Hello Jeep community!

This is my first time using a forum so be gentle..
I installed 31x10.5 Micky Thompsons on my 96 jeep Cherokee with a straight 4 5 speed manual. Now my 5th gear is basically useless! What my question is, what gear ratio would be best to regain some power without sacrificing much MPG, and is it expensive? Do i need a professional to do install the new gears or is it something I could do with my dad in our garage?

Thanks!

 

Factory you have a 3.07 gear and those tires made it even slower.I'm guessing you need a 4.11 or 4.56 range to get it back to stock feeling.As far as doing it at home it can be but you need a lot of special tools and know what your doing.Most of us have a shop do it for that reason and yes its not cheap at all it takes a while to do it right.And if your going in that far its the best time to add lockers i know its more money but your right there already and do it once vs twice.

 

4.10's its expensive you cant do it yourself, end of story.

 

4.56 to give you some room for later on


Jeep sold the 4 cyl with the AW4 auto & 4.56 gears




.

 

Why can't you do it yourself? All you need is a dial indicator, inch lb, and ft lb torque wrench, digital caliper, gear paint, some basic tools and some knowledge of what you are doing.

 

Shouldnt he already have 4.10s since its a 4 cyl?

 

yes anyone can buy the tools, its the knowledge of what you are doing part. i have a friend who owns a 4wd/ drivetrain shop. the stories he can tell about people ruining r& p sets due to thinking they can do it themselves. only to have to pay him to do it, plus buy 2 new sets of gears. its only been 500 miles , whats that noise i hear coming from the axles ?

 

Yeah if you do one thing wrong you'll end up eating the ring and pinion or worse the diff.

 

With the 4 cyl. you'll probably be best off with 4.56's. No surprise 4th is your new 5th - the 2.5 is stout and can be economical (I've gotten 24 MPG in an '84 XJ with the carbureted 2.5 and A904 automatic) but not powerful in a 3,200+ pound vehicle. There are things that can be done to warm it up, but probably nothing to compensate for the 12% increase in ground speed you made with the 31's short of a turbo or supercharger. Gear setup isn't some proprietary process but does require some expensive tools and great care to get it right, and I suspect you'll look a long time before you find a set of factory 4.56 axles out of an XJ.

 

If overhauling an automatic transmission doesn't scare you, gears are a piece of cake. lol. Really, the advice your being given is worth considerable consideration.

Changing gear sets is not impossible for a savoy experienced mechanic. Look at some videos on YT and make an informed decision. Understand that if you blow it, you just threw about a grand out the window that you could have used for some other cool stuff for your xj.

Google search will get you a gear ratio formula for what gears will get you close to stock performance. Personally, I would go for a little more gear than stock performance if your going to off road the 4 banger very much with taller tires.

My advice is worth exactly what your paying for it....lol

Happy Jeepin'

86 2 door 2.5 liter, 4 speed daily driver
84 2 door 2.8 liter, 5 speed, haven't decided what to do with it.
93 2 door 4.0 liter, auto. complete burn out by PO doing a stereo install, shame, parts

 

I've seen & drove 1....and he just wanted too much money for it for no better condition than it was in at the time.........................

 

I have an 85 with 2.5L and A904(three speed auto no over drive) which has the 3:73 gears. Going up to 235x75R15s(basically 29s) it pulls pretty good. I imagine though with overdrive it would not.

https://www.cherokeeforum.com/f59/ge...e-chart-67989/

This is a good basic chart for seeing how the ratios compare when switching tire sizes. It is calculated using direct gear, not over drive and I think 65mph to calculate the engine rpms.

 

Decent chart. Check out this one though. IMO one of the best out there.

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

Plug in your numbers, sit back, and enjoy the ride...really useful if you want to see different setups and how they will affect your rig

 

Terrible advice. How do you know?

I will say this...BEFORE you regear, make sure you know what tire size you wanna run...you could regear for 33's, change your mind and wanna go to 35's, and you'd have to gear again...also, when you decide what's best for you, decide what ratio works for you and your app, do your lockers/spool/LSD then. Why do it and pay for it twice?

 

You need to hit the road, bro. You have no idea what people are capable of. Some people can't, sure. But those people most likely know who they are and won't try. Some people are unsure of whether they can or can't.... they may or may not succeed. Then there are those that KNOW that they can, just haven't done it yet. There's a difference between cautioning someone to make sure they do AAAALLLLLL their research and know FOR SURE what they're getting into before tackling such a big job, and coming in here like an arrogant know-it-all and telling someone, who they don't even know, they can't do it.

Your attitude is poison... and I'm getting sick of seeing posts of this nature from you. This forum isn't here to tell people they can't do stuff... we're here to help where we can but keep peoples' feet on the ground at the same time. I'll bet YOU would've told me I CAN'T convert my Jeep to 4wd because I wasn't a professional mechanic. Guess what buddy.... 2WD BY THE ****IN' VIN!