95black

Rest things first: I've searched hours trying to find an answer and haven't gotten a straight one so I'm hopping you guys can help me out..

A little about my jeep: 95 xj 4.5 inch lift
Brand new 31x10.50R15 on M/T aluminum wheels
Dana HP 30 up front Chrysler 27 spline 8.25 in the rear stock 3.55 gears no lockers
NP231 case and AW4 auto tranny. She's got 235xxx on the odometer and still kickin
It's my DD and she sees a lot of highway, city and mud
No crazy rock crawling on hard wheeling

Situation: I'm stationed in Germany and am having a shop do the work for me unfortunately.
I just need some help from PERSONAL experiance, I've looked at too many calculators and other sites to answer my questions so hopping y'all would have some valuble info for me!

Poblem: I've detonated my rear end, suspected to believe the spider gears have gone by by. My xj will not move in any gears and in 4wd, it will however spin the passenger side tire when given throttle. (yes the shop will determine the complete problem but this is my assumption.

Plan of action: Since IF it is the spider gears that have given out and the fact I'll be replacing hem why not upgrade?
I was going to do a lunch box locker in the 8.25 27spline. This way I can replace the spider gears and not worry ever again!

Question: okay down to brass tax, my questions are
I'm going to regear the jeep I've found a kit for front and rear 4.10s and 4.56 for the same price
My question is what should I choose? I love possibly having more power, I like fuel economy but who doesn't?
I'm stuck between the two.
I have brand spanking new 31s. I know his question is asked countless times but it never really gets answered.
I'm just looking for y'all's personal experiences to see what Mrs Khaki (Mrs. K for short) will like best gettin her booty down the road.
There's a high probablilty once these tire wear out I'll be switching to 33s..

My next question, people say ditch the 27 spline and get a 29. In my current situation that is not an option.
But I may be doing a couple burnouts on the street... You know to umm blow the cob webs and carbon out the motor haha,
But anyways am I going to need stronger axles to support the locker and gears in my rear end?

Thank you for the help and hope to hear some replys!

Fred/N0AZZ

First off I would scrap the 8.25 27 spline and pick up a complete 29 spline from a JY they are cheap and a HD axle to boot direct swap no repairs.

Are the Lunch Box lockers available for the 8.25 even? I upgraded mine not long ago gears and lockers, I used Detroit Lockers on mine front and rear. The gear package I bought from Rustys Off Road both gear sets and master install kits included with them $455 complete for my 4.56's.

You are aware that going from a 3.55 gear to a 4.10/4.56 that your D30 will require a new carrier for the lower gears unless you go with a locker up front also. I am running the 4.56 gears with my 33's and wish I had gotten the 4.88 instead in case I decide to upgrade tires. I notice you have a 4 1/2" lift as I do and at some time you may decide to go up also then a 4.10 would not be as good a choice. Now with a 31" tire 4.10 gears will bring your XJ back to what stock gearing was from the factory on stock tires.

95black

Thanks,
I know I should scrap it but I'm stationed in another country and the jeeps back home, so I won't be scraping the 8.25 and they do make lunch box lockers Spartan, lock right and the powertrax no slip they're harder to find but they are out there.

The rustys gear kit is what I was looking at can't beat the price compared to buying everything separate. And yes I know I need to pick up a new dana 30 carrier rustys has one for like 80 bucks I think.

I do plan on going with a higher lift in the future but I won't be going bigger than 33s

SeriousOffroad

I'd recommend upgrading to 29 spline shafts.

You can keep your existing housing but you'll need a new carrier, so a full-case locker would be a wise choice. ARB or Detroit are available to accept 29 spline shafts.

Low-buck gears may seem appealing but “The bitterness of poor quality remains long after the sweetness of low price is forgotten”.

JD Cravin

If your spider gears are gone, you might as well upgrade to the 29 spline as all you need are the new internals (and shafts)....which you need anyway.
Since you are planning on 33's...and a locker, the 29 splines are the way to go.
I have 33's and 4.56 gears and love it. The engine it's back in the factory power band and feels great....drives great.

cleenrob

well from personal experiance i have 4.10s and 33s and its not terrible. but id rather have 4.56s. if you know your gonna go 33s go 4.56, and deal with high rpms till you get your 33s

as far as a locker check out Lokka lockers super cheep and awesome

95black

Thanks for the responses guys I feel stupid I didn't think about just throwing 29 spline axles in it.. And I'm hopefully getting leave soon and if it gets approved I plan on doing a trip to the beach bout 300 miles round trip.
With 4.56s and 31s is it going to be a mistake?
I hear people talk about 2500rpm being the motors golden number to perform at. But at the same time I'd like to be able to listen to music rather than hear my motor singing Jesus take the wheel...

cleenrob

4.10s and 31s will put you at right about stock rooms

4.56 and 31s will put you 2-300 rpms higher than 4.10s will. (This will be super tourquey)

if your planing on 33s in the near future, jump straight to 4.56. 4.10s and 33s aren't terrible tho

muffinman

FALSE!! 29 spline shafts will NOT fit in a 27 spline carrier regardless of what spline spiders you use. They are a larger in diameter than the 27 spline carrier.

95black

I know I may end up getting a new carrier or going with a full size locker
I'm just trying to keep this under $2000 but thank you for the heads up

Outlaw Star

^you beat me to it.^ This is the basics of what you need gear wise.

95black

Thanks for the help guys!

95black

Actually one more question.. Instead of spending the money on a new carrier and axles
Are the alloy USA 27 spline axles strong enough to use and occasionally abuse along with the lunchbox locker,
4.56s and the 31s ?

SeriousOffroad

Oh yes.

Fred/N0AZZ

Rustys sells Motive gears in their packages at least that is what I received. As for poor quality I question that I have ran Ford 9"'s in most all of my door cars and street/strip cars. I had 2 sets of the Motives for my last setup a SBC 427 ci. on the bottle 950 HP one set of 4.10's for 1/4 mi and 4.88 1/8th. All transbrake launches on them god only knows how many never a failure, did destroy a few driveshaft's and axles along way though. The only reason I had the Motive gears was another racer gave them to me for a set of my used slicks, I had no idea if they even had a single pass in them.

Surprising what you find out sometimes by accident cheap yes quality well I bought this set for the XJ from what I learned on my race car. They will never see the HP or Tq. in this application to what they held up to before, who knows they might throw craps tomorrow if they do I will tell everyone I owe no one nothing good or bad.