Eagle

Agreed. The first number in an oil designation is the cold viscosity, the second number is the operating temperature viscosity. So a 5W50 is thin like a 5-weight when cold, but still has the viscosity of a 50-weight when hot. Like Noriyori, I run 5W50 (I use Castrol Syntec) in the high mileage engines to compensate for loss of oil pressure due to worn bearings.

As I commented above, the 1988 FSM shows an optional 17:1 fixed ratio power steering box that was included in the off-road package. I don't know what year that option was discontinued. The 1994 FSM shows power steering boxes in 14:1 and 12.7:1 fixed ratios, plus a 13-17:1 variable ratio. BUT ... the 1994 FSM covers more vehicles than just the XJ, and the book doesn't tell which vehicles or models were equipped with which box. There are 2-letter codes for each, stamped into the top of the box. My guess would be that the short wheelbase Wrangler got the variable ratio, so the steering wouldn't be as "twitchy" over center on the highway. The 2000 XJ FSM shows only the 14:1 fixed ratio box. {EDIT TO ADD} I did a bit of research through the parts manuals. Let's just say that it's a bit more complicated than "There's only one box for all the years." 1988-1990 XJ/MJ parts manual: XJ/MJ Part No. 5200 2737 1991-1993 parts manual: . . . XJ/MJ Part No. 5203 8002 . . . . . . . . . . . . . . . . . . . . . . . . .ZJ . .Part No. 5208 7753 or . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5208 7754 . . . . . . . . . . . . . . . . . . . . . . . . .YJ . .Part No. 5203 8003 1994-1996 parts manual: . . . . YJ . .Part No. 5203 8003 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 5203 8002 ... '94 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 5203 8408 ... '95 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 5208 8015 ... '96 . . . . . . . . . . . . . . . . . . . . . . . . .ZJ . . . . . . . . 4 different boxes listed, depending on options 1997-1999 parts manual: . . . . XJ . . . . . . . . 5208 8386 ... '97 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 52088 386AB ... '98 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 5208 8532 ... '98 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 52088 386AD ... '99 . . . . . . . . . . . . . . . . . . . . . . . . .XJ . . . . . . . . 52088 532AH ... '99 2000 XJ Parts Manual: . . . . . . XJ . .Part No. 52088 386AC 2001 XJ Parts Manual: . . . . . . XJ . .Part No. 52088 386AC No ratios listed, other than a couple in the export listings (which I didn't try to reproduce)

For 1988 the factory recommendation was 10W30 or 10W40. When my '88 was new I ran 10W30 in the winter and 10W40 in the summer. It does not sound like your engine was "rebuilt. There's a lot more to a rebuild than replacing gaskets -- like bearings, rings, valve job, etc. So basically you have 118,000 miles on the engine. AND ... remember that the 2.5L has more gear, so for every mile you drive, the engine spins around more times than a 4.0L would. You have a 5-speed, so your gears are 4.10s. My '88 4.0L 5-speed has 3.07 gears. In round numbers, your engine goes around 4 times for every 3 times mine goes around. So, since most of us use the 4.0L as the frame of reference, your rings and bearings have seen the equivalent of 157,000 miles. I think you should be running 10W40 as a minimum. If it were mine, I'd be running 20W50 for the summer, 10W40 for the winter. New London must be in a micro climate. I'm outside New Haven -- we had several nights this past winter that were -10 without factoring "wind chill."

I got it from the factory service manual. I checked the 1988, 1994, and 2000 FSMs. [Note that the very early XJs had a 17:1 fixed (not variable) option as part of the off-road package. I've never encountered one -- ever.] The only way for me to "show" you would be to scan or photograph the page, upload it to Photobucket, and then post a link to the image. I don't have time for that. You can either accept my word that's what it says ... or not.

Just to be clear -- you are "all right," but you're not "fine." Your idle pressure is below spec. That's to be expected on an old, probably high mileage engine, but the reason we expect it is that we expect moving parts to wear. While the minimum idle oil pressure is 13 psi, most healthy Jeep engines idle at around 20 to 25 psi. So you have some early warning signs -- IMHO you should start considering either dropping the pan and replacing the main bearings (or all the bearings, while you're in there), or start looking for a spare engine you can rebuild while the one you have still runs. As others have commented, oil weight also matters. When my '88 went over 200,000 miles and the oil pressure started reading a bit lower than what it had been, I switched to Mobil-1 full synthetic in 15W50 weight, then I went over to Castrol 5W50. My oil pressure in the '88 still isn't where it was when new, but I'm now at 287,000 miles and I'm still within factory specs.

The stock XJ/MJ box is 14:1, fixed ratio. 3-1/2 turns lock-to-lock.

But we're talking about a 1988 Jeep, not a 2014 Chevy. The Chevy might have a different type of pump. I cited the factory service manual spec for oil pressure. If you don't believe me, look it up for yourself.

I agree. The '01 steering box had been trashed by a previous owner and couldn't be adjusted, so I had to replace it anyway. If I had it to do over, I'd go to AGR Steering and buy a 10:1 box. (Which would NOT be good for large tires and rock crawling.)

Your pressure is basically fine, for a 28-year old engine. Factory spec is 13 psi minimum at idle, 37 to 75 psi above 1600 RPM (at operating temperature). So your warm idle is a touch below spec, but not unreasonable. It's the pressure while driiving that's of more concern. The faster the engine turns, the more oil pressure it generates. For NEW engines, around 50 to 55 psi at 60 to 65 MPH seems to be about the norm. 40 psi on the highway is lower than what we expect from a new engine, but you don't have a new engine.

