You can't switch into four low when driving that fast. Truck won't let you and tranny has to be in N.

 

Correct it won't let you shift lo in the wrong conditions

 

Probably ok. If I understand correctly the shift on the fly allows shifts up to 55 mph?

I don't understand why you're such a troll. But you are. Lets see you drop ****coma into 4x4 at 55mph. Bet you wouldn't. Learn to read before you troll.

I don't believe the truck will shift into low after a certain speed. There's a thread about this somewhere....

 

Its called "Four Wheel Drive on the Fly" for a reason. You can safetly shift in 4x4 High up to 55mph (Maybe 60mph, cant exactly remember.)

 

Think you're right. 55 is the magic number.

 

My Jeep is the same way... but its a floor shift, always scares me. Im waiting for bad noises when I pull the lever.

Dont forget to not be on the gas pedal when switching though! Thats putting a load on the system and not a good idaea.

 

I used to switch into 4wd when pulling my (10,000lbs) boat out of the water. The ramps were always covered in slime of some sort or another..
Anyway, more than once I forgot about it being engaged, didn't see the dash light, and wouldn't finally notice 'til I was on the freeway doing 70mph or so and the 'humming' made me pay attention.
Of course it wasn't a Ford(2500HD), but as others have said, you're gonna be fine. Matter of fact, if you don't use your 4wd it was prolly good for it to circulate lube through everything.

 

Nah going to 4hi in a jeep is no biggie. Going to 4lo or out of it is a little bit of a scary task until you get used to it though

 

It won't hurt to shift on the fly at high speeds, I do it all the time.
Also i am a big believer that using the 4x4 more is good for it,,, it loosens and lubes the driveline system.
The guys that DO have the 4x4 driveline problems are the guys that NEVER use their 4x4

 

Tacoma I have a suggestion for you. Wait for a nice hot dry day about noon so the roads are nice and dry. Turn on four wheel drive and go for a nice long trip through the mountains to lube up your system. Report back. Unless you have full time 4x4 I'm guessing you won't like the results.