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Axle And Regearing Questions

M

M4Madness

NAXJA Forum User
Location
Springville, Indiana
Over the last day or so, I have been using the search feature exclusively to find the answers I need without having to post the same old "newbie crap". Basically, I want to confirm my findings, and get answers to a couple of questions that I couldn't find answers to.

First, a little background. My XJ specs:

1996 Jeep Cherokee Sport
4.0L H.O. engine
AW4 automatic transmission
AMC (Dana) 30 non-disconnect front differential (3.55:1)
Chrysler 8.25" 27-spline rear differential (3.55:1)
NP231 transfer case
Advanced Adapters Heavy Duty slip yoke eliminator
Tom Wood custom double cardan driveshaft
Rubicon Express 3.5" Super-Flex lift kit (netted 5")
Rubicon Express .75" coil spacers
Rubicon Express Generation 2 disconnects
Old Man Emu nitrogen-charged shocks
Rubicon Express adjustable track bar
Torq Flo 10,000# transmission cooler
31-tooth factory speedometer gear
32X11.50X15 BF Goodrich Radial T/A KO tires
Cragar 15X8 Soft 8 wheels with 4" backspacing
Optima "Red Top" battery
CSF heavy-duty 3-core radiator

I assume that I have 27-spline axles in the 8.25 only because it is pre-'97, although I have read here that some of the later '96 models had 29-spline axles.

I am wanting to regear to 4.56's. It is my understanding that I'll need a new carrier for the D30 but not the 8.25 (if I don't buy selectable lockers). I've found a 29-spline 8.25 at the local auto salvage yard for $250, and am seriously considering purchasing it to get the better axles (I'm under the impression that I cannot upgrade my stock axle to 29 spline.)

On Randy's Ring & Pinion website, I notice that they offer 4.56 gears from two manufacturers -- USA Standard ($155 and supposedly more noise), and Yukon ($295 and supposedly more quiet). My XJ is a daily driver -- will the USA's really be that noisy?

Since this is a daily driver (and driven in ice/snow), I understand that I'd be wise to use a selectable locker in the front (if I go that route), but have read conflicting opinions here on whether I would be better served with a selectable or something like a Detroit locker in the rear. I want the best handling characteristics I can get for when the snow flies. I would want the lockers not so much for "wheeling", but rather for my offroad jaunts when deer hunting when added traction would be appreciated.

Thanks for any and all advice/opinions.
 
You can convert your 27-spline to a 29-spline. You need a 29-spline carrier (acutally just the spider gears from a 29-spline carrier) and 29-spline shafts.

I'd go with the Yukon gears or find another place to buy another brand from. Gear whine gets old quick.

If driven in ice/snow I'd go with a selectable locker in back. That being said, I have a Detroit in the rear and love it.
 
If you want to swap to 29 spline, now would be a good time to put an aussie locker in. It replaces the 27 spline stuff, and you can just slip some 29 spline shafts in. It's a little noisy, but works great in all conditions.

Like the weirdo said, better quality gears are worth it, because you want something quiet, and you don't want to have to do it twice.
 
Will a 29-spline carrier fit in a stock 27-spline housing? One of the reasons I considered buying an entire axle assembly from the local salvage yard for $250 is that most people who set up gears charge at least $100 more to regear if the axle is still under the vehicle. Add in that fee, plus the cost of a 29-spline carrier and axles, I'd have just about as much invested regearing the one currently in my vehicle as I would another one out of the vehicle. Plus by buying one, I could still drive my XJ while I'm waiting on the other one to be done.
 
Yes, the 29-spline shafts will fit, which said changes in above posts. You can always buy the new axle and build it and swap them out. Then you could have a spare.
 
Where are you at in Indiana man? I will probably have a 29 spline here pretty soon that I won't need.
 
Thats not to far from me. I will let you know if I have the axle available.
 
For offroad snow and deeper snow an automatic locker (Detroit, Aussie, etc.) is fine, but if you live where you do and regularly drive on the street on ice and snow you will be happier with the selectable locker.

Some low cost gears can be noisy because they sometimes just don't set up perfectly, and the store doesn't want to warrenty against that possibility. The better gears are worth it.
 
let me throw some personal experiences ive had with my jeep your way. Its setup almost identical to yours except i run a 265/75r16 tire.

First locker i had was a lock-rite in the rear of my jeep. I used to live in missouri and one midwest winter is all that locker got to see. The unpredictable loading/unloading it had on on and off ramps for the clover leaf exits was enough to scare anybody into being spiritual i really felt like i had less control and it was downright scary. I know tons of guys that have never had problems like that, but my experience was such. For the winters you'll encounter id suggest staying away from anything that has the potential to load/unload/slip anything of the sort. Selectable would be best but i think a full detroit would be a better second option than anything else.

