Eagle

What 2.5L engine are you referring to here, the Iron Duke? The Jeep 2.5L has the same bell housing bolt pattern as the 2.8L/3.4L V6.

It's not an ignorant statement. It's a statement based on multiple observations over the course of 24 years of owning and driving Xjs. I've seen many small-blocks in XJs, and they have ALL had cooling problems. If it weren't a persistent problem, it wouldn't come up so often on so many Jeep forums. Are there some people who have made it work? Sure -- but it won't happen by accident, and it costs money. If the goal is just to gain a bit of power and reliability over a 2.8L, doing the small-block V8 conversion is a waste of money and effort.

The article is incorrect. Every XJ/MJ lower ball joint I've seen has a hole for a grease fitting, and they come with both a Zerk and a plug. The routine is to install the ball joints, insert the Zerk fitting and grease the ball joint, then remove the Zerk and install the plug. The plug sits low enough that the u-joints clear it when rotating.

Did you test the starter relay? If you know that's good, then you need to check the ignition switch.

Pretty much everyone who has swapped in a 3.4L for the 2.8L has been very satisfied with the results. It's a better, smoother-ruuning engine that also produces more horsepower. And what it WON'T do is create all the cooling problems that plague the small-block Chevy V8 conversions.

I don't believe there are any sensors under the dashboard (but I don't have an HO vintage MJ, so I'm not certain). What would there be to sense? The sensors are all under the hood, they feed into the main harness under the hood, and there's a single connector that plugs into the back of the instrument cluster (and a smaller plug on the left of the cluster for the various secondary status lights).

Let's use better terminology. "On" = "ignition." You have ignition when the key is on the On or Run position, otherwise the engine wouldn't run. When you turn the key beyond On to the Start position, all accessories should be bypassed and the starter should engage. So if by "on" you mean the run position, you should have instrument warning lights, but the ignition switch should not be turning on any interior lights. If by "ignition" you mean "Start," then you need to figure out why the starter isn't engaging. Have you checked the starter relay? Can you jumper to the solenoid and engage the starter? If not, the solenoid may be bad. If the solenoid clicks but the starter doesn't do anything, the starter is bad.

Going to tires that are several sizes larger than stock is like going the wrong way with an axle gear change, or shifting into overdrive. And the 2.5L doesn't have the Moxie to run an overdrive with that axle ratio. There's a reason the factory used 4.10 gears behind the 2.5L with the 5-speed. Your factory tire size should have been 205/75R15. My chart doesn't even go that small, so I have to look at 215/75s. For that tire size, 60 MPH equates to 2669 RPM, which is below the 3250 RPM torque peak for your year. 70 MPH is 3115 RPM, which is effectively right at the torque peak. Try to go faster, and as the drag increases your torque decreases. With 235s, the 60 MPH engine speed drops to 2556 RPM, which is a loss of about 5 percent. That's about the equivalent of changing your axle ratio to 3.31. It puts you below the torque peak, and WAY down on the horsepower curve.

Calibrate = good. Calibrate to another vehicle = bad. There's very little chance that the speedometer on another vehicle is really going to be accurate. If there's a police department near you that deploys those radar speed sign trailers, run your MJ through that and see what the radar reports compared to your speedo. Or borrow a GPS and calibrate to that. I haven't checked any of my MJs, but I have checked four (4) XJs, and the speedometers on all four read from 2 to 4 MPH faster than actual speed, on stock tires with no changes to gearing. And that's been checked both by radar trailer and (for two of them) GPS.

Exactly what is it doing or not doing? Does it turn over but not fire, or not even turn over?

Worse. Actually, maybe the same. 30x9.50s are almost the same diameter as 235/75-15s, but wider, so they offer more drag. But with a 4-cyl 4-speed, your 235s are several sizes larger than stock already, so unless you have changed the speedometer gear, your speedometer is reading slower than your actual speed by somewhere around 5% to 7%. Since it's a 2.5L 4-speed, it must be a base model and you probably don't have a tachometer. FWIW, 65 MPH on the speedo (based on stock tires) is almost 3,000 RPM. The engine will turn faster than that, but remember you're driving a brick on wheels, and both aerodynamic and frictional drag increase exponentially with speed. At an indicated 65, you are probably actually going closer to 70, and that's going to be ruining your gas mileage because that comparatively small engine is having to work a lot harder to push that brick down the highway. You would probably gain more speed (if that's what you want) by going to 215/75-15 tires. Let me offer a real-world experience. When I was in the Army during the Vietnam unpleasantness, for awhile I was stationed in Maryland. At the time I was driving a Rambler American. The engine was the 199 cubic inch version of what ultimately became to MJ 4.0L, and I had a 3-speed manual tranny. Like your 4-speed, top gear was 1:1 -- no overdrive. After a bunch of tinkering, running high-test gas so I could bump the timing, running an open air cleaner and a glasspack muffler, I was able to finally get my top speed up to an indicated 104 MPH (tested late at night on I-95 not far from my post). That was on the stock tires. Then winter arrived. My brother was driving a full-size Rambler Classic V-8, which came with much bigger tires. He had switched over to radials, so he gave me his bias-ply snow tires from the year before. They looked silly on the back of my little American but, more important, my top speed immediately dropped from 104 to 84 MPH (indicated). Even after correcting for the larger tire size, my real top speed dropped by at least 10 MPH. The reason was that the power curve of the engine crossed the line for power required to push the brick -- there just wasn't anything left at that point to make the car go any faster.

