I have a question for anyone that has/is running 33" BFG M/T's (255X85X16) or is knowledge in the area of tires and gear ratios. Will the Tundra's Stock 390 gears suffice operating in fairly deep mud or wet snow conditions running the 33" M/T's or would it be best to regear to either a 430 or 456? I have a friend that says regearing will maintain the same on-road characteristics I now have and when operating in fairly bad off-road conditions the lower gearing will greatly assist my transmission longevity by not having it work so hard. The 255 tire is actually a tad smaller than the current stock tire and is only 2.6 inches wider in overall diameter so I would think the V-8, even though its a 4.7L, should be able to handle these tires with ease in all conditions.

A 255/85R16 is about a 33x10" tire. The stock tires are probably the 265/70/R16's, which is like 31x10.5". The difference between a 31 and a 33 is about 6.45%. 4.10 gears are 5.13% lower than 3.90, and 4.30's are about 10.3% lower, so the 4.10's would be the closest match.

However I doubt you'll notice all that much difference, especially w/ the V8. You will slightly lose some acceleration, and your speedo and odo will be a tad off... but as you say, the V8 should be able to handle it just fine. Think of it like you're driving around with an extra 250lbs in the bed (approx. 6% of 4000lbs) or an extra passenger or two.

I ran 33x12.5's w/ stock gears and a V6 and it wasn't that bad. I didn't think it justified the cost of regearing anyway. With 35x12.5's and stock gears, its another story though (but still perfectly drivable).