Gearing for 31" tires that won't blow the mileage

Re: Gearing for 31\" tires that won\'t blow the mileage

You might consider the 4.1 as "power" gearing and the 3.73 as the "economy" gearing (better gas mileage and less power), but if you intend to go to 33s, by all means go with 4.10. There is something else more important you need to consider, however.
The Dana 35 will be a reliable axle UNTIL you put a locker in it. Don't misunderstand. If you lock a D35, it will not fall out of the Jeep when you back out of the drive way. It will work, but it can also get broken very easily. If you intend any time in the future to do any kind of off roading that will require a locker, you might consider installing a D44 now instead of investing money in the D35. Locker and gears for the D35 are basically the same price as those for a D44. One serious breakage of the 35 that takes out an axle AND the ring and pinion (r & p are less likely to be damaged, but could be) will just about make the difference of putting a D44 in now, and depending on the deal you can find on a D44 housing, could be even cheaper than repairing the first D35 breakage.
I have seen more than one D35 break on the very first off roading event, but in all fairness have to say that I have seen them last for a long time too. Depends about 90 per cent on driving style and 10 per cent on luck, but just a few too many rpms, a little wet spot on a hill and then hitting a dry spot is all it takes. Not talking 3,000 rpms either. 1,500 or less will do it.

Doug '97 TJ
Creator of the CBrack
My Web Site

Re: Gearing for 31\" tires that won\'t blow the mileage

Well, I just got brand-new 31" tires and will be gathering up parts for a serious build-up for the next couple years that I plan to install all at once, so as not to have a weak link. I can pick up a set of Wagoneer axles for $300 with a factory posi-lock in the rear, but will have to weld new perches, run brake lines, and re-gear them as they are most likely 2.73 or 3.03. Are you sure that 31" tires can break a Dana 35C with a stock drivetrain (ok, *slightly* more power than stock?) I play in the mud an regularly see "high" rmps while in low range- say up to 3000-3500 rpms. I also try to find some good hills to climb but I do lve in Florida and there isn't much to be said for "hills" here. Ocala National Forest has everything that I would expect to see. I have seen quite a few Jeeps around here running 33" tires on stock axles- but without a locker. Does anyone make a 4.00:1 R&P? This would seem like a happy compromise. How much higher would it raise my RPMs to use a 4.10 ratio, seems to me like I would just get more use out of my 5th gear overdrive. Does anyone have stock 4.10 gearing in good condition that they would like to sell me? All the 4-banger YJs came with 4.10 gears.