Replacing Stock '06 Gears With 4.10s?

[Powerslave]

Considering doing this at one point. The jeep would launch better, get better MPG in hill climbs, require slightly less gas pedal pressure. and not rumble at 2k RPMS at 35MPH up a hill... Though I have had this up to 110 already, I don't normally go over 70, so I know that will suffer a little in MPG, but it should even out with the City driving?

What all needs to be changed besides the gears in the DIFFs. Speed-o calibration, other stuff?

AND, what 4.10s will fit?

 

[HoosierJeeper]

With stock size tires, you're better off with your 3.73's....but the 4.10 must come out of a 4 cyl KJ.

 

[KYLiberty]

I ran 4.10's with 29.5" 245/65R17's for a long time. You will get a lot better acceleration and power down low. You will probably get a drop in mpg even in the city because it tends to be difficult to not use extra power. You do not need to recalibrate the speedo for gear changes, just tire sizes. I've got 245/75R16 Silent Armors now. I have Yukon 4.10's for the 8.25 in the rear, and the front diff from a 4 cylinder KJ. There is someone selling 4.10's for the front besides the dealerships now, but I can't remember who it is. I'm sure someone will chime in with their link. Just remember, the 4.10's for a D30 that everyone carries absolutely are the wrong thing. Also, get the rebuild kits, and if you're going to add lockers or lsd's, it would be a good time while the diffs are torn apart. Labor is expensive for diff work.

 

[Powerslave]

Labor is not an issue, that will be free. I do PC work for a few AUTO garages, all I pay for is parts, they install. Nice trade off, keeps me with a healthy vehicle all the time.

SO, I find a KJ with 4-Cly, and yank the front and rear diff/Gears...

 

[HoosierJeeper]

Nice trade off....

Yep....get the gears from a 4 cyl KJ.

 

[tommudd]

Good luck finding a 4 cylinder out there. Not many to be had at all. Just buy the gears and have it done, one member on LOST is selling his front set, rears are super easy to come by. There are a couple fo great threads over on LOST as to where to buy, pricing etc.

Or find some one who is stock piling them and offer them a huge sum of money!

Like this guy

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[HoosierJeeper]

That top one doesn't look to secure on top of the other...

 

[tjkj2002]

If you find a 4 ****** front diff just swap in the whole diff instead of just getting the gears,it will be cheaper and easier then just swapping the gears alone.Labor for free is a good deal since it normally runs about $900-$1000 to swap in 4.10's in a KJ since the front diff needs to completely removed for the gear swap(6 hour job alone).

 

[Powerslave]

Yeah, I was thinking that myself, even with the REAR, just swap the whole rear axle out, rather than pull the DIFF open and swap gears; that is, if it will bolt up the same way. I will keep my eyes open locally for some 4.10s... Just something I was thinking about while bogging up a hill at 35MPH in 3rd/lockup, constantly up and down shifting...

Either way, will be free labor any way they decide to do it.

 

[jsc7002]

Good luck finding a 4 cylinder out there. Not many to be had at all. Just buy the gears and have it done, one member on LOST is selling his front set, rears are super easy to come by. There are a couple fo great threads over on LOST as to where to buy, pricing etc.

Or find some one who is stock piling them and offer them a huge sum of money!

Like this guy

You must be registered for see images attach

hmm it looks like he needs some more CVs, he should buy mine

For the OP if you want to buy just the gears and the rebuild kit TrailQuest has them, I might have a 4.10 ring and pinion set for the D30a in my garage sitting around Id have to check.

 

[tjkj2002]

Yeah, I was thinking that myself, even with the REAR, just swap the whole rear axle out, rather than pull the DIFF open and swap gears; that is, if it will bolt up the same way. I will keep my eyes open locally for some 4.10s... Just something I was thinking about while bogging up a hill at 35MPH in 3rd/lockup, constantly up and down shifting...

Either way, will be free labor any way they decide to do it.

A direct rear swap would not work since you have a '06 with ESP and all that junk and they stopped making the 4 ****** gas KJ's in '05 that did not have your setup.Plus most you will find will be the '02-'03 versions and they mostly had the D35 rear diff which you do not want.A set of 8.25 4.10's and master install kit can be had for about $300,I'd only recommend Yukon,Precision,Richmond,or Motive gears for the 8.25(listed in order of best to worst,do not get the GenuWHINE gears,there called that name for a reason).For the front D30A gears only one company makes them no matter what anybody say's,they all are made by Dana/Spicer but can and will be packaged in another company's box and sold as there product and last I heard Dana/Spicer stopped making them a while back due to the diff is no longer produced or put in a new vehicle as of almost 3 years ago and Dana/Spicer got burned pretty hard by Chrysler when they filed for chapter 11 and Dana/Spicer has it's own problems again.

 

[Powerslave]

Also, sorry, that's 1500RPM up a hill in 3rd gear-lockup, 35MPH... I do want 4.10s, so, will be actively looking in local bone yards...

Also, yep, forgot about the fancy electronics for the rear-axle, so not a simple axle swap for the rear or front....