I am running 3:55's gears right now and i have 33s but i will be going to 35s and im getting about 20 on highway and 15 in town. Th ejeep also has lots of extra weight from armor does any one know what kinda of milages i would get with 4:88 gears

 

Maybe close to 20 assuming you drive it like a normal person. 65 might be your top speed on the highway. 15/20 on 33s is pretty good.

 

4.88's for a min. would be it, I have 4.56's and run 33's/35's now heavy also wish I had went with at least 4.88's.

 

Out of curiosity, with your 33s and 4.56, what is your top speed?

 

Don't know about top speed but I go 80 at around 2k RPMs with 35s and 4.10s. Before the Stroker, it wouldn't hardly stay in OD though.. always down shifting. I have not ever broken any internals on the D30.. just the housing a couple of times. I have never had a lack of power. Milage with alot of extra metal is right around the 20/15 you are at.

I would run 4.88s but not in a D30. I know people do.. I would brake it. Someday ill throw a 44/60 up front and will gear lower. Not telling you not to do it... 4.88s are the correct ratio for 35s. Just keep in mind they're weaker and if you go with them, adjust your skinny pedal accordingly.

I think ill probably get something like the Behemoth Drivetrain Strongbox before I do the axles again... I'd love to have the extra low ranges for creeping down steep slopes/hills/rocks. Relying on the brakes sucks. Other than that, I like where I am geared with the stroker.

 

I was on 33's with stock gearing, regeared to 4.56 while on 33's and had a huge increase in gas mileage increase & performance. Probably high teens - low 20's. Really noticed it in the distance I could go before filling up. I'm on 35's now and wish I went 4.88's. Do it right the first time, if you'll end up on 35's, go 4.88. I won't regear again, so I'll stick with it. 4.56 is a huge improvement any way you look at it.

 

Really curious on top speed with 4.56 and 33s. If anyone has input on this.

 

150mph at 5250rpm in OD

 

http://jeephorizons.com/tech/rpmchart.html

 

Why do you think you would break it and how are the 488s weaker?

 

Ok great thanks for that info.

 

Thanks to every one els that gave on opinion aswell.

 

http://www.grimmjeeper.com/gears.html

 

Generally speaking, smaller is weaker. By switching to 4.88s, you loose a tooth which decreases the size of the pinion gear. Because of this, the tiny pinion gear will have less contact with the ring gear. So 1st, they are weaker in construction.

Secondly, the Dana 30 is not a strong housing to begin with and most gear failures I have seen/heard usually get blamed on the housing/carrier flexing just enough to cause a misalignment somewhere. Our gears are helical cut which means they try to force themselves away from each other while in motion. I would imagine that the 4.88s would add a bit more leverage to this (longer teeth) making the Dana 30 more likely to flex and cause failure.

All that being said, I think you will be fine running them. I have a heavy foot and need the 30 to last as long as possible for me. Its not like they are glass, you just have to be slightly more careful and with the extra power from the Stroker... thats not something I really want to do haha.

I am not an expert on gears by any means. That is how I understand it and assume why nobody made a 4.88 for the longest time.

 

You are correct. On a regular open differential, when you go too low of a gear, it does have some "deflection" due to the Tq multiplication. That's why a lot of people running lower gears try and put full case lockers or LSD's in instead. Now if you don't plan on driving like Richard Petty or Mario Andreotti, then you will likely be fine with an open style carrier.