seems to not be changing into top gear or overdrive on the expressway or from 80ks and it will rev at around 200-400 rpm higher( or About 2400rpm at 110ks) than our au ghia will at the same speed.
Since ive done the external tran cooler I have noticed this but cant be certain,my concern is (or one of them) would be the extrenal cooler size I fitted which now bypasses the new (manual) radiator totally.
I told the guy at the spares shop this trans will now be reliant souly on the new external cooler and he has suggested I choose this unit which,I think may be too small for the job.Its about 400 x 200 x 25mm(any one know the capacity of the radiator internal trans cooler for an AU).
After the cooler was fitted,I topped up the oil in the box but has since not changed into D-Drive from reverse a few times now for 5-10sec and no drive.

The next concern is,do the gear selector solinoids require replacing on AU box's after 250ish ks or is it worth going down the low k box route instead???
And can the higher revs(gear selection) be related to the TPS sensor as it may have been moved when LPG was recently installed????????

Any help would be appreciated,Im getting close to just considering now buying both a low Ks eng/trans and replacing the lot due to it having done 250ks now?????? Sorry for the long post : :