JeepcoMJ

Bottom line. Anyone looking at dropping the MPFI from their 87+ 4.0 for a gain of 30hp has no idea what they are doing, or is one stubborn old s.o.b. That this topic is even being entertained is abhorrent, and an affront to any current age mechanic.

You can use your motor, but need the head off the cherokee to do it right. The ports on the heads don't match up Basically you can use your short block but will also need the timing cover off th cherokee.

Pfft. -17 straight temp here, in WI, -41 windchill. I'm nice and toasty in the shop. How bout that jet stream shift causing a cooling cycle, negating any chance of global warming existing. Eh? Eh!?

That is the factory chip guard tape over the edge of the door frame. You should seal up that gap where the seam sealer has allen out, though

There is a difference in height

The mopar per led units are bleedable via an Allen head screw on the slave. The slave is plastic. They do not hold up well. Aftermarket slaves are available in steel for around $80 through advance auto.

He. already did that

I have seen sometimes that shift towers are also different between the two. If you have a YJ shifter crammed in an xj tower, it would be pretty tight.

I was thinking that, but couldn't remember. Been awhile since I have had a 231 apart

Am I the only one bothered by this statement? The 86-90 4 cylinders have NOTHING in common with the 4.0. You cannot swap the throttle bodies or any parts in between for the one pure and simple fact that the 86-90 4 cylinder is throttle body fuel injection. The statement of popping a 4.0 throttle body only applies with like-year 4 cylinders and 4.0's from 91 and up, because they are both multi port fuel injection.

True. The 242 doesn't really need them, though, as the differential can and will take up the difference in slack to allow for shifting. Either way, shift on the fly is still low speed with a tcase.

Hesco tstats. the 2.5 is the same mounting as the 4.0, and are compatible, if I remember right.

The best case you could possibly get is a 96+ from any xj or zj. It has sealed output, making it possible to drive home if you lose a rear ujoint in part time 4x4. Now, the input IS a medium input. But. The Ax15 has a very long tailshaft in comparison to some, and the medium input will work perfectly fine on an Ax15. The spline goes easily another 2" inside the output housing, and there is absolutely nothing in the way that would cause an issue with installing that transfercase on an Ax15. My 99 XJ was 4.0/ax15 with a 242 from a 96 XJ with AW4. Medium length input. Zero issues with fitment. Does the Ax15 *need* a medium input? No. But it really is a moot point as there is more than enough room to use one. I'd also suggest this point: Benefit of 242 over 249 and 231 242: 2x4: Summer fuel mileage and fair weather. Wonderful to have as an option. 4x4 Part Time: full lock front to rear (slip determined by axles only, i.e. a locker or trac-lock will limit slip and give you more control vs. a 249) 4x4 Full Time: Same function and feature as a 249, without the potential failures of a hydraulically controlled slip. User friendly, performance similar to a 249 Neutral (as all have) 4x4 Low Range: Unlike the 249, this 4x4 low range is a full lock with zero slip potential in the tcase. It gives you the stability and control that you want, in the instance that you need low range. I left my xj in full time pretty much all the time. It was fun. Some nay-sayers will tell you that a full time tcase cannot work behind a manual transmission. They are incorrect in that. The negatives of a manual with full time are that, if you coast in neutral, the tcase will function as though there is a slip and act accordingly. Fortunately, this is just a result in the planetary assembly taking up the slack and rotating until it "binds" between front and rear axles, and I will coast as well. This cannot damage the case in any immediate way (it will necessitate more frequent fluid changes to inspect for wear, but not hinder performance so long as maintained). The reality is that most people don't coast in neutral. It doesn't take but a split second to shift, so the potential backfeed to damage synchros is minimal at best.

In no way am I being mean. I am stating the relevant information regarding they swap and that there are good choices and bad. The 249 is up to you. The zj axles have zero benefit.

The axles have nothing to do with. It. Both axles are junk from zj, and no factory jeep Dana 30 has limited slip. The rear diff can be had in d44 or c8.25 with trac lock and function identically. Not a problem. Axles shouldn't have anything to do with your choice in transfercase.

Grand axles are junk no matter what you do, and the viscous coupler is not limited slip. It is a viscous coupler. Entirely different things, similar principles, but as stated wear excessively. They would not hold up for what you need, either. And all grand axles are low pinion, front and rear.

Above and beyond that, the 242 functions literally the same with a more reliable system than a 249. If you are so worried about the hassle of shifting, you can literally leave it in full time all winter with the same result and better reliability.

First, the 249 does NOT have limited slip in the case. They have friction pads or discs that hydraulically lock and unlock, but they are the weak point That is in the rear axle and is an option, not a guarantee. The rear axle from a grand cherokee, no matter which, is junk. They never came with a good axle. They have the d44a which is aluminum diff and get replaced more often than not, they've a tendency to spin carrier bearings. They are also coil sprung and the mounts are completely different. The cherokee or comanche Dana 44 are the only good choices for factory Dana 44, and the xj one needs perches welded on. MJ ones are getting hard to find. Driveshaft lengths vary by transmission and rear axle option, not transfercase, but obviously require that the yokes on the transmission match the shafts

Actually, there is equal power from front to rear with both cases, and it is evenly displaced except when a wheel slips. A 242 basically has a differential with planetary assembly inside. It is stronger, more reliable, less prone to failure.

Same shafts if the yokes are the same. And you mean Dana 44, not Dana 45. And out of an xj or MJ at that so it is the correct lug pattern and not a p.o.s. Like the aluminum housing d44a from the zj or WJ. Those always spin bearings. You are possibly the first person I have ever heard say anything good about the 249. The 242 is best of both worlds, chain driven with a planetary assembly instead of viscous coupler. Trans mount, you can do it any way you want. Personally, the correct crossmember holds water to me, but because I do not like things hanging too low below my vehicles. Ground clearance means everything.

Agreed. This is a touchy subject any way you go about it

It will never be a good time to get an np249. Those grenade all the time in zj's, and people always swap them for np242s. And you actually should be looking at a different length rear driveshaft and front driveshaft that will need to be made or acquired. They are both different. Different length of transmission means different driveshaft lengths. Now, the length difference isn't much so you can get away with leaving it alone, but I suggest rebuilding yours

Meant trans. Auto correct.

No, I do not. I am saying that tried and true fluid is what belongs in there. I don't care that motor oil will hold up to use in the gears. I care that the job is done right, and putting motor oil in the transfercase is akin to putting ATF in an engine. Sure, it may quiet it down, but is it doing it's job, or covering up something incorrect? It's too thin anyways.

Something is wrong if you have to smell gear oil often. I don't like the smell of most fluids, but it is something that must be tolerated. You can all obviously do what you wish. I go with tried and true, and by god I will never trust an automotive engineer. They are the reason I am in business.