yo,
GL with it!
With the 33x12.50xr15s on, you'll feel the need to re-program the Programmable Speedometer Odometer Module (PSOM)
(Speedo) to help it read more accurately as well as have the tranny shift better; I ASSume it is the E4OD?
Steve83 (Steve, That dirty old truck) at
http://www.supermotors.net/registry/media/76023
soon in your profile, include your year, engine, trans, Xfer case & locking hub type (auto or manual) and any major mods such as body or suspension lift, etc. or in any question post. You'll get more accurate replies
Do you have any maintenance records on it? If not, contact a dealer to see what maint was done to it a Ford dealership in the past (need VIN)
or on-line dealer service record summaries (Ford is adding entries now), etc. at myford.fordvehicles.com
Also get the maint shcedules (reg and severe duty)
If no maint records are avail; check and replace, if needed all filters and fluids.
Esp if it is an Auto tranny; fluid level; when at norm op temp; after running thru all gears & reverse; no burnt toast or whitish (water) deposits on dip stick.