My truck is an F150 extended cab, 302 with e4od and 3:55 gears. Pulling about a 4000 pound trailer up a long 8% grade the trans shifted out of OD then slowed to about 32 MPH. It then shifted down to second and the speed climbed back up to about 40 as I reached the point where the hill leveled off and it shifted back to 3rd then OD. Sense I don't have a tach, I am wondering if I should manualy pull it down into 2nd gear instead of letting the motor lug down that far?
Thanks, Jerry

 

You should manually disengage OD as you begin to climb a long hill like that but then let the transmission do it's thing. Also if the transmission continuously hunts between D and OD when towing then you should permanently disengage OD and adjust speed accordingly.

 

I'd say the same thing if you're on a steep enough hill that it's hunting between 2nd and drive, then shift it manually to 2nd until things flatten out enough that it'll pull the next gear. But if it's happy to stay in drive I'd leave it there.