Liberty KJ vs XJ 8.25

[TeKdo]

Hey guys, been playing around with some thoughts about an axle swap in my '86 2.5.

 

My '86 feels like it desperately needs a regear after doing my AX15 swap. First gear feels way too tall for the power I make and 5th gear is borderline unusable on the freeway.

 

I thought I would just regear my factory D35 non-c-clip since it has a factory limited slip and I should be able to find some kind of alloy axles to swap into it. Well...turns out alloy axles for the D35 NON-C-CLIP are virtually non-existent anymore in a 27 spline. Definitely don't feel like dropping the cash on a new limited slip 30 spline soooo looking at an axle swap because y'all make me paranoid of having this axle long term.

 

Not concerned with having a locker in the back because just having a limited slip meets my needs more than a locker. Would like to run 4.56s and a current max tire size of 31s.

 

I'm just wondering if anyone has used the Liberty 8.25s instead of the XJ 8.25s. I tha people use Liberty disc brakes to convert the XJs but is there anything else that's different besides that? Mainly because if I have to hack all the suspension mounts to weld on spring perches for spring under axle, why wouldn't I just grab a Liberty one instead of an XJ one?

 

My main concern for the Liberty 8.25 is if it's compatible with the same limited slips that are available for the XJ ones, if the parking brake works good enough to park on hills since my jeep is manual, and if it has 29 spline axle shafts for that said diff compatibility.

 

 

.....also liberty axles are cheaper than XJ axles near me.

 

[watchamakalit]

4.56 will be really deep with 31's. I would suggest no more than 4.11's if you want something highway driveable.   If memory serves 4.10's and 31's are very close to stock final drive ratio.

[Billabob]

If re-welding leaf perches isn't a deterrent, I would highly consider using an 8.8 out of an explorer. 31 spline, disc brakes, and many come with a limited slip.

[ghetdjc320]

KJ 8.25 is about 2.5” wider than the XJ model. Fits the rear of an MJ very well since it is a bit wider at the bed. Lots of brackets to remove but that’s not any real issue. Fairly easy to re-gear since it has side adjusters and a crush sleeve. 
That being said, rock auto has your bolt in d35 1541 axles around $150/ea. Also check with revolution axle and gear. They still had them last I checked. 
I’d stay away from an 8.8 for only 31’s. Too narrow on an MJ and with its large pumpkin, you might as well run 29’s on a d35.  
As for what ratio to run, plug your numbers into grimmjeeper gear calc and see what your rpm’s will be. And measure your actual tire size to use as your number. It’s likely 29”-30” true size

[89 MJ]

4 hours ago, watchamakalit said:

4.56 will be really deep with 31's. I would suggest no more than 4.11's if you want something highway driveable.   If memory serves 4.10's and 31's are very close to stock final drive ratio.

It would make it fairly close to a 4.0 ratio, which probably wouldn’t be much good with the 2.5L. 
 

3 hours ago, Billabob said:

If re-welding leaf perches isn't a deterrent, I would highly consider using an 8.8 out of an explorer. 31 spline, disc brakes, and many come with a limited slip.

In my opinion, there’s a couple of issues with the 8.8. Firstly, they are too narrow for the rear of MJs unless you get one from an Explorer Sport Trac. The other issue is the ground clearance lost. My MJ has an 8.8 and 31s, and I hit the diff when o did some very minor trails. 

[Billabob]

The 8.8 has a 58” WMS to WMS as opposed to the MJ’s 60”. If you plan on beefing it up even more, the semi-float kit puts you right where you need to be. The Liberty 8.25 has a 62” WMS to WMS, which IMO is more problematic. A narrower axle can cause clearance issues, a wider axle will cause handling issues. 
 

This is my first time hearing about pumpkin clearance issues kn the ford axle. How much more does it droop than a D35/8.25?

[Pete M]

a wider rear axe will not cause handling issues.    guys have been adding spacers to the rear axle (without adding them to the front) for years now with no ill effects. 

[Billabob]

I’m sure people have been getting away with it just fine, an inch on each side is hardly cause for concern. However, if the argument here is that the 8.8 is the wrong width then the 8.25 is equally wrong.. and the general rule of thumb is that the front axle should be equal to or wider than the rear. 
 

As for pumpkin clearance, I won’t have time to get my own measurements till next week but I can’t imagine it is significant. If ring gear diameter is any indicator then the 8.8 only sits 1/4” lower than the 8.25. 
 

I’m not sure what OP’s priorities are with this axle swap and they are free to do their own research but the 8.8 should certainly be a contender. 

[schardein]

I agree the rule of thumb is the front track width is usually equal to or wider than the rear.  Use and priorities definitely plays a role:

daily driver- reliability

just want to make it drivable- ease of swap/installation

max effort off road- strength and ground clearance

 

Pumpkin clearance might not be a concern for a daily driver, but 1/4" difference on a off-roader can be the difference between stuck and not stuck.

[Pete M]

being a slightly different track than the front is not the issue here with either axle. 

 

the 8.8 is theoretically wrong because it pulls the tires in towards the bed and can cause rubbing.  plus the bed is already wider than it should be relative to the front and this exacerbates the visual issue.

 

the "same width" is more myth than rule of thumb.   plenty of regular cars/trucks have done it over the years.  like, every dually for example. 

[Ωhm]

Wouldn't rear axle length affect the front tire scuffing, when cornering?

[Pete M]

do dually trucks have an issue with front tire scuffing vs single rear wheel trucks? 

 

 

[Billabob]

Duallys aren’t exactly known for their exceptional handling. An extreme example would be a trike, would you prefer to ride a trike with two front wheels or two back wheels? 
 

Can’t say I’ve ever encountered an Ackermann denier before, lets agree to disagree. 

[Pete M]

we're talking about a whole inch and change difference per side.  taken to extremes (both in large track differences as well as in high speed maneuvering) I'm sure there are things to consider, but I'd wager a large sum that none of us are going to see or feel a change with an inch and a half offset. 

 

I wish Don was around to chip in.   he was one of the first to add spacers to the rear only.