AZJeff

Those look to be some sort of doubler used to tie to sections of the "frame" rail together. It would say having a piece in that area that performs that function is probably structurally critical. If you are worried about the area between those doublers and the bottom of the "frame" rail, you can do a few things: 1. try to etch the area between the two pieces with some sort of acid to remove any existing rust. Then THOROUGHLY neutralize the acid and allow it to dry. Then apply POR15 into the joint to allow that specialized paint to convert the remaining rust into a neutral state. 2. cut ONLY the bottom surface of the frame rail off, and clean the bottom of those doublers of any rust. Then weld on new steel of at least the same guage or heavier on the outside. You can also go in and weld those doublers to the new bottom surface of the frame rail from the inside. You might need to make some holes in those doublers before installing the new bottom of the frame rail, and then do some plug welds between the doublers and the new bottom surface. 3. remove the existing doublers from inside the "frame" rail, and clean the floor of the frame rail in the area you say cannot be reached now. Then make new doublers from appropriate guage metal, and weld them into the frame rails inside. Whatever approach you choose, don't just remove those doublers and call it a day. Those are pretty important in that area.

How large are the braces you are running from the rock rails to the "frame" rail? If they are 2" square tube or bigger, those can replace the torque boxes, provided you actually tie those braces not only to the frame rail, but to the floorpan as well. The torque boxes are intended to tie the rocker panel area of the cab to the "frame" rails. Your braces would accomplish the same thing, as long as they are big enough and located in a similar position along the length of the "Frame" rail.

What e-fan(s) do you use in your 3-fan setup? Where do you sense the 180* temp versus the 210* temp? Curious as to how you approached this, and I might try to duplicate your scheme.

The material depends on the plastic part in question. PVC is used on pieces that need to have some flexure to them for installation and removal. Door kick plates, trim around the bottom of the door, etc. Pieces that are more "permanent" in their position (such as the glove compartment door and the like) are something else, most likely a polycarbonate/ABS blend. Manufacturers tend to mark the part on the back side near the area where the part number is molded in with an abbreviation for the molding resin used. Since all the trim is out of my MJ right now, and knowing about these markings, I looked some pieces from my vehicle. to see what material markings the have. The answer was NO material markings, exceept for the ones from the dash, and those are marked PC/ABS. Unfortunately, my dash/instrument panel is from a 2000XJ, so that doesn't help tell you what was used on an original MJ dash. I would say it's a safe bet that most of the "hard" plastic in the vehicle is PC/ABS or straight ABS.

Air shocks?

I put a "plastic gas tank from a Dodge" in my SWB MJ, and the tank sticks down below the "frame" rails less than 1 inch at it's lowest point. Since I have a 4" lift already, that protrusion is not very much. FWIW......

Dumb question: If you apply vaccum to the system where it enters the passenger compartment, does it HOLD vacuum, or drop instantly?

I agree with Eagle. The instrument panel Voltmeter in most vehicles, particularly the older stuff like an MJ, are considered "trend indicators" at best. In other words, they are NO WHERE near accurate enough to indicate anything more than if the system is charging or discharging the battery, and that is done by observation and experience of the guage reader (aka, you, the driver). I suppose one could go crazy and attempt to "recalibrate" the guage on a workbench outside the vehicle. However, there is no guarantee that process wouldn't break the gauge completely, so it's a risky proposition. If it was me, I would learn to live with it. PS....Eagle's assumption that the gauge has a linear sweep is up for contention. Those older instruments tended to be very NON-linear.

Wow. I learned something new about a pretty old-tech device. I never encounter that in my 50+ years of working on cars.

NICE!!!

OK, I must be a dumbass. What is an "inertial ring"?

I am still new to MJ's, and had no idea that a D44 is an oddity in a SWB MJ. My 1989 MJ (which is a Franken-MJ to begin with), I have a D44 in the back, and it's SWB. It does NOT look like the axle tubes have been cut/welded upon. So am I to assume that the axle on my Comanche is from a LWB MJ?

The door sill is part of the rocker panel stamping, if I recall. (At least at the factory that is the case.) Do aftermarket replacement rocker panels for an XJ include that part of the stamping?

I disagree with that assessment. If a junkyard has pulled a trans and placed it in an enclosed area (no rain or dust storms), if the trans was working when pulled, it will be a FINE candidate for installation into another vehicle. The internal parts will not corrode/rust/deteriorate if they were coated in ATF at the time of removal. The rear and front seals might be dried out and needing replacing, but that is not big deal. A new pan gasket and filter screen would be prudent anyhow. Once that is done, that AW-4 would be ready for transplant.

