No change in tire size.... just looking at towing heavy. I wish I'd have held out for the 4.10s but they are/were hard to find so I just took what I could get. The change to 4.10 gives another 3000# in towing capacity. If swapping to 4.10 is easiest/cheapest I'd likely go that route. I was just thinking as long as I were doing it I might as well see if going up a couple steps made sense. Also, gas is on my company so MPGs really don't matter to me.... within some reason.
Realistically, I'm not looking at towing super heavy and I'll most likely just stick with what I have. I'm somewhat kicking myself for not just getting a diesel but that's just life. I'm not minding having the extra 6K in my pocket now that I would have spent. Overall, I love the Hemi and am pleased with the way it tows. I'm just a weekend RVer and 95% of my miles are spent with no trailer so it's not a huge deal.
If I could jump up to the 4.10s for less than a couple thousand dollars and keep my warranty all intact (so, work done at the dealer I suppose) I'd probably go for it. Otherwise, it's not like I'm in terrible shape with the truck I have.
If you're sticking with stock tires I wouldn't go any lower than 4.10's. That will already be pretty low for those tires. If you ever plan on going to 35's or something then 4.56's may be a good option.
The price to have 4.10's or 4.56's installed will pretty much be the same. The parts will be very similarly priced; it's the labor that's the expensive part. I paid just shy of $3000 for my 4.56's installed including all parts, labor, sythetic oil (which was a lot in my truck with the Mag-Hytec rear diff cover), and tax. I had a few quotes from US shops to do it as well and they were in the $2300 range I believe. So I'd say that's roughly what you're looking at if you have a shop do it. For a dealership to do it I'd imagine you're look at a lot more if they even know how to do it. Honestly I wouldn't ever have a dealership touch a differential on my truck. They're something that needs to be setup right the first time or you will chew up the gears. Having an experienced driveline shop complete the work will be worth it.
You shouldn't have any issues with warranty doing that. For one, the dealership will never even know you changed them. Two, they would have to prove the gears are the cause of the problem if something ever did happen which simply won't be the case. 4.10's will make it easier on your driveline, not harder.
For the record, even if you do change your gears your truck doesn't legally have a higher towing capacity. Any authority will still go off what the door sticker says which is what the truck is rated at with 3.73's. Sure it will tow much better and common sense would tell you that it should be able to legally tow more. But unfortunately insurance companies and a lot of authority lacks common sense. That's only applicable if you ever do get into trouble (accident) or pulled in for an inspection while towing or something.
How quick is that cummins to smoke those 37"s through that 456 gear set?
Ridiculously quick. lol. Sometimes too quick as it breaks loose when I'm not actually wanting it too. I guess 1100 ft-lbs will do that
456"s at a shop is like 1600$ I think..well worth it, u should get better mileage on the why as mds will activate easier.
Very likely that he'll get slightly worse mileage with the lower gears. The higher RPM you end up turning outweighs the other benefits. I lost about 0.5 mpg going from 3.73's to 4.56's. Totally worth it though as the truck is SO much better to drive.