Need Help with Diffs! - Re-gearing, Ratios & Lockers

Hey guys. I'm thinking of up-sizing my tires to 33" mud terrains for some extra traction. I'm not a hardcore wheeler, but I do like to have some fun in the mud sometimes. My Cherokee is a semi-daily driver, and I use them on all camping trips on asphalt, dirt roads and off-road trails.

I have a 1999 Cherokee, automatic, 4.0, 4wd. The build sheet specifies that it originally came with 8.25 Chrysler with 3.55 Rear Axle Ratio, with 28.3" wheels. No word on the front axle, but I'm assuming its the same (please correct me if I'm wrong). I currently have the above mentioned gear ratio, and have 31" tires.

I understand that going up to 33" may require some re-gearing. I would like a nice balance between highway driving and some light wheeling. I found some re-gearing calculator which estimated that somewhere around 4.14 ratio would be ideal to match original design intent for my Cherokee. I don't know if this is true.

I would like to put LSD in the rear and air/E lockers in the front. What do I need to know in order to make all this happen? Do I need to re-gear and then install the LSD/Lockers? Are the front and the back the same? Am I able to do this myself? Am I in over my head?

With your guys' help, I believe I can do anything.

Thanks!

Dana 30HP up front but same ratio.

Go 4.56. 4.10s work but with 33's 4.56 is a solid ratio with a AW4 and if you're regearing do it once and be done. I ran 4.10s on 33's and it was ok, was my daily and around town was fine but whenever we went to the hills I always wished I had deeper gears.

Use this calculator for any gearing. The generic one with colors is garbage.
www.grimmjeeper.com

8.25 are very limited for aftermarket traction support. Great axle but sucks for traction options. Ford 8.8 is a good cheap swap and you'll gain 31 spline shafts, disc brakes and a factory LSD. Factory LSD isn't the greatest but more options for aftermarket support.

Trutrac rear and ziplocker upfront is a nice combo. With both of those they are also your "carrier" so you would install the gear along with those. If you go lunchbox route you'll need to upgrade your carrier.

I'd have someone install your gears. You can DIY but if you f it up plan on buying all new stuff. A lot of time members in your local chapter can hook you up cheaper than a shop.

I don't think there's a need to swap to an 8.8 just because traction devices are limited......that's crazy and part of the cookie cutter offroad forum idea. Go to pirate and everyone needs triangulated 4 links and 1 tons. An axle swap is clearly not something this guy needs. There are enough options for both axles.

I always recommend to run more gear than what a calculator says gets you back to stock RPM. I'm actually running 33's and 5.13's with an AW4 and totally love it. Not a DD but cruises fine at 60. I don't recommend this for you, just saying more gear makes it a more pleasant driving experience.

With 4.56 gears and the AW4 auto (0.75 4th gear) and 33's (33's will measure out to 32" at most installed on the vehicle) you will be at 2500 RPM at 70 MPH. About 2150 RPM @ 60 mph. I think that will work pretty well.

The_Punisher said:

I don't think there's a need to swap to an 8.8 just because traction devices are limited......that's crazy and part of the cookie cutter offroad forum idea. Go to pirate and everyone needs triangulated 4 links and 1 tons. An axle swap is clearly not something this guy needs. There are enough options for both axles.

Click to expand...

8.8 was just tossed out as an idea

As said 8.25 is a great axle and will suffice for what he needs but traction support sucks.

smokeyyank said:

8.8 was just tossed out as an idea

As said 8.25 is a great axle and will suffice for what he needs but traction support sucks.

Click to expand...

What parts are limited in availability for the 8.25" ???

They make plenty of lockers for the 8.25”. Like i can’t think of a type of traction device you can’t get for one.

Spool. I’ve never seen a spool for a 8.25

Wow, thanks for the info. Everyone here never disappoints. Before I started modifying my Cherokee, I didn't even know how to change oil. I always refer to this site, and Bleepin' Jeep, hahah!

I'm almost 100% convinced that the 4.56 ratio is the one for me. My only concern is that I do a lot of highway driving, averaging 70-75 mph. The Grimjeeper calculator show that the 4.56 setup will make my engine run around 2750 rpm at that speed. That seems a little high, but that just means a little less fuel economy and pushing the engine a little harder for but long periods of time. That's not too bad right?

Seeing how expensive the LSDs are, I've decided to ARB everything. Might as well since I mostly drive on asphalt.

Good call on the re-gearing. I was a little worried that you guy's would've said to do it myself. I would have just torn the thing apart! I'm thinking selling my Kia to get a whole bunch of these upgrades along with some stashing some away. I better start buying parts before I change my mind.

