I've got a 2001 super-cab with a 4.6 liter, 3.08 rear end. The rated towing weight is 2000lbs. If I go up to a 3.31 I can almost triple my pulling weight. Is this very easy to do? Are there parts readily available? What kind of $ am I looking at? Any input would be appreciated.

 

Changing gears is never cheap. Figure it costing about $500 per axle. Then, just going to a 3.31 is not much of a change. Not sure where you got your "triple" figure, but that sounds a bit high....

Consider going to 3.55 or even 3.73. Most of it depends on your priorities. Each gear has it's advantages and disadvantages.....

You need to decide what your priorities are going to be. Do you tow all the time? Drive alot of highway miles? Offroad? etc.

Do you have an auto or 5-speed?

 

Biggest factor is manual or automatic. If you have manual, towing a heavy load will require you to slip clutch when starting out from dead stop--result: shorter clutch life. If you have an automatic, loads between 2K and 4K shouldn't cause a problem due to torque converter doing its thing, just don't tell Ford you did it. Frequency of towing is also important--once in awhile is ok; every weekend, you won't like it.

Considering only rear-end ratio as the controlling factor--many, many folks tow more than the factory says they can and get away with it. You sure don't want to tow more weight than you can stop, and I don't think there is any difference in stopping ability that is caused by the gear ratio being a 3.08 or a 3.31; the braking ability should be the same, unless the rotors are bigger for some of the higher tow ratings.