My very first post on the site. Just joined over the weekend. I have a 2004 Ram 1500 with the 4.7. Has 3.55. I've been reading quite a bit last few days. I'm running 285/70/17 mud tires. So basically a 33' tire. The truck is not a daily driver. So gas mileage is not really an issue. I do drive it on the highway and around town. It struggles to maintain speed with either cruise or just driving. Always having to gear down on the slightest incline. I know that 3.55 with those tires is the issue. From what I have read I should go either 4.10 or 4.56. At 70mph I'm turning 1900rpms or so. I do take it to the beach sometimes which is 4 hr trip. Haven't done any towing and will likely not do much. I would like to be able to pull a trailer with my street car on it, which I drag race, if I ever want to go to a track which is far away. Other than that I will not likely tow that often.

Should I go 4.10 or 4.56? I would still like to be able to cruise the interstate when I want. I don't mind losing some mpg on the highway either. So that's not really an issue. If going to 4.56 how much more rpm would I be turning at 70mph from the 1900rpm I turn now with the 3.55? Thanks for any input.

 

If you're going to re-gear better to just go up a whole step. I run 4.56s with my 35's and it's just as peppy as when it had the factory tires and gearing.

 

3.55 gears, 33 inch tires, and 1900 RPM at 70??? That seems a bit high to me, given your combo.

I have 4.56 gears with 33" tires, and its really too much gear for those tires. If you tow at all, on the freeway, you won't like it..... 4.10's are just about perfect for 33's. but, if you want to go to larger tires, go with the 4.56.

 

I can check the tac. Ill just hook up my HP Tuners and open the scanner. See what it reads. But its showing 1900@70mph. The 33's are plenty for me.

 

I just remembered my speedometer is slow by 5mph. So actually at 75mph Im turning 1900 rpm. Thats according to GPS app.

 

That seems reasonable.....

 

I have no intentions of lifting it or going to bigger tires. I climb in and out of a tractor-trailer all day. I dont want climb into my own vehicles. Sounds like 4.10 is probably best for me. And will be a big difference over that 3.55. Which right now is more like a 3.35. Lol

 

I don’t know where you are located, But I just had my gears replaced by EastCoast Gear in Louisburg , NC. They did an awesome. It’s a major business, not a mom and pop, But great service. All bearings and seals. Richmond gears and limited slip unit rebuild.! $1700. One day service.
Note ! They install only Lucas 85-140 Non-Synthetic gear oil. That’s what they warranty. + your OEM limited slip additive .
I’ve owned my 02 since new and it gets 1.5-2 mpg better now 👍👍👍