download this manual . It has your automatic information in full detail
so you know what you are looking at .
second gen is also verada
downloadable manual
http://www.lisho.net/?page_id=3 have your auto serviced and supply only mitsubishi oil suited to your gearbox
the wrong oil may be in your box causing this problem (oil should be RED)
You need someone to diagnose the electrical funtions of the box
any good auto shop should be able to do thison the outside of the box are two electrical devices... A and B pulse generators
related to the brake band ...if faulty the sensors may need to be replaced
diagnostic fault 31&32
4th gear slip
the overdrive may need the overdrive friction discs replaced
box doesnt have to come out (easy fix.....called an end clutch kit)
the kick down band locks on to a drum so the gears can change
the kick down band can be adjusted for smooth changes
the two auto places from your description are keen "" to rebuild your box""
when it may not be required