As a retired mechanical engineer, I agree with Eagle. A "box section" (which is the technical term for the added piece we see in MJ floorpans) is not a part intended to improve crashworthiness. It's intended to increase the stiffness of the "frame" to longitudinal bending loads. Most of us probably rarely, if ever, tax our MJ's to the published limits from AMC/Jeep/Chrysler. Removing this relatively small "hat section" from the top of the floorpan will have minimal impact to the overall structure, particularly in a vehicle that spends all it's time driving on streets empty or at best lightly loaded. SIde note---as an automobile afficianado for 50 years, that "hat section" welded to the top of the floorpan is one of the STUPIDIST design features I have ever seen. It TRAPS WATER (and other stuff) almost by design, and invites corrosion. It is almost by design intended to destroy itself. Knowning how engineering is often done, I suspect the addition of the hat section was an "eleventh hour" modification to the design to improve the basic Cherokee "frame" stiffness without forcing a major redesign of the lower "frame rails" that the MJ shares in common with the XJ. In other words, it was a "band-aid" to make the MJ more rugged without impacting the XJ's common parts. I wouldn't worry one bit about taking them out, unless you are making a rock crawler, in which case you are doing other stuff to the chassis already.

My error in passing out this information. I now see that my MJ has an XJ prop. valve in it (from a previous owner), and I assumed all MJ's had that valve as well. SOrry to anyone I led astray. Eagle's information is to be followed, not mine.

THAT TOO!!

The proportioning valve also contains two features mandated by Federal motor vehicle safety laws: 1. a design that separates the front and rear brake systems so that one system can be open (leaking) and leave the other system capable of providing braking function. This is accomplished by having a separate piston and output for the front and rear brake systems in the MC, and they are routed to the prop. valve and theron to the wheels. 2. an electrical switch on the prop. valve that will close to turn on a light on the dash when one of the two systems develops a leak that causes an imbalance in pressure from front to back. The prop. valve also will restrict/reduce pressure to the rear brakes to prevent premature locking of the brakes due to excessive line pressure to the back. It does this with a spring and and O-ring inside the valve, and is normally NOT adjustable. The fact that you are opening the fronts and getting them to virtually shut off makes me think your prop. valve is defective. Either it's gunked up, or missing it's O-ring, or missing it's spring.

There is also a trim cement made by 3M that can be used to attach some moldings. Most auto parts stores that carry body repair stuff will have it. It works well on pieces of trim that are lack openings or irregular shapes in them. Things like letters spellinig a word (J E E P, for example) don't do well with this stuff, but if you are attaching something like "4.0 Litre", then it works perfect.

You wind the award for this year for finding the most hillbilly auto repair done by a previous owner!!

I am a firm believer in doing both when I see one that is worn. I do this on brake calipers, wheel bearings, shocks, springs, and any similar "paired" items. Besides, Amazon only had the carrier bearings as sets of 2 anyhow, so I will do both.

Thanks, Eagle. I did some searching on the interweb, and found that, as long as the carrier is going into the same housing from which it came, the chances are good that all would be well with new bearings. Let's hope it turns out to be true!

While putting new axle seals in the front of my MJ, I discovered that one of the carrier bearings is toast and is going to need to be replaced. Here is my question: If I replace the bearing/outer race, what are the chances that the preload and backlash will be within the original factory spec.? I am hoping I can just remove the old bearing, install a new one (using the same shim stack) and be within desired specs. Am I being unrealistic?

Motor mounds and transmission mounts have nothing to do with death wobble. In fact, bad motor mounts can be diagnosed really easily with the vehicle sitting still and having a helper "load" the engine with the transmission in gear (and the parking brake or service brake applied FIRMLY). While the helper is doing this, you are examining the motor mounts for severe distortion of the cross bolt in the rubber. It should move some, but NOT to the point where it reaches the outer part of the mount. I suspect you still have a front suspension issue if you are experiencing TRUE death wobble. Your description of a pothole or a "wave in the road" triggering the behavior is CLASSIC death wobble symptoms.

My address is in the area that requires an emissions test. If I lived 2 miles east of here, I would be exempt. Since I am not roadworthy right now without brakes, I am not too concerned yet. I will probably take it in and have it tested with just the front two California cats, and see if it passes. I will also investigate the exemption mentioned in the link by "Ohm" Standby for more details later.