What year MJ? I think the clutch interlock was introduced in 1994, so it should not have been found on any MJ.

Yes, it is as easy as telling a welder to "make this axle look exactly like that one." The stock spring perches are only welded along the outside, so it should be easy to grind the welds and pop them off intact and reusable. The XJ axle will have shock mounts welded to the tubes -- you don't need them and won't use them, so you can either grind them off or just ignore them. I think it's probably going to be a LOT cheaper to move the spring perches than to pay someone to swap the gears to the old axle. If you do the swap, at the very best you'll have used gears that are only "close" to the way they were set up from the factory. Plus -- your old axle is a mess. God only knows if one or both tubes might be slightly bent. If so, putting new gears into a bent axle is just asking for another failure. IMHO you're much better off with an axle that was set up from the factory.

??? What's the worry? The motor mounts go in the same place.

The fabric for headliners is a special product with a backing to accept the spray adhesive. It's cleverly called "headliner material" and in any Joanne's Fabric store should have its own section or aisle in the store. Ask -- it's usually toward the back and not easy to find.

Why would you say that you know everything will not fit right in? It should -- you'll have the engine, dashboard and wiring harness all from the same donor vehicle, so why would everything NOT fit right in? The only real issue is going to be mating up the front harness from the XJ to the taillight wiring in the MJ. How far did he get swapping in the dahboard? I'm not 100 percent certain about the HO vintage, but with the ECU mounted under the hood, I would think it should run even if you don't have a dashboard.

Many people have done it, but it is work. You have to change all the underhood wiring harness. If you're going from MJ to MJ, you have one advantage -- when people do this swap using an XJ as the donor vehicle, there's a some customizing required to make the brake lights function correctly.

Slow down, Mate. You are apparently thinking that you can just bolt that XJ axle under your MJ and go. Unfortunately, it isn't that easy. The springs on the XJ are spaced differently -- laterally -- than on the MJ. To use an XJ axle in an MJ, you MUST cut off and relocate the spring perches, whether you're going spring-over or staying spring-under.

Fast idle on start-up is often caused by a dirty IAC (Idle Air Controller). For the hesitation, I'd guess that you made too many mods to the intake and exhaust, and it's now flowjng enough that the 19-lb injectors aren't supplying enough fuel. The hesitation sounds exactly like what I felt in Bob Salemi's Renix stroker when he first put it on the road. He cured it with a set of HO injectors, IIRC.

I called my dealer today to see about ordering some caster shims and a pair of lower control arm clevises. The clevis is the bracket that fits inside the LCA frame pocket and has the two studs that allow you to tighten it in place after adding or removing caster shims. Bad news: the shims are still available, but the clevises are NOT available. Anywhere. There were none in the system, not even showing up in other dealers' inventory. I'm going to need to check (and probably adjust) the caster on the 2000 XJ I bought for my daughter. Considering that this XJ has spent 11 years all in serious rust-belt states, I have to assume that I'm going to snap at least one of those studs trying to loosen the nuts to adjust the shim packs. If any of you in NON-rust-belt states are going to be hitting a pick-n-pull junkyard, I'd appreciate it if you would try to grab me at least two of those clevis assemblies. And for the rest of you -- if you can grab 'em, please do so. Sooner or later, a fellow Comanche Club member will be in need, and (as the saying goes) "They ain't makin' 'em any more."

There are numerous higher-power Delco alternatives for the Renix MJs. What you have to be careful of is that the higher-output alternators have a bigger winding (no $#!&, Sherlock, that's how they get higher output), and if the winding gets much bigger than stock the alternator won't fit. Look at Mean Green.

You could run mis-matched gears and leave the front driveshaft in place ... as long as you never put the lever in 4WD. Yes, if you remove the driveshaft there is nothing to connect the front and rear axles, so mis-matched gears won't matter.

With a 2.5-liter 4-speed, your rear axle is almost certainly a 3.54. Fortunately for you, that's the most common axle ratio in 4.0-liter XJs, because that's what the factory used with the automatics. Just bolt it in. To echo a previous post, you do not need a lift to run 31" tires, and you do not need a lit for moderate trail riding. Keep it at stock height, drive it for a year, THEN decide if you really need a lift. Once you lift, you've just dug a deep hole that you keep pouring $$$$ into.

I think we found your problem ...

Pete, I absolutely have to disagree with you on this. The two Comanches I've had on the road, as well as several Cherokees, have all been 4WD with limited slip diffs -- mostly factory Trac-Lok, but the red '88 MJ has a TrueTrac. I'm in snow country, and with the limited slip rear axle I almost never have to use 4WD. I won't own one that doesn't have limited slip -- got a new Trac-Lok in the box now, waiting to put into the used XJ I picked up for our daughter. Snow tires, or decent all season tires, are a must, of course, but the limited slip in a 2WD will often make the difference between driving home and walking home. (Don't ask me how I know this ... I don't choose to discuss it.)