I’ve searched and read a number of threads here regarding gear ratios, but I am still feeling a bit unsure.

I have a 03 V10 Ex 4x4. Gears are stock 4.30 (C3 axle code). I run 285/65/16s, may run 295/75/16 in the future. I’ve been considering re-gearing for a while because I tow and feel like the transmission won’t sit still when I climb. My rear diff bearings are in need of replacement so I’m planning to change gears at the same time for front and rear.

There’s a bunch of opinions, but I’m looking at going with 4.56 gears. Any thoughts, advice? Thanks!

 

My thoughts and opinions……….
Don't fear the gear! My EX came with the more common 3.73 gears and swapping up to deeper gears was the single best mod I have made to my tow rig EX, period!
I started off towing a 9,500lb TH and it was a dog, it would get us to our destinations but only after a lot of downshifting, higher revs and frequent gas stops. In stock trim I was getting 6 to 7 MPG while towing on mostly highway trips. I swapped in 4.88 gears and on the next trip to the same general destination at the same speed over the same route pulling the same TH at the same weight I got 9 MPG. And it didn’t downshift a single time on the highway between Philly and SC, and it pulled like a locomotive and was a hot rod around town unloaded. I went with the 4.88s because I had new 35” s in mind and wanted to get to an effective 4.30-ish gear ratio, once the new tires were on and the math was done it’s at an effective 4.39 ratio. After the gear swap I also installed a set of Banks long tube headers and custom tunes from 5Star then we upgraded to a new 41’ (hitch to bumper) 3 slide TT that scaled at about 11,500lbs. With all of the mods and the new big TT I now see between 8 and 9 MPG on our mostly highway trips with a few trips over 450 miles that hand calculated to 9.5 MPG. Over the 11.5 years that we have had the EX we have logged almost 80K heavy towing miles with about 13K of those miles last year with the TT porked up to almost 13K lbs with a few new mods, toys and for many of the miles a full fresh water tank. Even at the extra heavy weight for our long trips last year (PA to WY in the Summer and PA to West TX in the Autumn) we still managed to average almost exactly 8 MPG.

What do you currently tow?

 

10k TT, 33’

 

Yep, go with the deeper gears to offset the taller tires and keep your effective 4.30-ish ratio, or go a little deeper!

 

What would be the benefits/drawbacks of 4.88 over 4.56?

 

For the V10 4.88 for 35" tires and 5.13 for 37" tires

Calculator here if you wanna play with the ratios and tire sizes
https://purperformance.com/p-29669-rpm-calculator.html

 

With your 33”-34” tires the 4.56 gears will get you back to the 4.30-ish effective ratio, the deeper 4.88s will net a deeper effective ratio. The deeper gears will tow better but can knock your unloaded MPGs down a little. When I had 32” tires and the 4.88s it pulled awesome but the unloaded mileage dropped from 14-ish to 12 on the highway unloaded. With my current setup of 4.88s and 35”s it still pulls very well and can get 14.5 MPG unloaded at 65 MPH. My rig is a dedicated tow rig and only sees unloaded driving at our travel destinations, no daily driving.