Eagle

There are no 87-89-1/2 AX-15s. The BA 10/5 was the 5-speed tranny behind the 4.0L from 1987 through the first half of 1989. The AX-15 was a mid-year production change in the 1989 model run.

The VIN will tell you if it's a base model, Pioneer, Chief, etc. And that will tell you if the gauges were stock. The base model had idiot lights, the Pioneer and Chief had gauges (although the tachomoeter was an available option, not standard). The base model also had the black "station wagon" steering wheel, and the Pioneer and Chief had the 3-spoke sport wheel.

The same.

About as bad as any small pickup -- which means pretty bad. Some weight in the bed (forward of or directly over the rear axle) helps. A limited slip differential helps a lot.

The problem is that most sensors available are either variable-resistance senders rather than switches, or don't switch on and off at the correct temperature. Of course, if you're willing to settle for controlling the aux fan manually, with a switch on the dashboard, then there's no problem.

Either your MJ is not a base model, as you described it, or a previous owner did some upgrades. That's a Pioneer of Chief steering wheel and gauge cluster with optional tach, and the mirrors at the front corners of the vent windows were not standard on the base model.

You will need motor mounts for a 4.0L from an XJ or MJ.

Is it possible to buy a new radiator with a spot to mount the existing aux fan sensor? or to add one to an XJ radiator at a local radiator shop ? ? Somebody reported finding one with the bung. The ones I've seen (including the new style that the radiator shop got by accident when I ordered an old style radiator) did NOT have the bung. So I guess they exist, but I don't know where.

The hard part is finding a way to control the auxiliary fan, since the early system uses a sensor in the driver's side radiator tank to activate it.

Easy conversion. Put the front axle, transmission and transfer case from the donor XJ into your MJ. I'm not sure about drive shaft length -- the XJ drive shaft won't be long enough, and the MJ drive shaft might be too long so you may need to have it shortened. But the 2WD tranny has a long tailshaft, so there's a possibility the driveshaft might be okay. Save the XJ rear axle as a spare in case your D35 blow up. If nothing else, you'll have spare shafts and brake drums. BTW, the XJ Pioneer will have gauges instead of idiot lights, so you can swap the gauge cluster into your MJ, too. And the 3-spoke sport steering wheel. And the fancier "hockey stick" armrests. What does your MJ have for side-view mirrors?

The Metric Tonne package was available only on the longbed. Not sure, but I think a tow package was available on the shortbed. And I think the Eliminator was available only as a SWB.

It;s difficult to find a used pickup that even runs for under $5,000. How much do you have in your MJ,a nd how much will a junkyard 4.0L cost? Then factor in that insurance is possibly cheaper on a 20-year old truck, and taxes are certainly less than on a new truck. I'd fix it. Good excuse to go for the whole drive train from a donor and convert to 4WD.

Are you asking about a front skid plate, a transfer case skid plate, or a gas tank skid plate? And what "rod" are you referring to?

I have two or three heater blowers riding in the back of the XJ that died with their boots on. The one that's in the XJ now is nearing the last round-up, too -- lots of squeal when it first starts spiining on cold mornings. Apparently it's possible to buy just a replacement motor for these things, but ... how do you get the blower impeller off the motor shaft without breaking it into ten zillion little pieces? Has anyone done this -- successfully?

??? What different fans? You asked about the OEM auxiliary fan. We've reported that it WILL work, but your truck doesn't have the wiring harness for it so you will have to install or create a wiring harness for it. If you want to use an aftermarket fan, you'll have to do the same thing.

That's another point. I assume the ZJ bar was swapped in because it's larger in diameter. Which bushings did you use? If you used the original MJ bushings with a fatter ZJ sway bar, the bar can't rotate like it's supposed to and that could explain why the suspension feels bumpier.

There is no reason in the world why 3/4" lift spacers, which on an old truck probably barely returned it to stock height, should require 2-inch or even 1-inch longer sway bar links. More likely, the sway bar is rusty and is binding up in the bushings. I would remove the sway bar, clean and sand it smooth where it rides in the bushings, paint it, spray silicone on the bushings, and reinstall.

