Trouble moving in 4wd

You know, I honestly wish I could give you a solid answer to this, but living on an island like where I’m at, I can honestly say I haven’t even gotten to 60mph in a while. My average speed daily is 30mph, maybe 45mph being my top speed. It doesn’t help that my daily commute to work is only 3 miles round trip, so I make it into 4th gear for less than a minute and then I’m done. If I can remember correctly the last time I was in 5th gear, at 60mph I was probably turning no more than 2300rpm, plus or minus 100 on flat ground. Going uphill with a slight 3-4% grade, I’d probably be turning closer to 27-2800rpm and I’d still have room to give it more gas and go a little faster. Never had the feeling that I’d have to downshift for any reason going uphill. Before I came to 285s, I was running true 33s and my rpm seemed about the same driving wise. Original owner planned on running 35s with this truck but never got around to it. He was hesitant on running 35s with the 4 banger as his daily driver.

 

Everything has to match as they are all linked together otherwise the one with the higher ratio will try to drive the other faster. Tire size mismatch will have the same effect.

 

I would use the 'ol lift the truck and spin the wheel 2 revs and count the drive shaft revs to convince myself the ratios of the front and rear diffs match..... scenario sounds a lot like using 4wd on dry pavement and trying to pull a U turn..... which i'd expect a mismatched gear ratio to feel like as well..... or maybe broken teeth on ring/pinion.
Good luck and hope you figure it out...

 

You definitely would know about a missing tooth.