Eagle

So he wants to retain both hard lines, eliminate the rear height sensing valve, and merge the two hard lines just upstream of the rear flex hose? The problem is going to be bleeding. If there's any air in the bypass (emergency fail-safe) hard line, stepping on the brake peddle will just allow the fluid in the primary line to back-feed and compress the air in the secondary line rather than actuate the brakes. It is possible that tripping a fail in the front brake circuit, per the factory procedure for bleeding the rears when you do have the height sensing valve, might do the job. But ... I don't know if the height sensing valve has a backflow preventer (I would guess it would have to), so I don't know if this would work. Overall, I think this sounds like a really foolish thing to do. Instead of exposing ten feet of steel line to rust and corrosion, let's expose twenty feet of steel line to rust and corrosion to get to the same place. What could possibly go wrong?

No, if you do it as the diagram indicates, it's the bypass (emergency) line that gets removed and the port for it gets blocked at the metering block in front. The "failsafe" circuit no longer exists, and the line to the rear operates the rear brakes normall (with no proportioning) -- just like the cars I grew up with.

If the hoses leading to and from the heater core don't get hot with the vaccuum valve open and the engine at normal operating temperature, the only answer is that there's no coolant flowing through the heater core. Let's face it, it's 24 years old and probably plugged solid. I kept the heater core on my '88 Cherokee flushed out, and it sprung a leak three years ago. I just blocked it off and ran without a heater for one winter, then I replaced the heater core.

A colder thermostat will NOT help. If you're running warmer than usual, the thermostat is open and the radiator can't shed the heat fast enough. Open is open -- opening earlier won't alleviate the problem. Do you have an automatic? If so, do you have an external transmission cooler? How old is your radiator? Have you had it boiled out and flow tested?

Check the routing of the speedo cable. If there are any tight bends, try to move clips or something to change the bends to a larger radius. If you feel up to it, remove the instrument cluster and take the speedo cable off the speedo head. You should be able to pull the cable up from there to remove it from the outer sheath. (NOTE: Before doing this, inspect the entire length of the cable. If the outer sheath is frayed or broken, do NOT pull the inner core out or it may not go back.) If you can get the inner core free, wipe it down with a rag wetted with mineral spirits to clean off old, dried lubricant, then lubricate it with fresh, clean lube. I think there are special lubes made for speedo cable, but white lithium would be a lot better than 20+ year old, dried-out whatever. Then push the cable back into the sheath, being sure it engages the drive gear socket, reattach to the speedo head, and replace the instrument cluster.

Be VERY careful changing that bulb. It's like a micro-mini version of the bulbs for the gauge cluster -- the bulb itself is like a tiny version of an old flashbulb, with a glass base and two exposed wires that snaps into the socket. The socket itself is a quarter turn bayonet mount into the panel. The ears on that little socket are VERY fragile. Be gentle or at least one of them will snap off.

Hmmm ... Which fuse panel, the one under the hood or the one behind the passenger kick panel?

More problems with the "new" (to me) 2001 XJ. After driving for more than about a half hour or 45 minutes, the radio light blacks out. If the radio isn't turned on, that means I lose the clock. Even with the radio or CD playing, the dial goes totally black. There's no discussion that I can find on radio dial illumination in the 2000 XJ FSM. Does anyone know if this is a simple bulb replacement, or is the only "fix" going to require replacing the radio?

For the Dana 30 with CAD, on the driver's side the seal is inside the diff housing. I assume that would be considered "inner." The passenger side does NOT have a seal in the diff housing, because the gear oil also lubes the sliding spline at the disconnect. The seal on the passenger side goes outboard of the disconnect. I can see how that might be called "outer." There is only one seal on each side.

My first thought, too. Been there, done that. Didn't even get a tee shirt.

Comanche and Cherokee use the same sensors, but the senders for oil pressure and coolant temperature with idiot lights are simple ON/OFF switches, and the senders for gauges are variable resistors. You can use the senders from the donor vehicle, or you can go to Auto Zone and order the sensors for use with gauges.

DOH! I did actually. Seemed like a good idea at the time haha But I tried grounding the wire to the block, as well as unplugging it and noticed no change in the gauge reading. Well, there's your clue. The sender range is 0 (zero) to 88 ohms. The classic test for a non-functioning gauge is to unplug the wire from the sender. With the ignition on, this creates an open circuit (infinite resistance), which should peg the gauge all the way to the right. Then ground the wire to a known good ground on the engine. This creates a short circuit, or zero resistance. The needle should then peg all the way to the left. If you do this and the gauge doesn't move, either the gauge is faulty (which you can check by removing it and repeating the est using jumper wires) or there's an open or shorted wire between the sender and the gauge cluster.

Is there an OME shock listed for the ZJ? I believe the ZJ rear shocks are longer than the XJ and might be right for an MJ at stock height.

My '88 XJ Pioneer has a tachometer. A lot of them do -- it was a factory option. Yes, the tach should function. The wiring is all there -- it's plug-n-play.

Considering that the MPFI conversion kit Jeep used to sell for the 4.2L carbureted Wranglers was nothing but the engine room harness from a '94 4.0L with MPFI, my guess would be that the dash harness is going to be okay. Why would they make two different dash harnesses for the same vehicle? The tach should have a potentiometer on the back to adjust between 4-cylinder and 6-cylinder.

'88 XJ, 4.0L 5-speed, stock gears and 225/75R15 tires I typically get around 19 in local driving and 20 to 22 highway. '88 MJ, 4.0L 5-speed with 3.73 gears and 31x10.50-15 tires, about 17 in local driving and 19 MPG highway.

