AU Fairmont transmission problems

[aufairmontwa]

I am hoping someone can give me some advice cause I am pretty much at my wits end!

I have a 1999 AU Fairmont 5.0L and there is an issue with regards to the transmission. When first driven from cold the car drives absolutely fine however after about 15-20mins of driving the problem starts.

Once warmed up the car seems to rev out higher in first gear and then the car jumps into another gear, which to me seems like 3rd and not 2nd gear. This only happens when going from 1st gear, all other gear changes seem ok.

I took it to my usual mechaninc and he looked at it an advised that it was actually a miss fire which was causing the issue with the transmission so I had new plugs, leads, cam shaft sensor etc.. changed to fix the miss fire. Obviously the mechanic never drove the car for any period of time as when I drove it the following day after a while the same problem was still happening.

I took the car back to the mechanic and he had advised that the problem is being caused by a faulty radiator which is leaking fluid into the transmission however he has also said that the transmission also needs replacing.

As the car drives fine when cold I am a little baffled that the transmission would need replacing however not being a mechanic I am only going on guess work?

I am interested if anyone has come across this problem or has any advice on what the problem may be, I would be greatly appreciative of suggestions.

Cheers,

Dan