Suburban 1989, with the 700R4 transmission. Has overdrive, drive position, 2nd, and 1st on the shifter. Should I be driving in the drive position around town daily, at speeds under 45 mph? Then move the automatic shifter to the overdrive position after 50 mph and above speeds? Or just shift to overdrive and stay in that position always. Just want to make my tranny last as long as I can.

 

I left my 88 in OD at all times. On hills/mountains if the torque converter unlocked and it dropped out of OD i put it in D or lower till I got over the hill. I never let it bounce back and forth between gears. I never had any problems either and I towed often.