New to me is a 97 fSD truck with an auto tranny. It seems the prevailing wisdom is to avoid use of overdrive while towing, hauling etc. I had about 3 ton on this truck today so I took it out of od. But, since it has 5.13 gears in it it is very slow on the highway, like 45 mph at 2500 rpm.

My question is about the use of od in this situation. Is the od a weak link or do problems arise from the trans having to shift all the time when weighted down? it seems with these gears and a powerstroke that the truck can easily pull in od without having to downshift much.

I am having fun with my new ride but I don't want to kill the transmission. I am used to towing with my f250 in od all the time (6 speed manual).

 

No, it's not a weak gear. Your "prevailing wisdom" is wrong. As long as it isn't frequently shifting out of overdrive you can tow in overdrive.

 

Yes the "shifting" kills the overdrive but direct gear is always the strongest gear in any transmission. Lugging an engine in overdrive while towing can burn more fuel than towing in direct drive.

 

With your 5.13 gearing use your overdrive, however if the tranny is shifting back and forth then lock out OD. I usually hit the OD button just as I hit the hills then use OD once I am back to level cruising speed.