Eagle

The first step is to hook up a good, verified accurate, mechanical oil pressure gauge and check the oil pressure at 1500 and 2000 RPM. This can be done in the shop -- the engine doesn't care if your actually driving or not -- oil pressure is a function of RPM. Period. Assuming that your 20 psi is an accurate reading, then you need either new bearings, or a new oil pump. Rings don't affect oil pressure so it doesn't matter if the engine smokes or not. Seals don't materially affect oil pressure, either, because the pressurized part of the system isn't pushing oil at the seals. What matters is the clearance at the rod bearings and the main bearings. This can be checked with the engine in the vehicle, using plastigage. It is necessary to drop the pan. It is also necessary to drop the pan to replace the bearings or the oil pump. I think you need bearings. The fact you can get higher pressure if you rev up the engine tells us that the oil pump is capable of producing pressure. The most likely problem is excessive clearance at the bearings.

J trucks were all 6-lug or 8-lug, were they not? Even my '79 full-size Cherokee was 6-lug.

Removing the valve cover and cleaning it up would be a good idea. There is a baffle inside there that can get clogged. Can't hurt. Before you change the fuel pump, have you replaced the fuel filter? It's mounted on the driver's side frame rail, sort of near the back of the cab. Most owners don't know it should be changed regularly.

207? You already have high lock and low lock ranges.

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jesus, that was fast!! OK so the switch on the clutch is for cruse? There's one for cruise (if you have cruise), and one for brake lights. The clutch starter interlock wasn't used when the MJ was in production. It showed up during the latter years of the XJ but I don't recall which year. All of which reminds me, I need to bypass that in my 2000 XJ. I have had to drive the '88 XJ home from over 100 miles away without any clutch when the slave cylinder went south. I don't like doing it, but it's better to be able to when needed than to be sidelined by a stupid interlock.

WHAAAAAAAAAT? Where do you guys get all this misinformation? You must hang around with a bunch of Jeep haters or something. For the record, I'm an AMC guy since before Hudson merged with Nash to become AMC. I have owned and driven every cubic inch variation of this engine, from the lowly 199 cubic inch version in a 1966 Rambler American right up to two 2000 Cherokees sitting in the garage. There has NEVER been a problem with these engines and low oil pressure. Every single one I've seen that was anywhere near new ran 55 to 60 psi at 55 MPH. My '88 XJ is currently at a shade over 260,000 miles and it still runs 45 to 50 psi at 55 MPH. Sheesh!

'88 MJ 4.0L, 5-speed running 3.73 gears and 31x10.50 tires I typically got 19 MPG in mixed driving and 21 or 22 highway. The '88 XJ 4.0L 5-speed in completely stock trim (with 260,000+ miles on it) still delivers 20 to 21 MPG in mixed driving and 22 or so highway. You should be right around 20 MPG or maybe a bit better if you drive semi-sanely.

The Exploder 8.8 is marginally tougher than the Mopar 8-1/4, BUT ... Consider that the Ford axle is too narrow and that you'll have to run spacers just to keep even stock tires from rubbing on the sheetmetal. Either that or run ridiculous backspacing that'll leave the front wheels sticking way outside of the flares. Plus the Ford axle has an offset differential -- not a major issue in an MJ, but a consideration. The Mopar axle (97 and newer XJ will have the 29-spline shafts) is the correct width for an MJ. Weld on the perches and you're ready to rock and roll. I know a lot of people seem to think the 8.8 is a wonderful idea, but IMHO it's ridiculous. Unless you need the deeper gearing options available (but not standard) in the 8.8, the Chrysler axle is so much less work that to me it's a no-brainer.

Good luck ifyou think any of the aftermarket places have a bracket for a stock, OEM rear bumper. (We are talking REAR bumper, right?) If they list anything, it'll be the universal bracket for a Fey step bumper. I went looking for a factory rear bumper bracket maybe two or three years ago. They were no longer in the factory warehouse. My dealer tracked one down at a small dealership somewhere in New hampshire and I bought it over the phone, sight unseen. The parts guy there thought it was used and sold it to me for a used part price, but if it as used I can't see where or how. Unfortunately, it may have been the last one in captivity. And they are side-specific -- they are mirror image, not universal.

do you know if these are clipped and how much effort is to keep these in the SUA vice SOA just a personal pref. for me :hmm: If by "clipped" you mean are they c-clip, the answer is yes. And the spring perches are located the same as for an XJ D35, which means they are spring over but NOT the same spacing as for an MJ. So to use it in an MJ, regardless of SUA or SOA you either have to relocate the perches or simply weld on new ones (if you're going SUA). Like all XJ axles, they also have the lower shock mounts welded to the tubes. You can leave those in place and simply not use them, or if you're concerned about ground clearance you can cut them off. I would cut them off.

