durango rear end options

[oo4playmrright]

hi, my uncle has a 98 durango with the v8(not sure the size), but when it is on the highway it looks like it needs another gear. when it's running 55-60 in 4th(overdrive), it's running 2,000 rpm, and it redlines around 4,500 rpm. most automatics i've seen, with v8s run alot lower rpms than that on the highway. this might be a little exagerrated, but it's pretty close from what i remember. does anyone know a way to lower the rpm's on the highway(it's killing him in gas)? i was curious if there were rear-end options available, because it's 0-60 is impressive for a suv, maybe that's a "sports" package. if there is a rear end option, does anyone have the ratios? or are dakota's compatible? ratios for that?

or if anyone has any feasible ways to get better gas milage on the highway

[BleedDodge]

I thought it should run about 1750 in overdrive at 60 mph. Maybe the torque converter isn't locking up or something.

[oo4playmrright]

how do you check that? how to fix? replace? well i'll check his haynes manual, anymore help is welcome, thanks