all 3.54 gears break due to how thin they are on the pinion cuz it has 13 tooth where 4.11 has less so its thicker on the pinion, mine broke and i went back with 3.54 i like being geared high and i got 33" tires just my pennys worth

 

4.56 or 4.88s and yes you do have to change front and rear...my buddy ran 4.56s with 37s on his 02 dodge and he ran highway speeds no prob with an auto trans...

 

i went with the 4.56. i talked to two shops i trust and they both said either 4.56 or 4.88. i think 4.88 would just be too much.

 

Dudes... You can buy a Ford Ranger with 4.10s and 235X16 tires. 4.10 is not that high a gear, and if anything is still way under-geared for 40s.

Check the chart that Hammer posted. I use something like that all the time myself.

4.56 would be a good compromise for street use. Off-road, even 5.13 are too tall.

With the larger diameter ring gears, going up in gearing (4.10, 4.56) doesn't create as much a problem for gear strength as it does with a much smaller ring gear (Dana 30 - front axle of a Jeep for instance). You have 2 teeth on the ring and pinion until after 5.13.

Can you even drive your truck around town in OD with 3.54 and 40" tires? Seems like it would be barely off idle at 55.