Eagle

Is your current daily driver 2WD or 4WD? If it's 2WD and you're happy with it, then you don't need to convert the MJ to 4WD. If your current daily driver is 4WD and you'll miss it, then convert. FWIW, I put a Truetrac gear-driven limited slip differential in the rear axle of my '88 MJ. I live in Connecticut, we get snow and ice, and there's a steep hill at the end of my road. With the Truetrac, I almost never had to use 4WD on the street -- I had 4WD for off-roading. If I had carried a bed box with a hundred pounds of mason's sand in it during the winter, I absolutely would not have needed 4WD during the winter.

^^^ This. There must be some agency in your state that licenses automotive repair facilities. I would file a complaint with that agency. Also, since Chevrolet was directly involved (the cold contact from On Star), I would also file a formal complaint with whatever federal agency has oversight of automotive manufacturers ((FTC?). And have your GF contact her U.S. representative and ask the Congresscritter to also follow up with whatever federal agency regulates car manufacturers.

And, IIRC, the BA 10/5 also used the 21-spline transfer case. There's also a change in the pitch of the input shaft gear somewhere along the way, so you can't even assume that you can just swap the input shaft.

The year does matter, because Jeep changed the spine count somewhere around 1989 or 1990.

I think you misspelled "feces"

Virginia -- long bed, or short bed?

Subrogation

I was about to offer this suggestion.

No, it won't. There have been far too many documented cases of members here who had low or no oil pressure that was entirely fixed by throwing away their Fram oil filter for there to be any reason whatsoever to use a Fram filter on a Jeep engine. DON'T ... DO ... IT.

What did you fill it with?

Illumination has nothing to do with the sender. What year is the "new" cluster out of? The early ("Type 1") clusters, which this appears to be, did not return the gauges to zero when the ignition was shut off -- they stayed wherever they were at that moment. Try turning the ignition off. Take the wire off the sending unit and connect it to a good ground using a jumper cable (or a helper). Then turn on the key and see what the gauge says. Repeat with the wire unplugged and not touching anything. Report results.

Also check the O2 sensor, but I'd look first at the TPS.

Does the TBI have a throttle position sensor? I imagine it must -- I'd start by checking that. What happens if you leave it in neutral and try to rev the engine?

In other words, he doesn't want to sell it.

Doesn't work for the 61-amp models. The early XJs and MJs use Delco internally-regulated alternators. Those came in two frame sizes. I don't remember where the cutoff was, but the 61 and 74 amp alternators are definitely the smaller frame. I needed an alternator for my '87 MJ 4.0L. I took it to the local rebuilder guru, who initially assured me that he could upgrade it to 125 amps or something like that. When I went to pick it up he announced that he wasn't able to upgrade it because my old one was the small frame, and to get the upgrade would require a large frame. If you want to keep things simple, get the 74-amp from the parts store. You can buy a larger one by looking up alternators for 4.0L XJs with a/c, but then you may run into having to modify brackets.

Carburetors are easy to tune and easy to replace. I would say, "Go for it," but $1200 is a ridiculous price for an '84 XJ. $500 would be my absolute top.

^^^ This. There are some people who feel the CAD housing mount for the upper control arm is sturdier than the sheet metal bracket they used on the non-CAD axles. I don't disagree. I'm not going to swap an older CAD axle into my 2000 XJ, but the MJs and the old XJ are just going to have the CAD locked in the engaged position, and go forward from there. The problem with keeping a working CAD is that it's not a question of "if" it will fail, at's a question of "when" it will fail. And it always fails when you need it. Been there, done that.

There's leather, and then there's leather ... and then there's leather. It used to be when we saw something that was made of leather we could expect that it was made from a section of the hide from a cow, bull, horse, or sheep. Then they came along with "bonded leather." That's essentially the leather equivalent of particle board -- they take all the leather scraps and dust left over from making things out of real leather, grind it into a powder, mix it up in some sort of glue, and make sheets of so-called "bonded leather." Some of it isn't too bad, some of it is truly awful. And then there's stuff that's made of ( and I've seen ads that literally say this) "genuine imitation leather." Is that generic Naugahyde, or is that bonded leather? I don't have a clue. But bonded leather gets to be sold as leather, and it doesn't even have to be declared as "bonded" leather. It has leather products in it, so it's good to go as far as the FTC is concerned (insofar as I have been able to determine).

When the problem with sulpher-bearing additives in GL-4 and GL-5 gear oils eating the synchros in the AX-5 and AX-5 transmissions became known, the factory recommendation changed to 10W30 motor oil. The parts guys at my dealership showed me the notification, many years ago.

Nope. Sounds like a solid plan. I have a TrueTrac in the Dana 35 under my red '88 MJ and I think it's "the bee's knees" (whatever that was supposed to mean). One other point: in your opening post you wrote that you don't have the height sensing valve "for this axle." The height sensing valve is mounted to the frame and it isn't axle-specific. Since you're converting to disc brakes, you should probably look into making the connecting rod for the height sensing valve adjustable, and that will allow you to dial in your rear brake bias with the discs.

M.R. 277 is a factory-published compilation of I.S. [Information Service] Notes in a book that's the same dimensions as the FSM, but it's only 5/8" (16mm) thick.

Yes, I can. But it doesn't come from the FSM, it comes from M.R. 277 for the Comanche, I.S. Notes. Specifically, it's in I.S. 14E, which addresses spring identification and selection. For front ride height: For rear ride height: Stuck into my copy of M.R. 277 I also have a single photocopied page with the comparable information for the XJ, but I don't remember where I found it. For the XJ, there is no distinction between 2WD and 4WD. The front dimension is 6 3/4" (17 cm). The rear dimension is 6" (15cm). Both are plus-or-minus 1/2 inch.

Reading comprehension is everything. Back to remedial reading 101

Factory rear spring U-bolts were 12mm for the XJ and 14mm for the MJ. 14mm is roughly 9/16"

Except that the Cherokee rear drive shaft is too short, so you'll have to either have a driveshaft made, or have a driveshaft modified.