Gearing question

[chad551]

My ST came with the 4.10 L/S option. I now have my new tires on, which are approx 34". If I re-gear it to 4.56 I know my low end will see an improvement, but what will happen to my highway mileage? Or should I just keep the 4.10's?

And when I offroad will my t-case have enough low-end with 4.10's?

 

[brianjwilson]

I think I calculated this earlier...
http://www.therangerstation.com/tech_library/Gear_Tire_RatioChange.html

A 255/70/16 is 30" tall.
Switching from 30" to a 34" tire with 4.10 gears, makes it feel like 3.62:1 gearing.
To get back to stock you would need 4.65:1, which doesn't exist. So you get 4.56:1 gears and the gearing would still be slightly taller than stock.
I would think it might improve mileage because it won't have to work as hard...?

 

[JohnnyO]

Your highway mileage will likely be slightly worse but that's more an effect of the bigger tires themselves than the gearing. I'm thinking the 4.56's will actually help your mpg over 4.10's with a 34" tire.
I run 32's with 3.73 gears, all off-roading is automatically done in low range. I don't even think about using hi range. Generally I use low range with the gear selector in 2, and dowshift to 1 manually if I need. It is very hilly here with some deep mud but I've never had a problem. .02.

 

[N2FORD]

I think some of the guys have been running 4.88's with 35's. 4.88's will help that bottem end and not hurt to bad on the highway. I don't know the availabilty of 4.88's for the ST though.

 

[brianjwilson]

Yep, I'd go with 4.10's up to 32's, 4.56's up to 34's, and 4.88 above that, depending on driving.
It seems like I remember there being an issue with 4.88's in the front diff but I don't remember for sure.
I REALLY want to re-gear to 4.56 gears but the lowest cost I can find is about $1300 total, so it's not happening any time soon.

 

[JohnnyO]

I was told that 4.88's for the front recently became available.