engine sounds forced

[baff2004]

When traveling at highway speeds the engine sounds really forced. Im not sure if it was the big tires that had that effect on it. It sounds like the transmission doesn't want to shift in to 4th. When kept at about 70mph shifts between 3rd and 4th gear depending on the incline or decline. But I know the car could pull itself on the incline in 4th gear. How can i change these settings? Or at how many rpms do i want the tranny to shift at?
Also my gas mileage is really crumby. Like 230 + or - miles a tank. A towing fan was put in by the previous owner. If i change the fan will I see a good improvement? (the fan is the only thing you can hear, my buds say it sounds like an airplane)

 

[Majisto]

What is a towing fan? If that fan is large, it could be straining the motor trying to be turned.

 

[Jason_25]

It sounds like the fan clutch is bad and causing the fan to turn at engine speed. That would explain the low mileage and poor performance.

 

[Billy177]

did you correct your speedo for the 33's if you did than an apten can fix all that. gears will also help depending on what you have now

 

[baff2004]

fan clutch

I think it is the fan clutch. Is the fan supposed to turn at engine speed? Also the temp gauge stays really low. The previous owner said it was because of the towing fan. I think the clutch is bad, but Im not sure? How can I be sure?