The axle itself will bolt right in. Just pop the draglink loose at the pitman arm, pop the track bar, and move everything over. The control arms are the same for all years of the XJ and MJ, so you can either leave them in the vehicles, or move them with the axle. I'm not certain, but I DON'T think the calipers are the same. I think you'll have to use the 2WD calipers on the 2WD axle. Jeep changed the calipers beginning with 1990.

Not true. There's an efficiency point that moves around depending on load and a few other variables. Usually it's significantly below peak torque. Best mpg I've ever had was cruising at around 1800 rpm. If I go much faster, my fuel economy makes a steep downward curve. onlyinajeep726, where did you get that list and what exactly are the numbers? As in where do they come from / how were they determined? For the engine, the torque peak RPM is absolutely the most efficient operating speed. Torque is mundanely defined as "horsepower per revolution." so the engine speed that produces the most power per revolution is the most efficient engine speed. In a vehicle, of course, outside forces come into play. Most importantly, aerodynamic drag and parasitic losses due to friction increase exponentially with vehicle speed, so there is a point where the direct correlation breaks down. I'll get to that in a minute. I have experimented with this mostly with the '88 Cherokee, which is a 4.0L 5-speed. I live in Connecticut, where most of the highways still have 55 MPH speed limits, and a couple of stretches of interstate allow 65. I only use 5th gear on the highway -- 55 MPH in 5th gear is only 1540 RPM, and 65 MPH is only 1820 RPM. Below 55 MPH, 5th gear is totally useless with the 3.07 gears. I have on several occasions driven the same route in 5th gear and then again using only 4th gear, and every time the gas mileage is equal or better using only 4th gear. Using 4th as the cruising gear, 55 MPH is at 2055 RPM and 65 MPH is at 2430 RPM. So in 4th gear, 60 MPH is sitting right on the torque peak, and delivers the best gas mileage. I had another proof of this a number of years earlier. When I was in the Army, I drove a Rambler American, with an earlier version of the engine that became the 4.0L Jeep engine. That car was a 3-speed manual with 3.07 axle gears. The gearing worked out such that 2500 RPM was exactly 60 MPH. Running at that speed, I got 28 MPG -- the dealer asked me to never mention that in front of other customers, because they'd all complain that their Rambler wasn't doing as well. A 6-cylinder Rambler American wasn't exactly a race car, but I wanted to optimize the performance. I pt on a straight-thru glass-pack muffler, tweaked the ignition timing (we could set it, in those days), and made up a home-brewed open air cleaner to replace the fully-enclosed can that was standard from the factory. I took it out on I-95 near Edgewood Arsenal, MD, late at night to test my tweaks. I finally broke 100 MPH -- got it up to (IIRC) an honest 104 MPH, after correcting for speedometer error. Then came Winter. I needed snow tires, and I couldn't afford them. My brother had switched from bias-ply tires to Michelin radials, so he gave me his snow tires. They were from a larger, heavier car and were probably four sizes larger than my tires. But they fit inside the wheelwells, so I used them. One night I took the car back out on I-95 with the snow tires on to check the top speed. It dropped, from 104 to 80. Why? Because the larger tires reduced the effective final drive ratio enough that the drag curve crossed the power curve, and above 80 MPH (which should have been 3333 RPM but dropped well below that with the bigger tires) there just wasn't enough horsepower available to overcome the aerodynamic drag and parasitic losses above that speed.

I would try the Pennszoil Synchromesh transmission fluid. I have heard good reports on how it performs in the Jeep transmissions, even though it wasn't formulated specifically for them.

2250 RPM, for any gear. The most efficient engine speed is the torque peak.

The dealership CAN order them. They are in the Mopar Performance catalog, and I have posted the part number several times in the past. They are by FAR the best deal going. The Mopar part sells for about one-third what anybody else gets, they come as a pair (when you see the price, you'll be sure it's only for one perch), and they are MUCH heavier-duty than the perches on the stock axles. That's because they are made for building heavy-duty axles in race cars that put a lot of torque to the ground. Found it:

NO! If you do this, the steering wheel will be off-center when the steering box is straight, and when the steering wheel is straight the steering box won't be. DO NOT DO THIS -- IT'S WRONG.

You can resurface the 2.5L flywheel, but if you're on a tight budget why do it? Buy a Scothbrite pad, chuck it into your electric drill, and buff away the rust.

What you're overlooking is that in 1988 they offered high RATE (meaning higher capacity) springs that did not increase the ride height. I made the mistake of ordering my 1988 Cherokee with the optional, heavy-duty (not "off-road") suspension. It rides at the stock height -- 17-1/2" front / 17" rear. But it rides like a ... well, like a truck. And after 25 years and 287,000 miles, including hauling some VERY heavy loads, it hasn't sagged even a fraction of an inch. Those are a different animal from the later model XJ "Up Country" springs, which were part of the off-road package and were intended to increase the ride height by an inch compared to the standard suspension.

Actually, factory ZJ V8 springs generally lift an XJ or MJ exactly one inch. But, as you can see from Hornbrod's list, they are not all the same. In fact, at times Jeep would put different number springs on each side to level out the ride height depending on options in the vehicle. I ordered what is now my wife's 2000 XJ Classic from the factory with the Up Country suspension. That rides 1 inch higher than "stock." Before I had the chassis rustproofed, I crawled under and read the codes off the springs, then I ordered a pair for use in my '87 MJ. When I have the spring number to the guru at the parts department, his immediate response was, 'I though you only had XJs and MJs - why are you buying a pair of ZJ coils?" I subsequently picked up a used 2001 XJ without the Up Country suspension. I bought another pair of the Up Country (ZJ V8) coils) and threw them into that. I measured both sides, before and after the installation. They lifted the front exactly one inch.