'88 Mj To '99 Xj Axles Etc...

[shimer]

Hi everybody!

 

So, I have an '88 MJ Shortbed with 4.0L, puegot 5sp., 231 t-case, D35 rear axle, D30 front. I also have my sister's '99 XJ with a smashed up front clip. My brother and I swapped the motor into another XJ that was missing a motor, so I have the rest. Pretty much everything behind the radiator is ok. The '99 has 4.0L, AW4, 231J (I think), 8.25" rear axle, D30 front.

What I want to do is swap the axles, and lift the MJ. Due to the different axle gear ratios, between the 5sp. and auto, and silly vacuum disconnect on my D30, I feel the need to swap both axles and do a rear SOA. My understanding is that, due to differing spline counts, the 231J will NOT mate to my puegot. I don't want to switch to the AW4, so does that leave me looking for an AX/15?

My other quicker option; lift the MJ without the axle swap. Do the SOA with the D35, and swap out the axles later. I don't plan on running more than 33" tires and it is my Daily Driver, so everything has to be done on the weekends ready to drive on Mondays. My immediate goal is to get new tires on it before the snow starts falling up here in the high rockies because the tires are starting to look like drag slicks.

 

Does this make sense to anyone? I'm really just looking for affirmation so I feel like I know what I'm doing before this can-o-worms gets opened up.

Thanks!

Shimer

[Timeless]

Why not put the cherokee axles in and don't worry about the transfer case or transmission. Likely, the cherokee axles will have 3.55:1 ratio gears which might be a little lower than ideal, but it will certainly work.

[Pete M]

the cherokee rear axle will need the perches moved whether you go SOA or SUA. :thumbsup: the XJ perches are further outboard than MJ.

 

I would definitely swap the axles regardless of lift or anything. 3.07 gears suck. :yes:

[Geonovast]

I would swap in the XJ axles (make sure you get a 3.55 speedo gear for your T-case), and call it good. Don't even think about doing an SOA unless you're sinking the money into the front for around a 6 inch lift.

 

Lifting the truck 6-7 inches, you're going to need some big tires on there... and your 3.07 (or even 3.55) is going to not like that very much. I've driven an MJ with a 6.5" lift, 33" tires and 3.07 gears... it was a dog.

 

Putting that 8.25 will require you to have a slightly shorter rear driveshaft without lifting.

[Eagle]

As already asked, why are you considering swapping the transfer case? The ratios are the same, so there is nothing to be gained by doing that. Just swap the axles. If it's the vacuum port on your transfer case you're worried about -- just cap it.

 

Next question: why go SOA? Do you **NEED** 6 or more inches of lift? That's what a SOA is going to give you, as a minimum. To match that in the front, you'll need adjustable control arms (or long arms), an adjustable track bar, extended sway bar links and/or sway bar drop brackets. You'll need much longer flexible brake hoses front and rear.

 

I'll probably catch a lot of flack for saying this, but IMHO running 33" tires on a daily driver is dumb. They are big, heavy, don't wear well, and expensive. Your gas mileage is going to suck, even with the swap to 3.55 gearing. For a daily driver you'd be much better off with about a 2" lift and 31s. Moreover, what size 33s, and on what wheels? Remember, 31x10.50s on factory rims ride VERY close to the springs and the inner fender liners. Mine rubbed any time the rear axle defelcted more on one side than on the other. If your 33s are any wider than 10.5" you'll need either spacers in the rar, or aftermarket rims with less backspacing than the factory rims. And rims with less backspecing then create other issues in the front.

 

Consider ALL the implications of what you're going to do before you start doing.

[shimer]

Ok, that all makes sense. I was under the presumption that the reason for the vacuum front axle disconnect was that the older 231s didn't actually disconnect the front driveshaft, is this not the case?

If doing the SOA really is that big I'll probebly buy some rear springs and keep it SUA. The MJ came on 245/75R16s, off of a Wrangler, and they don't rub too bad as bald as they are. It is a bit of a dog. Maybe I'll just buy the same size tires for now and lift it 3"-4.5". But if I don't have to swap the T-case that makes the axle swap a whole lot easier.

Thanks

[Eagle]

The MJ came on 245/75R16s, off of a Wrangler, and they don't rub too bad as bald as they are.

 

That size is equivalent to a 31x9.50. You don't need any lift to run those tires, so don't lift it unless something changes to create a need.

[Geonovast]

All 231s disconnect the front driveshaft. The CAD in the axle was designed to just cut down on how much was rotating(front driveshaft), in a useless effort to save fuel. It ended up just being a hassle and more stuff to fail, so it was done away with in the early 90s.

[shimer]

Yeah, a friend of mine who has had a few XJs told me the T-case thing. As for the suspension, it sags all the way around. The truck has tow bar mounts, so I have a feeling the suspension saw a lot more use than the rest of the truck. I'm not locked into a particular tire size. We have a few sets of rims laying around, so I can do 15s or 16s. The Wrangler rims look nice, though. I just want to keep the tires skinny so that they will cut down through the snow. I also do a fair bit of wheeling on the weekends, so I do want to get it up a bit.