Eagle

The AMC Model 20 in the XJ and MJ never had two-piece axle shafts.

You do realize that the Jeep catalytic converter is not a constriction, right? The exhaust front pipe is 2-1/2 inches, and the 2-1/2 inches carries through the cat. The connector between the cat and the muffler necks down to 2-1/4. It wouldn't have cost Jeep anything to keep it at 2-1/2 all the way to the tailpipe outlet, so there's a reason why they necked it down to 2-1/4.

It requires the same as any other diff -- buy new gears, buy new locker ==> install. It's a VERY heavy-duty axle, but heavy, and less ground clearance than a D44.

Considering that you can run 31s with NO lift, and that you don't seem to be planning any severe off-road use that will require extra ground clearance ... why are you even considering a SOA?

Yes, it will make a difference, and not for the good. Way back, when my '88 Cherokee 4.0L needed its first exhaust replacement, my brother was manager of a Speedy Muffler shop. So I took it to him, and he talked me into a 2-1/2-inch exhaust system and turbo muffler. BIG mistake. The 4.0L is a torque engine, and a larger exhaust hurts low-end torque while favoring high RPM power. The problem is, you're just not likely to be running a 4.0L consistently above 5,000 RPM. In my case, I could instantly feel the loss of torque and acceleration, but I have no way to document it. What was quantifiable, though, was that my gas mileage dropped instantly by at least 2 MPG under all operating conditions. Fortunately, the Speedy tailpipe and muffler didn't last more than a couple of years. Normally, I'm bummed when the exhaust system goes. This was the only time in my life I was actually hoping for the exhaust to die. When it did, I replaced it with an over-the-counter OEM spec 2-1/4" tailpipe and muffler from Auto Zone, and I regained my seat-of-pants perfomacne and my gas mileage.

Impossible. The differential is a percentage, so any difference increases proportionately to the speed. In other words, if the speedometer is off by 2 MPH at 30, it's off by 4 MPH at 60 and 6 MPH at 90.Not impossible, I don't mean to argue but I know for (edit: almost) a fact it's 7mph I don't know if something was messed up before but it's 7mph off I've driven by a radar sign and when my speedo says 55 it says 62. Now I realize there could be some error! So I did it again and it read the same! The radar could be off but who knows I would just be happy if it worked again! :) You can be off by 7 MPH when your speedo says 55. But that's the ONLY speed at which you'll be off by 7 MPH. When your speedo says 27-1/2, you'll be off by 3-1/2 MPH. It's a proportion, not a constant error.

Impossible. The differential is a percentage, so any difference increases proportionately to the speed. In other words, if the speedometer is off by 2 MPH at 30, it's off by 4 MPH at 60 and 6 MPH at 90.

So you're going to have between a 4" and 5" lift. You don't need a dropped pitman arm.

The ZJ pitman gives you about a 1-inch drop, not 4 inches. It also causes moderate bump steer. Generally not recommended. Why do you think you need a dropped pitman arm?

That'll buff right out. My brother's Nissan pickup broke like that. He found a shop that specializes in repairing such damage and had it stitched back together. It's probably stronger now than it was when it left the fatory.

You might consider a preemptive strike, and have him replace all the freeze plugs he can easily get access to while he's at it. There are several that are a major PITA to access, and maybe those are best left until it becomes necessary, but I think there are three or four on the driver's side of the engine block, and it might be worth considering replacing those.

They do not interchange. The 2.5L (I-4) uses the small bell housing bolt pattern from the GM 2.8L The 4.0L uses a larger bell housing, and a larger bolt pattern. There are bell housings to install either an AW4 or an AX-15 on a 2.5L, but they aren't easy to find.

I always prefer OEM Jeep rims over aftermarket. As for the Pacers, I don't think they are hubcentric -- if they were, they wouldn't fit Fords. I would hold onto the Moabs and sell the Pacers.

Those "round things" are freeze plugs. They are cast into the block, have a round hole, and are plugged with a cup-shaped brass insert. The purpose is both to provide relief during the casting process, and to allow a place for coolant to expand without cracking the block if it freezes. My guess is that 20+ years without regular coolant changes resulted in an acidic coolant that gradually ate away at a freeze plug (or three), and that the localized overheating resulting from no coolant circulation built up enough pressure to pop a freeze plug. If that's all it is, it's an easy fix: pop out the old one, clean up the hole a little, apply sealer to the perimeter lip of the new one, and gently tap it into place.

You "think" your 4.0L is a bad rebuild? Wouldn't it be wise to be certain before you go through the exercise of an engine swap? What makes you "think" your engine is a bad rebuild?

Correction -- should be around 750 RPM for a Renix 4.0L

More likely the headlight switch is bad. The dimmer function is handled by an old-fashioned rheostat built into the switch. Basically, the circuit includes a length of coiled resistance wire, and one contact is a "wiper" that slides along the length of the coil, thereby varying the resistance. With age, the resistance coil develops dead spots, and eventually may fail completely. Either remove the headlight switch and test it, or just buy a new one and install it.

It could be the neutral safety switch -- as has been suggested. When it won't crank, have you tried moving the shifter out of Park to Neutral?

No.

When you get the no crank condition, enlist someone else to turn the key and try to start it for you. Turn on the headlights. You watch the headlights -- if they go dim when your helper tries to crank the engine, the starter and solenoid are working and there just isn't enough power to make it turn over. If the headlights DON'T dim when the key is turned to START, the starter isn't engaging or drawing any power.

The name sounds vaguely familiar. Is that the company that split off from Aussie Locker?

Do you have a factory service manual covering the AW4? IIRC you can remove the fuse and use the shifter to control sifts manually, but you lose one-half of the 1st/2nd combo (don't recall which). I'm also wondering if your issue is the transmission not shifting, or the torque converter lock-up going haywire.

That doesn't sound intermittent to me.

What are you adding STP to -- 75W90, or 85W140? Those numbers refer to viscosity. STP (and the Lucas oil treatment) is a "viscosity index improver" -- which means it makes oil thicker and stickier. It wouldn't hurt to add something like STP to 75W90, but I think it would be a mistake with 85W140. Many years ago I had a friend who was heavily into drag racing. Somewhere along the way, he "discovered" STP. He threw a quart in at an oil change, and he felt that his engine ran smoother and had more power. So the next oil change he used TWO quarts of STP. Then he tried three, and blew the engine. Pulled the pan, and stuff in the crankcase was sort of like J-E-L-L-O. Too much viscosity is just as bad as not enough.

10-4 Forgot about that one.