bro, the auto transmission is rarely a problem, unless you havent got the fluid change since day one you own the car....

the most common problem and issues I always pressed on waja car auto is the auto tranny ecu, which is located below the under the aircond.

Its a design flaw and the condensation from the air cond blower will drip some water into the tranny ecu.

I got this in after around 4 years using the car... I did confronted the proton guys for the design flaw, but they just wont take responsibilites, how ever, i did notice changes of the placement for the tranny ecu after 2005 model.....

if u change the gear box , if the ecu is at fault, your problem will still not solve...

how you know the ecu is not working... well.. when you are in D, the shifting gear which suppose to goes from 1 - 2- 3- 4 maybe now is 1 -2 -3 and never goes to 4, or goes to 4 when it feel happy ... hahah

I've never change the transmission oil from the 1st day i bought it ..so that was my biggest mistake... i just changed it 2 weeks ago...it was better but the problem is still there... i'll check on the condensation thing ...
it changes to 4th gear when car is warm .... but the problem is i have to warm up my car for 15 to 25 mins....that's really long... sometimes, i give up and drive to work... my problem is not like others, warming their cars for 5 mins only...