I was just wondering what kind of gas mileage loss I would expect from going from 3:55 to 4:10?
I am running 245/75/16 tires and have a 5.2

 

with the 5.2 and a heavy truck you can exspect better milage if you keep your foot out of it

 

Thanks for the input....may go 4:56's, I was kinda thinking it may be too much when I tought MPG would go down.
A question for the mechanics......
I was planning on going to the junk yard to look for one and the diff will be drained of fluid. How long would it be before the gears start to rust if at all from no fluid?
Also what is a good way of checking everything out while it is still in the rear end?(planning on just pulling the whole thing out over tearing down both.)

 

They shouldn't rust unless they were in a flood or something. A 4.56 with that tire will be way to much gear.

 

Stock tire size stock gears, MAYBE go 3.92. Bigger tires than stock then bigger gears will make good.

 

+1. You'll spin tires at every stop light if you gear that low with your current tire size

 

Thanks for the input guys.
I am thinking I will more than likely run into 4:10 or even 3:92.(4:56 at a JY seems like a long shot)
The reason I am thinking of stepping up gears is from what I read the 3:55's blow for towing and I plan on towing a Travel trailer this summer and will be towing it a pretty good distance.

I have read that the 3:92's aren't really that much better than the stockers, anyone have any input on this?

Also, what tire size would be recommended for 3:92's or 4:10's?

 

https://dodgeforum.com/forum/2138088-post10.html
In this post it says that if I had 3:92 and go from 245/70r17 to 35x12.5x17
My ratio would be less than stock, so how would having bigger tires help?

 

Larger tires effectively give you a lower (numerically) gear. What you need to do is, decide what tire size you want to end up with, and gear your truck accordingly. If you eventually want to end up with 35's, (which will also require about five inches of lift, to prevent scrubbing the tires against various body parts...) 4.56 gears will keep you close to your current "stock" rpm, for any given speed. Since you say you want to tow regularly with your truck, 4.88's will give you a nice boost with the 35's, and will only effectively raise your rpms 200-300 from stock, for any given speed. That will put the engine further into the power band, so, it won't be working quite so hard to turn those monster meats. Your transmission will thank you.

 

I am sorry I didn't specify earlier. I wont be putting 35's on but may go 265/75's to go with a 3 inch lift in the future. It depends on how empty the wheel wells look and when I have the extra $.
What I am really wanting to do is pull a Travel Trailer without putting a lot of strain on the trans and I hear the 3:55's aren't worth a crap for towing, can anyone shed some light on the truth to this?
Also if I do end up buying the bigger tires after the lift it will lower my ratio more. I know I could get the parts cheap if I can find them so it seems like a worth while investment if its actually going to benefit my situation.