Overdrive Off

[MULESKINNER9]

Just purchased a 1996 f350 and LOVE it. Just have a few qeustions. I bought this truck with the purpose of towing. The trailer is 7000 + lbs. loaded. When I run it with the over drive off it stays in High RPMS and I get like 7 miles to the gal. If I run it with the over drive off it keeps the RPMS low and I get much better fuel milage. So whats the right way to maintain the life of the truck OD off and get a second job for the fuel or OD on and enjoy my truck? I have read in the manual and it does not give a diffenite either way just OD off when in steep areas.

[Wren]

If you're doing lots of starts and stops and driving in hilly areas, then use the tow/haul feature (OD off). That changes the shifting habits of the tranny.

If you're doing long hauls through flat land, then click your OD on and see if the tranny is shifting often to maintain speed. If not, then cruise with OD on / TH off. In the hills or city driving, drive with OD off (TH on).

Hope this is clearer than mud.

[SmokeyWren]

What that other Wren said.

With a 7,000-pound trailer, you normally use both overdrive and cruise control. There are exceptions:

1] When comin' down the mountain, kill the OD until you get back to the flats. Basic rule is to go down the mountain in the same gear you used to climb the mountain.

2] When in hilly terrain that causes the tranny to constantly shift into and out of overdrive, then kill the OD until you get out of the hills. That's not "hunting", but constant shifting will heat up the tranny.

The rest is personal preference. For example, when I see a grade coming that I know will cause a downshift, I kill the cruise then kill the OD, then attain the speed I plan to use to climb the grade, then reset the cruise at that new speed.

If your truck seems to downshift for every little bump in the road, you need a few more horses under the hood. But you can't add horses until you have gauges. So install at least a pyrometer and a tranny temp gauge, then install a hot-rod tune for towing. Probably the 60-tow tune from DP TUNER

With gauges and the 60-tow tune, if you have to back out of the go pedal when climbing mountains so you don't exceed 1,250º pre-turbo exhaust gas temp (EGT), then you need improvements in intake and exhaust. For about $200 you can greatly improve the intake with a Ford Severe Duty Air Induction system (AIS). For less than $200 you can replace the stock muffler with a Walker BTM #21470.

Never allow your tranny temp to exceed about 225º (with the sender in the pressure port on the side of your E40D tranny). If you ever see over about 210º, then you need increased tranny cooling, and I'd change to synthetic ATF.

[Mark Kovalsky]

Originally Posted by Wren

If you're doing lots of starts and stops and driving in hilly areas, then use the tow/haul feature (OD off). That changes the shifting habits of the tranny.

There is no tow/haul function on a '96. That's only on the '03 and newer trucks. The '02 and older had OD OFF, which is VERY different.

Tow/haul changes the shift patterns of the trans. OD OFF only prevents the trans from shifting to 4th gear. That's about the only change.

As the others have said, if you truck will go to 4th gear (which is overdrive) and stay there you can tow with overdrive on. If it is frequently shifting in and out of overdrive, turn off the overdrive.