My truck - 2012 F150 XLT Reg cab 8' box 5.0L
My issue - Decided to try out the 4wd low today because I hadn't yet tried it in the 18,000 kms I've put on it. The road was icy anyway, so I stopped and switched it into 4 low for fun. It will not shift gears until it is revving about 4000 rpm - just screaming. In Manual, it will shift whenever I push the buttons, but in Drive, it wants to be 4000rpm before it shifts.
Any insight? My '98 in low would shift at slightly higher rpms than normal but that's expected. 4 grand seems excessive.
Thanks

 

Unless your going slow you really shouldn't use 4low, it's not for highway speeds. I would say its only good for creeping around or pulling people out from somewhere. I can't answer your question, iv used 4 low a few times but never got past like 2500 Rpms in first.

 

Thanks. I'm aware that 4 low is only for very low speed operations. I just noticed as i was creeping around that it should shift into second and didn't. That's when I decided to push a little further and see when it would. I've used my other trucks in low and they use first and second respectively at reasonable rpms.

 

Your other truck would have been a 4 speed automatic, where 1st gear in the trans is 2.84:1 so it takes longer to wind up the motor. Your new truck has a 6 speed, where 1st gear is 4.17:1, so this is why in 4LO the engine is revving to 4k. This is due to gear reduction. There is nothing wrong with your truck, its all in the gearing.

 

When I took delivery of my new FX4 the sales guy was going over everything and mentioned that in 4 low you will DEFINITELY want to use manual shift.