What ratio, and how do you use the truck? So many people have upgraded from the D35 that someone here might just give you a set of used gears, if used gears would be all you need. If it's a street truck, though, the D35 is adequate and putting in an XJ axle would be an acceptable solution. However -- for the same amount of work, you could drop in an XJ Chrysler 8-1/4 axle. Any of them are better than the D35, and the 97 and newer have larger 29-spline axle shafts that approach the D44 in strength. If the junkyard will sell you one of those for not too much more than a D35, that's probably the way to go.

It depends on which axle (front or rear), and what aspect of your axle is bad. Keeping in mind that any XJ axle you get is going to be used, it might make better sense to repair what's wrong with yours than to swap in a different with its own potential problems. Plus there's the issue of matching gear ratios. If the XJ axle isn't from within the same year range as your MJ, the knuckles, hubs and rotors will be different and that means you won't be able to use your MJ calipers, you would have to use calipers from the same year as the axle. Why don't you give us a bit more information on what the problem is with your axle?

Sure you have. All the Jeep relays are double throw. I don't remember the terminal numbers off-hand, but they are set up so if you wite them one way they are normally open, and another way they are normally closed. Yes, you could use that to operate both headlights off one relay.

You only need two relays, one for high beams and one for low beams. If the relay is in the vicinity of the battery and the lights and you use 12-gauge wire, you'll get plenty of juice to the lights. Running multiple relays won't change anything -- voltage drop is a function of wire gauge and length. Plan your wiring layout to minimize the length of the wire run and you'll get maximum power to the lights.

It may be one (or more) partially clogged injectors. When the engine is cold, it does not respond to sensor inputs. During warmup, it runs in "open loop" mode, which means it ignores the sensors and runs on a pre-mapped fuel curve that's built into the ECU. With the '88 XJ, I have owned it for so long that in the winter I can feel when it switches. It's about 2 miles down the road, on a level area where I run at neutral throttle. Right in that area on cold morings I usually feel a slight jump and after that the throttle response changes subtley. Once the sensors cut in and the O2 sensor starts reporting the mixture to the ECU, the ECU can compensate (to the extent the injectors have enough capacity -- which they would at idle) for clogging, but the pre-mapped fuel curve would have no way to compensate for this condition.

Is the Eaton supposed to be a limited slip when it's not locked? I thouhgt that one was either open or locked.

The grinder is not necessary. If the interior panel is already gone, you can reach inside the door and unlock the latching mechanism by hand. I've done it, but it was long enough ago that I can't accurately explain what I did. It was NOT done using the rods -- you have to reach the actual latching mechanism, and my recollection is that there's a "thingie" that one of the arms attaches to that you push either upward, or laterally.

It's a battery. Of course it can explode.

I think you mean "less" backspacing. You want to move the tires out away from the vehicle centerline, correct? Bolt circle is 5 bolts, 4-1/2" circle. The studs are 1/2x20

Vacuum leak. The flappers in the dashboard are controlled by vacuum. They default to the defrost position if vacuum is lost. The most likely problem spot is where the vacuum lines run under the battery tray to the reservoir, which is (if your truck is stock) located on the right front, behind the bumper. The reservoir is a plastic sphere or suasage, and it's also possible that the reservoir has been cracked, which would also result in loss of vacuum.

XJ/MJ/ZJ/TJ coil spacers come in two sizes: 3/4" and 1-3/4". For a daily driver, personally I would go with either XJ 4.0L springs and the 3/4" spacers, or if you stay with the springs in the truck now use the 1-3/4" spacers. Either way, you should end up just a little higher than stock. That's good for up through 31" tires, so why go higher if the truck lives on pavement? All unnecessary altitude does is kill the gas mileage. For the rear, what spring broke -- a main leaf, or one of the other leaves? XJ spring packs are too short for the MJ by about 5" but you could cut the eyes off an XJ main leaf and use it as an AAL in an MJ pack. That's what I plan to do with the 89 longbed I picked up. I'm hoping it'll result in the equivalent of a metric tonne load capacity without much extra lift.

Putting a lift on cannot change the camber. The camber is built into the axle and does not know how far the body sits above the axle. I know about the offset ball joints. Never heard of "cams" for XJ/MJ ball joints, and having changed a few I cannot understand how or where any "cam" could be installed. If your camber is really out of spec and you don't want to use the offset ball joints, then I would second the suggestion to buy a different front axle assembly.

The brake lights are activated by a mechanical switch in the brake peddle arm mechanism. Look under the dashboard and see if the switch is positioned so that depressing the peddle allows the plunger to come out of the switch body. You may just need to adjust the switch position, or you may need to replace the switch. You can test the wiring to the switch by unplugging them and using a jumper (or a paper clip) to close the circuit. If the brake lights don't work when the switch contacts are jumpered, then the problem is in the wiring harness rather than at the switch.

JC Whitney used to have patch panels and complete bed sides in their catalog a few years ago. Has anyone called them to ask if they are still available?