Eagle

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.

What size dock washer, and what size bolt? "2 1/2 inch" is not a size, it's a length.

Isn't the Jeep 4.7L a hemi engine? But I don't know if the 4.7L would fit in an MJ -- and having owned a WJ with the 4.7L, I hope I never ever own a second one. Stroker ...

Much cheaper than any V8 conversion would be a cam and a set of sightly larger injectors. http://comancheclub.com/topic/17726-drag-comanche/ https://www.allpar.com/trucks/jeep/comanche.html

Yes.

Then what's the coolant temperature sensor on the left side of the block for?

Sylvania Xtravision are not "high dollar" replacements. They are the same power as stock on high beam, but more power on low beam, and they have a better distribution. When I bought a used 2001 XJ the factory headlights were like two piss holes in the snow. I replaced them with a pair of Xtravisions and those give me all the light I need. Plus they are rated for something like twice the life of OEM, and abut four times the life of the Silverstars.

This is very interesting, considering that there was no shortbed Comanche in the 1986 model year. The shortbed first appeared in 1987. Fuzzy recollection is that the 1986 16-gallon tank is the same size as the larger longbed tank, with an internal restrictor to limit capacity.

The cross-over point is approximately 165 degrees. But that's approximate. You can probably get by with a 180 degree thermostst, but the engine was designed to run with a 195. I can't think of a single valid reason to NOT run what the factory has determined through extensive testing to be the best choice.

Unless he gets an axle that doesn't include calipers, and then tries to use his existing calipers.

Don't forget the hubs/brakes compatibility issue.