Ford 6.7L Power Stroke Diesel :: When Engage Low Range In The Diesel / Transmission Starts In 2nd Gear

Well, last night I took my F-350 up a wheeling trail. I'd been up quite a few times in my old Rover, so I knew I could go a ways in without damage. Just uphill, muddy, and ruts / rock steps.

One thing I notice is that when you engage low range in the diesel, the transmission starts in 2nd gear. My previous gas Super Duties always started in 1st. I'm assuming this is to protect the transfer case from torque overload. Also, the throttle response seems to change when low is engaged (the pedal becomes less responsive, which is nice).

I've had the gas Super Duties off road before, and all of mine have had the locking rear diff. The diesel lugged along perfectly. My biggest fear was crunching the DPF / SCR / DOC canister on a rock step. In that respect, I'd rather wheel a gas. The manual shift function makes a lot of sense in low range - you can force a start in 1st, 2nd, or 3rd. And prevent meaningless up / down shifts since the grade can change quickly.

These trucks' biggest hindrance is their size. However, if you have the trail room, they are actually excellent off road. Many people look at a Super Duty and see a vehicle good only for pulling or hauling. Not so, these trucks are as good as a Jeep off road, again with trail room being the only concern. The locking rear diff was never really needed, but I engaged and disengaged a few times to keep the mechanism free. I really love this feature.

One thing that happens frequently for me in north-east wheeling is water crossings. Could be a simple brook but mostly it is mud holes encountered on tight trails. In some cases these are only a foot or so deep; in other cases they are 4 feet deep. Ford states to "try" to keep the water below the level of the hubs, which amounts to about 15". Aside from possible front axle contamination, my biggest concern would be the electronics on the diesel which are mounted to the frame or floor pan (transmission module, NOx module, etc.) The gas Super Duties don't have these concerns. In the old days, as long as a diesel had air, the engine would run under water. This engine requires electronic control of many things, including the injectors...so it won't. There are also some axle / transmission breathers which run about floor pan high to be concerned about, but these can be easily extended.

Maybe it's due to the twisty frame which GM loves to insult Ford about, but these trucks have excellent wheel articulation. I'd be surprised if a coil sprung power wagon flexed more, at least in the rear. I'm impressed.

Finally, the traction control. I experimented a bit on a slippery rock step. This was the only step which required the rear locker - sort of. The front wheels climbed the step, but the back flexed to the point of one rear wheel basically almost off the ground and severely unloaded. With 4x4 Low engaged, and traction control "off" as much as Ford will allow, the truck could not pull itself up. Turning traction control on allowed the truck to very nearly pull itself up. A little more throttle / finesse probably would have gotten the truck over, but lots of ETC operation glazes the brakes and spews brake dust everywhere. Being able to start in a higher gear manually really adjusts the torque control. Locking the rear end and the loaded wheel bit right in and she went up and over.

When doing some off-road driving, the "off-road" screen for those of you with the LCD message center is kind of fun and informative to watch. It's nice to see how far your wheels are turned left or right when spinning in ruts or what crazy angle your truck is on. Howie Long could probably document the exact up / down / left / right slope angle a Super Duty needs to be on in order for the tailgate not to open. I never had an reason to open the tailgate while in these crazy angles, of course.

Overall, very impressed. It's not as good as my old Range Rover, but I would say more talented off road than ALL other Ford vehicles except the Raptor.