2001 F-350 2WD 7.3 auto

I'm towing about 10,000 lbs in a car trailer. Should I always be towing in the "drive" selection on the transmission? Or should I use the overdrive? I am pullling on a lot of 4 lanes with some hills. A couple of guys told me to let it in the drive
mode, but the engine is turning about 2500 rpms at 70 mph. What do you recommend? Thanks for the info.

 

I tow the same weight pretty ofen and I run overdrive most the time on winding mountain two lane roads mostly drive
I normally let truck decide

 

As long as it is not "hunting" (swapping in and out of OD) let the truck decide

 

FWIW I towed my race car last weekend to Maryland and back for the first time with my new/used F350 PSD and I let the truck decide and it ran great.

I was just amazed at the difference in towing verses the 93 F250 (gasser) I had it was totally night and day.

About a month ago I put on gauges from Diesel Manor and the EGTs were fine and the highest the tranny temp got was 150 degrees.

I wasn't towing 10,000 pounds, it was an 18 foot open trailer and 3500 pound race car.

After towing with my diesel I will never buy a gas truck again......lol.

 

You select the "drive = D" position with the manual shift lever for both 3rd and 4th (OD) gears, and then select between 3rd and 4th using the OD lock out button. What is your diff ratio (4.10 or 3.73 ?) because with the TC clutch locked up (which it should be), 70 mph at 2500 RPM doesn't match either diff ratio for 3rd or 4th gears? If you have stock tires, 70 mph is either 2169 RPM in 4th or 3052 in 3rd with a 4.10 or it's 1972 RPM in 4th or 2776 RPM in 3rd with a 3.73.

I'm guessing you have a 3.73, and your choice for 70 mph is either 4th at 1972 RPM or 3rd at 2776 RPM. If you're running a stock PCM, and try to pull much more than a 1% or 2% grade, the PCM will unlock the TC clutch, shift down to 3rd, and relock the TC clutch, and if you let this happen under load (your foot still pushing on the throttle) this shifting maneuver scuffs the tranny clutches, builds heat, and places unnecessary wear on the tranny which shortens its life. You can see the hill (and its steepness) from a distance, whereas the PCM can't, so the PCM won't shift until you're already part way up and discovers the engine can't develop enough torque, and initiates the "torque demand " downshift that I described above.

It's much easier on he tranny if you initiate the down shift just before the PCM does, by letting up on the throttle and pushing the OD lock up button, and then easing back onto the throttle after the TC clutch has locked up again. If your interested in a method for shifting that minimizes the wear on your tranny, check out this thread https://www.ford-trucks.com/forums/615365-tc-lock-unleash-the-psd.html and especially read all of my posts on it concerning the way I shift the tranny while towing. To shift this way, you'll need to install a switch to allow you to manually lock your TC clutch.

 

did you check your mpg? and what was the difference from the gasser to the psd?