Flint54's explanation of how it works is pretty good. The reason for it is that a pickup without a load has very little weight over the rear axle, so it's easy to have the rear brakes lock up before the fronts. The height-sensing valve is intended to alleviate this, while adjusting the rear brakes to provide more braking when the bed is loaded. And, if properly adjusted, it does that very well. I am only partially in flint's group A. I don't regard the height-sensing valve as absolutely necessary, but I do regard it as a good thing. I am, however, in flint's group B. I have personally experienced a potentially catastrophic failure of a rear height-sensing valve. I had to make a panic stop, and the valve simply exploded. The result, of course, was NO rear brakes. So I don't trust them. If they were available (and not overly expensive) I would replace it. But they have not been available for many years. Personally, I am comfortable driving without one. It must be recognized that, under some conditions, the rear wheels WILL lock up prematurely with no proportioning to the rear wheels. I grew up long before such devices were offered, so this doesn't bother me. For those who aren't accustomed to dealing with rear brakes that lock up before the fronts (which can cause oversteer and spin-outs), I recommend removing the height sensing valve and installing a Wilwood (or Mopar, which is probably the same thing) adjustable proportioning valve in the rear brake circuit. It can be set to properly limit the rear brake force when empty, and then allow more rear brake force when loaded. The downside is that it's not automatic -- you have to experiment, find the right settings for your truck, and remember to turn the knob when you load or unload your truck.

They all did when they left the factory. I know of one 1988 red Chief that doesn't have one now ... and I know of two others that won't have it when they get running and registered.

You can use an OEM electric fan, but regardless of whether you use the old style (which I think is no longer available) or the new style, it is NOT plug-and-play if your truck was not originally equipped with one. The sensor screws into a bung in the driver's side radiator tank, so you'll need that sensor. That sensor, in turn, feeds a relay that mounts to the driver's side inner fender, near the air box. And then the relay sends power to the fan. If your truck doesn't have the fan, I'm 98.7% certain the wiring isn't there.

Maybe less. They were about $12 per PAIR when I bought them, but I'm sure they've gone up. But that's per pair. When I ordered mine, after seeing 4x4 vendors getting $40 and up for so-so perches, I heard "$12" from the parts guru and I had to ask, "That's for one, right?" He said, "I don't know, that's the price for the part number you gave me." (I had the number from the printed Mopar Performance catalog, but the catalog didn't specify if it was one or a pair.) So I had him order two. When they came in, the boxes clanked. So we opened one box -- and out came two perches. Best deal in history, beyond a doubt.

You still have to open a front caliper and blow the pressure off the front circuit so the shuttle valve will open the by-pass circuit to the rear. Otherwise, the pressure bleeder can't push fluid through the second line.

Buy the Mopar perches. They are HEAVY duty, and you can't possibly justify wasting the time to make your own given how cheap the Mopar parts are.

If you look at the photo of the cut-away front distribution block, the bypass port is blocked by the shuttle. You can open rear lines and let it drain by gravity for a week, but there won't be anything flowing (or dripping) through the bypass circuit. That be the problem.

Well, here's the thing about that -- I don't know how the height-sensing valve relates to the bypass circuit under normal conditions, so it's possible that your brakes work fine normally, but if you were to lose the fronts you might not have any rears. What's supposed to happen is that normal operation routes brake fluid from the master cylinder to/through the rear proportioning valve. But if you're running with no load so the valve is allowing very little force to the rears, if you lose pressure to the front circuit you're then stuck with maybe 10 percent braking power. So, those clever engineers engineered a bypass circuit that's activated by the shuttle valve in the master cylinder. If you lose pressure to the front circuit, the shuttle valve (in addition to triggering the "You got no brakes, Dummy!" light) opens the port to the bypass port. That sends brake fluid past the rear height sensing valve and directly to the rear axle, so you get the full benefit of however much braking your rear wheels can produce. However -- if there's air trapped in the bypass circuit, activating will NOT send full force to the rear wheels, because the air will compress and negate the bypass circuit. As I said, I'm not 100 percent certain just what the rear valve does internally, but I am of the opinion that good rear brakes under normal conditions does not provide any evidence that the bypass will function as advertised if there's a problem.