F-350 transmission questions

[MOAK]

It’s amazing; I’ve spent the last couple of months, on and off, trying to find an answer to a simple question. I have the 10R100 transmission. When in 4L I can only manually shift it to either 1st or 2nd gear. It will automatically shift up to 7th gear, however it will upshift only by getting the rpm’s up to around 2500, which is ridiculous because there is 400ft lbs of torque at 1600 rpm’s. My questions are- why can’t I manually shift any higher than 2nd gear? Is it supposed to work this way? If so, I’ll learn to live with it, but it seems counter productive to have to come to a full stop on the trail before and after crawling through or over an obstacle. Any ideas?

 

[MidOH]

Yes. Switch back to 4hi.

4 low is only useful in 1st and 2nd gears. For crawling. If you're tempted to go to 3rd, switch back to 4hi and 1st or second gear.

The truck is trying, desperately, to keep you from destroying it. All that power, through the 4 low gear reduction, is bad mojo.

 

[MidOH]

I switch to neutral, while rolling, to get in and out of 4L. 3mph maybe.

After crawling over an obstacle, I crawl along for a lil while.

Same for my Ram. But the Ram has no manual mode. You have to use the lockout.

 

[MOAK]

Yes. Switch back to 4hi.

4 low is only useful in 1st and 2nd gears. For crawling. If you're tempted to go to 3rd, switch back to 4hi and 1st or second gear.

The truck is trying, desperately, to keep you from destroying it. All that power, through the 4 low gear reduction, is bad mojo.

I’m not following, as I am somewhat dim witted when it comes to modern vehicles. The truck will not allow me to idle in 4th or 5th because it thinks I’m dumb enough to let the engine bog down instead of knowing enough to downshift? But it will allow me to manually be in an unhealthy high gear in 4H. Am I thinking backwards? I don’t understand the problem with 400lbs of torque at 1600 RPMs in any gear. Wow- automatics for dummies 101- I’ll get used to it. With the old stuff we would travel all day long in 4L.

 

[MidOH]

Because that's, at least, 1088 pounds of torque coming out of xfer case. More likely around 1500 with the torque converter. Way more than enough to snap things.


Why do you need 3rd gear in 4 low?

I didn't have an opportunity to duplicate this today with my 17. The truck might just be confused.

If it really is locking out thr high gears, it's most likely to protect the chain in the xfer case. Nailing a pot hole at 30mph could send thousands of pounds of force into the driveline, and the drive line won't give since its in low. In high it would likely just smooth that hit, with the torque converter.