Second, i recently changed over to 4.56's in my jeep. I live in a large city and take highways everywhere i go-that being said in my driving conditions for a daily driver the 4.56's would be a tad low. I absolutely love them and wouldnt want 4.10's but dont know if i would want the upper rpm's everyday for a long commute. Normal "around town" driving love it, off-road love it-and theres a chance that driving it around everyday would be fine for me but i do know that everytime i get in my jeep and jump on the highway now the thought is in my head. Just wanted to give you a couple things from someone who has the same setup you have and are thinking about getting.

For a good price on some good gears call eric at national drivetrain-they are a site sponsor and he's taken good care of a lot of guys on here!
 
the_weirdo said:
You can convert your 27-spline to a 29-spline. You need a 29-spline carrier (acutally just the spider gears from a 29-spline carrier) and 29-spline shafts.

I'd go with the Yukon gears or find another place to buy another brand from. Gear whine gets old quick.

If driven in ice/snow I'd go with a selectable locker in back. That being said, I have a Detroit in the rear and love it.
Click to expand...

You need the carrier also,the 29 spline shafts wont fit thru the 27 spline carrier/carrier bearings!
 
Have you considered more of a limited slip for the rear over a full locker? If you aren't doing any heavy wheeling, you won't really need a full locker, and a limited slip type device will be much nicer on the road. Plus, I think they are cheaper.

If you'll be driving on snowy and icy roads a lot, and go on the occasional off-roading trip .... I'd recommend a selectable locker in the front and a something like a Detroit TruTrac in the rear. Heck, even the factory LSDs are pretty good. I know they came in D35s and D44s. I don't know if they came in the 8.25s or not.

When you need some serious off-road traction - lock in the front.

When you just want good traction in the snow, put it in 4x4 but leave the front un-locked.
 
Thanks for all of the replies, guys. I'll address a few:

StylerG said:
I recently changed over to 4.56's in my jeep. I live in a large city and take highways everywhere i go-that being said in my driving conditions for a daily driver the 4.56's would be a tad low. I absolutely love them and wouldnt want 4.10's but dont know if i would want the upper rpm's everyday for a long commute. Normal "around town" driving love it, off-road love it-and theres a chance that driving it around everyday would be fine for me but i do know that everytime i get in my jeep and jump on the highway now the thought is in my head.
Click to expand...

According to the online calculators, 4.10's with 32" tires would put me back to where I was stock with 3.55's and 28" tires (17 RPM's at 60 MPH higher than stock.)

Stock -- 28" tire, 3.55 gears, 1938 RPM's at 60 MPH in overdrive.

Current -- 32" tire, 3.55 gears, 2258 RPM's at 60 MPH in 3rd gear (I don't use OD with this high-geared set-up to get better gas mileage.)

Future -- 32" tire, 4.56 gears, 2175 RPM's at 60 MPH in overdrive.

That's 237 RPM's higher than stock, and 83 RPM's less than what I'm comfortably doing right now with my current set up. I don't even notice the revs right now. I drive 20 miles of highway roundtrip a day to work and back, and never exceed 60 MPH. A 4.0L supposedly gets it's best gas mileage between 2110 and 2640 RPM's. For a long trip on interstates, I could always drive my newer Ford truck.

Also, from the NAXJA Regearing FAQ:

*****"...There is only one tire size that I could see having some confusion. A 32" tire could probably get away with running a 4.10 gear on the highway, and still feel OK offroad. I think you'd be better off with a 4.56 gear, especially if you live in a state with a single hill..."*****

I live in hilly southern Indiana.


billyjp2 said:
some 96 XJs did come with 29 spline 8.25s. check the build date, i believe the ones built in may(?) or later came with the 29 spline
Click to expand...

Mine was built in 3/96. I read somewhere that the 29-splined axles weren't used until 5/96.
 
like i said, i wouldnt want 4.10s in mine personally but dont drive it everyday! The rpm's are a tad high when you exceed 60mph and so i wanted to give you that thought.
 
StylerG said:
like i said, i wouldnt want 4.10s in mine personally but dont drive it everyday! The rpm's are a tad high when you exceed 60mph and so i wanted to give you that thought.
Click to expand...

Yeah, I understand. I was just figuring on the fact that I've been driving it in 3rd gear for 22,000 miles now with the 3.55's, and with 4.56's I can drive in OD at around 100 RPM's LESS than what I am now.

I have a friend with an XJ that he no longer wheels. He's offered to give me a good deal on his D30 and 8.8, but I've passed so far due to the fact that the front has a Tru-Trac, the rear has a Detroit locker, and both have 4.10's. Those would give me fits on a snowy highway.
 
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