I have 4.56 gears and spin 38x15.50's. The gearset in mine is Yukon, and they make absolutely NO noise whatsoever. I love them for the reduced load on the trans and return to the correct power band for the engine, but could have gotten away with 4.30's. As for the pinion being smaller... in my opinion, while true to some extent, that's splitting hairs a little. I doubt the minimal difference in a real world size comparison between the two would be enough to cause a failure, but again, thats just my opinion.

Also... the gear set does not affect speedometer readings. My speedometer went down 10% from stock with the tires. When the gears were changed, it stayed 10% off. Only a tuner reset it for the tires. The speedometer reads off of 3 sensors on our trucks. Each front wheel has a tone ring, and the rear differential carrier has a tone ring mounted with the ring gear. Because the front axle tone rings at the hub, and the ring gear mounted tone ring all move directly in relation to the wheel, speed is measured as the *actual* wheel speed, and not a factor of gear ratio (as read on most Jeeps in the transfercase).

 

I get about the same, but I run 33's & use the spartan 210. Pulls like a beast once you get rolling.

 

Only a tuner reset it for the tires. The speedometer reads off of 3 sensors on our trucks. Each front wheel has a tone ring, and the rear differential carrier has a tone ring mounted with the ring gear.

I believe the front hub tone rings are for the ABS.

 

nice truck by the way...

MY truck....when I first put the gears in I was running the Toyo AT and there a very quiet tire. I'm now running the toyo MT and I they are quiet for a MT but still hum a little. I doubt I could hear the gearset over the tires at speed with the MT.

I also agree that you need 4.56.....you need to overcome the wind Resistance (anything over 45mph) and a 38"tall x 15" wide tire so to be close to stock you would need to over gear it a bit...

did you have the 3.55 or the 3.73 gears in your truck?

did you look at the gear set side by side? you'd be surprised at the difference in pinon sizes.

thats why I would stay with the 4.10 or 4.30 if the OP is going to tow heavy..theres a reason why you can't get a real low gear set with the sterling 10.5 from the factory. plus it would scream on the highway

I'm in the rock crawling thing and we grenade ring and pinons alot..also there a certain cut off for most axles (IE Dana 60 and 5.13 or 5.38gears)that the pinon and gear mesh is too small and will strip the teeth off the pinon from the torque when climbing.

 

Thanks for the compliment on the truck.

You are correct about the ABS on the front tone rings. I thought I had read somewhere that the computer had tracked all 3 sensors for speed, so the front tone rings served a dual purpose. This was one of the limiting factors that the dealers could not adjust for over 35" tires. Something about how the computer could but the ABS module couldnt, so there would be a discrepancy, causing the ABS light to come on. Could be wrong though. Read that a long time ago.

Stock, my truck had 3.73 gears. I held each pinion, but did not compare them side by side. Definitely not disagreeing with you on the fact that the smaller pinions will be weaker. Sounds like you have the first hand experience to back it up as well.

I should have been more specific, but with the original poster asking about the difference between the 4.30 and 4.56, my opinion was THAT particular situation was splitting hairs as far as pinion strength, considering the 10.5/10.25 rear axle can go as deep as a 5.38 ratio.

 

Id like to go 6" and 37"

but I gotta keep this one a tow truck.....