The factory XJ and MJ box is 14:1 and 3-1/2 turns lock-to-lock. The 12.7:1 ZJ box is 3 turns lock-to-lock. I have a ZJ box in the 2001 XJ, and the factory box in my wife's 2000 XJ. The only time/place I notice any difference is when backing up and turning 90 degrees in the driveway. On the road I don't notice any difference whatsoever.

It's only a spacer. What's wrong with the factory unit?

The usual cause of this is a vacuum leak in the line beneath the battery tray, to the vacuum reservoir "blimp" that's mounted behind the bumper on the passenger side.

I agree completely. Driving an XJ or MJ without the sway bar is dangerous even at stock height. With a lift it's considerably more dangerous.

No. The Renix XJs and MJs have the throttle cable running to a bellcrank mounted on the driver's side frame stub ear. From the bellcrank, IIRC, there's a rigid rod that extends up to actuate the throttle body butterfly.

It also won't have any effect on bump steer.

I have always used sealant on freeze plugs. Nothing high-tech -- good, old-fashioned Permatex Aviation-Grade Form-a-Gasket.

Time to clean up the yard. There are too many hulks out there, and I expect the zoning enforcement officer to pay a visit any day. I'm not interested in getting into parting out the XJs on a formal basis. The reason they are here long since expired, so it's time to clean house. I've got a local yard that will pay me $75 each if they're complete, or they'll take them for free if I remove any significant parts. I'm sure they don't care about small parts. So ... who needs something that I might have? The two that are going are an '86 Pioneer 4-cylinder 5-speed (4WD) and an '89 Pioneer 4.0L automatic (4WD). Send me a PM if you need something that might still be on them.

Yep. And you can run a rough test of it by having someone watch the timing mark with the engine running, and have another person tap the block next to the sensor with a hammer. If the timing jumps, the sensor is working.

That is not what he said. Rather, the renix engine has a knock sensor that permits the ecu to advance ignition timing to the point where the engine knocks, then backs the timiing off. Eagle put a high altitude Crankshaft position sensor on his truck. The high alltitude CPS has a wider range of ignition advance than the normal CPS (octane requirement drops with altitude because altitude has the same effect as lower compression). So because of the High Altitude CPS and the high octane fuel, his ecu advanced the timing further than normal which improved the highway MPG. Without the High Altitude CPS, premium fuel would have done nothing at all for the MPG. That IS what I said. Back in 1988 and 1989, I didn't know about the high altitude CPS, and I wouldn't have bothered replacing the original with one until it failed anyway. Just running high test fuel should result in an increase in mileage -- IF you have a light foot, so the engine isn't spending a lot of time under load so the knock sensor has to keep retarding the ignition. The high altitude knock sensor should make more of a difference, but the difference is there without it. It does this because with the higher octane that reduces knock (ping, pre-ignition) the knock sensor doesn't retard the ignition as much or as far.

It should increase your gas mileage -- more if you run a high-altitude CPS. But only for the Renix years -- the HOs don't have a knock sensor. The real question is whether it will increase the mileage enough to offset the higher price of the fuel.

On the flip side of anecdotes, if you have a Renix with the knock sensor, then there IS a benefit to running high test -- if you run it all the time and don't have a lead foot. When my '88 XJ was new, I ran high test all the time. My highway fuel mileage was phenomenal -- like 28 MPG on a road trip from Connecticut to Vermont, loaded down for a weekend with a lady friend, her daughter and a friend of the daughter, clothing for a winter weekend in Vermont, and "stuff" to keep the two kids occupied for a weekend. Why? Because the Renix advances the spark as far as it can, then backs it off when the knock sensor detects ping. High test reduces ping, so at cruise throttle I was running with more advance than would have been possible on regular grade fuel.

No.

In your opening post you said you didn't have a welder. Then you wrote: Make up your mind. Modifying a truck for off-road gets expensive VERY fast. You're currently on 32" tires. Then you started asking about 35" tires. You don't need 35" tires for the type of off-roading you described. In fact, you don't even need 32" tires for that -- you could do it on stock-size tires with no lift. When Paragon was operating in Pennsylvania I ran just about every trail they had in a shortbed MJ on 31" tires with a basic Trailmaster 4" lift, and I could have run most of them just as easily with no lift. (I know, because I also ran most of them in a Cherokee on 30" tires with no lift.) The direct answer to your original question is that ONLY a Dana 44 from an MJ will bolt into an MJ. An XJ Dana 44 is the same width, but the spring perches are in the wrong location and have to be cut off and relocated, or you buy new perches and weld those on. Next choice (IMHO) is the Chrysler 8.25 axle from an XJ or maybe a Liberty. You want one from an '97 or newer, to get the larger, 29-spline shafts. The axle width is correct but, like the XJ D44, you have to relocate the spring perches. After that (IMHO) comes the Ford 8.8 axle. It's a tough axle, they're cheap, many have a limited slip already in them, and the newer ones have disk brakes. They are also too narrow. You WILL need to budget for buying spacers, or aftermarket wheels with a lot less backspacing than factory. The problem with using the wheels to fix the axle width is that if you run the same wheels in front -- they stick out too far. I think you need to sit back, take a deep breath, and reexamine your budget and your priorities. Then come back and tell us what you can realistically afford, and we'll try to help.

What size are they? Can't tell from the image. Does the text run the full width of a rear window, or just occupy a corner?

Both the Renix and HO 4.0L engines in the XJ and the MJ use a 2-1/2" down pipe. The catalytic converters are 2-1/2" all the way through, and the converter tailpipe necks down from 2-1/2" to 2-1/4" between the cat body and the muffler inlet.