Hi guys, new to the forum. I've owned three 2nd gen Cummins as well as a common rail, which I got rid of recently and miss like hell. Anyways, I snagged a great deal on a 01' 5.9l 4x4 Laramie that needs a little bit of love. The truck needs a rear diff and 2 tires, but grabbed it for $1k. It is very clean, especially it being a 1 owner truck. I've got a soft spot for this Gen truck. Anyways, I already ordered a rear 4.10 ring, pinion, diff and the associated install goodies, along with for the front. The truck is a 3.55 truck currently, and has 295/75r16 BFGs. Here's the current dilemma: to stick with the 295s, step down to a 285, or up to a 315. The 295s are very limited in availability, but I like the median size. What is the concensus on tire size for these gears? After a little reading, I'm wanting to kick myself in the *** for not going 4.56s

 

I don't do metric, so you'll need to convert. But my personal rule of thumb is 3.92 or 4.10s up to 33" tire and 4.56 for larger than 33s. But I'm sure you'll get varying opinions on this and this would be for general daily drivers - moderate off road use.

I personally know track guys with 4x2s running 4.88 on stock or even smaller size tires...

 

I've got 265/17R16's on 3.55 axles... I'm happy with the balance between RPM at highway speeds, and acceleration off the mark... anything bigger on 3.55 axles would bog it down too much... so my guess would be 3.92 for 285's and 4.10 for 315's, to keep the driveability balance.

 

I have those exact tires and have done many calculations on which gears to go with, still haven't made any moves, but I'm dying to... anyway 4.10 and 295/75/16 will bring your rpms to exactly 100 RPMs higher than the stock configuration 1991 RPM at 70MPH vs 245/75/16 and 3.55 gears and 1891 RPM at 70MPH which I think is perfect if youre not hauling anything or such. Personally when I do a gear swap I'm going to do 4.56 with my 295/75/16 tires which will bring me to 2214 RPM at 70MPH, puts me in a good powerband for my 5.2.

 

Yeah I know, in hindsight I should have gone 4.56, but it is what it is, and the 4.10s will still serve me well enough. And the only thing I will be hauling Will be a pontoon boat, kayaks, maybe a open car hauler occasionally.