Just for shits and giggles. I'd appreciate it if you take a look at my build plan. I'm upgrading from 31" to 33" tires (same wheels)and adding a spare.
I'm also raising my 3" lift a little higher with leveling kits to accommodate for the larger wheels and the weight from my camping gear and armor. I've already cut the fenders off.

This is a first pass at searching for the right parts at the right cost. I wouldn't take this too seriously, but your opinion on whether or not I'm headed in the right direction would be gold.

Try this link if that other one didn't work....

https://image.ibb.co/j4dYaT/Capture.png

I stand corrected. I thought selectables weren't an option for the 8.25 beaides an ox but its zip locker you can't get for it but yes arb is an option. Soooo my bad.

Go with a full SYE vs the hack n tap.

http://www.advanceadapters.com/products/np231-sye--new-process-231j-fixed-yoke-kit-50-7906--50-7907/

Gears go through a vendor
www.RWKHausSupply.com
or
https://www.justdifferentials.com/

Also will need a (master) install kit with both front and rear.

Also for you'r ARB's you'll need the compressor.

I'd personally go with ACOS vs a spacer. Allows you to fine tune the front. As for the rear go with shackle relocation.
https://www.ironman4x4fab.com/product-page/xj-shackle-relocation-brackets-bare-steel

Just did the ARB 4.56 d30 8.25 and added a disk brake setup with JK 32" take-offs (at true 32" OD tire) on my '01 w/auto. 2750 at 70/72 is the rpm I see. The 4.0 will run all day with this. MPG before was 16 now 15.5 - IMO it's the perfect setup for me. Yes get the SYE. I got mine from Tom Woods and used a 6* shim on a 3.5/4" lift. Vibes? yeah, a touch at 70+. Oh, and I used JKS adj. control arms to dial out the death wobble.

smokeyyank said:

Go with a full SYE vs the hack n tap.

http://www.advanceadapters.com/products/np231-sye--new-process-231j-fixed-yoke-kit-50-7906--50-7907/

Gears go through a vendor
www.RWKHausSupply.com
or
https://www.justdifferentials.com/

Also will need a (master) install kit with both front and rear.

Also for you'r ARB's you'll need the compressor.

I'd personally go with ACOS vs a spacer. Allows you to fine tune the front. As for the rear go with shackle relocation.
https://www.ironman4x4fab.com/product-page/xj-shackle-relocation-brackets-bare-steel

Click to expand...

I'm not just trying to argue with everything you post, BUT......

What's wrong with a hack n tap? How many do you know for sure have failed and failed or were less than ideal specifically based on the fact that it was a hack n tap and not some other variable?

My jeep has a hack n tap and over 350 hp and 350 lb ft and the throttle blade is only ever open all the way or closed.

POLAR_JEEP_04 said:

They make plenty of lockers for the 8.25”. Like i can’t think of a type of traction device you can’t get for one.

Click to expand...

No E-Locker available.

The_Punisher said:

I'm not just trying to argue with everything you post, BUT......

What's wrong with a hack n tap? How many do you know for sure have failed and failed or were less than ideal specifically based on the fact that it was a hack n tap and not some other variable?

My jeep has a hack n tap and over 350 hp and 350 lb ft and the throttle blade is only ever open all the way or closed.

Click to expand...

Meh, its the interwebs. For the cost difference might as well just do a sye. Really what's the advantage you gain saving maybe $150 tops? HnT isn't terrible but its not really a negligible cost difference vs doing a new SYE.

smokeyyank said:

Go with a full SYE vs the hack n tap.

http://www.advanceadapters.com/products/np231-sye--new-process-231j-fixed-yoke-kit-50-7906--50-7907/

Gears go through a vendor
www.RWKHausSupply.com
or
https://www.justdifferentials.com/

Also will need a (master) install kit with both front and rear.

Also for you'r ARB's you'll need the compressor.

I'd personally go with ACOS vs a spacer. Allows you to fine tune the front. As for the rear go with shackle relocation.
https://www.ironman4x4fab.com/product-page/xj-shackle-relocation-brackets-bare-steel

Click to expand...

Thanks for the suggestions! They are all welcome. I have a few questions and responses....

1. SYE kit- Your suggestion is for 231, I have a 242. I think I've found a few that have the full SYE for the 242, but they are very pricey.

2. Gears - I'm definitely going to purchase one from a vendor. But curious. What is the advantage of buying from a vendor other than good relationships?

3. The ACOS is out of my price range, especially when I see the plastic or aluminum ones for about $30-$50.

4. What are the benefits of a relocation bracket vs. a shackle extension? The relocation bracket looks very heavy duty, and also expensive.

atriot:

The assumption is if you can afford ARB's then cost isn't the issue.

the hack & tap w/ a new custom built cv driveshaft behind my 242 has worked great for 4 yrs , w/ lots of hard wheeling on it too. the sye kit for a 242 is way too much money. imo.