I need to change the transmission fluid in my 89' power ram and advance auto parts recommands valvoline max life Dextron III/Mercon ATF. Is that ok to use?? or what should I use? They also have one that stops leaks which I have too.

 

The Dexron/Mercon is OK. Would avoid the stop leak stuff,works by softening/swelling the seals. Also softens/swells the lip seals in the clutch packs. Not always good. Bet you have a leak around the shifter shaft right? While you have the pan off would be a good time to drop the valve body,an' replace the seal. Digging the seal out from the top is a pain in the ***. If the shaft is sloppy,the new seal won't last long. Replace mine about every 6-8 mos. or it leaks like hell. Need a new V/B asmy transis 40 yrs old.