Eagle

Yes, but witha PCV the valve itself gets plugged up. PCV valves are a routine replacement service item, but a lot of owners never touched them.

Where are they rubbing, and what wheels are you using? 31x10.50-15s will fit with no trimming -- if you use stock Jeep factory wheels. The factory wheels have 5-1/4" backspacing. No aftermarket wheel has that much backspacing, so any aftermarket wheel puts the tires farther out, and that can cause problems. On stock rims, the only rubbing will be at full steering lock when the inside shoulder of the tire on the insode of the turn (left tire on a left turn) rubs the lower control arm. This can be addressed by shimming the steering stop, teaching yourself not to turn the steering wheel all the way to full lock, or switching to WJ Grand Cherokee lower control arms, which have a built-in bend to accommodate that issue. I was reluctant to try shimming the steering stops because I was afraid they'd break, so I just learned to not turn the wheel to full lock.

No, the 4.0L has a CCV tube, the 2.5L has a PVC valve sitting on top of the valve cover. Check to see if the PCV valve is open or clogged.

Never assume. Guesses are good for deciding what to test first, but don't spend money on repairs until you know what you're repairing. If you suspect blow-by, the first test should be a compression test. Remember that all engines have some blow-by, and the Reniix 4.0L engines are known for having the CCV tube get clogged. When that happens, even normal blowby over-pressurizes the crankcase, and that's when you get oil dripping out of the smog tube into the air filter. You may only need to replace the CCV tubing and clean out the valve cover, but the first step is a compression test.

If he has a light, he doesn't have a gauge. But if the light isn't coming on, what reason is there to think that it's getting "super hot"?

I am well aware of what can happen when a u-joint fails. However, the OP wrote that Since everything at the differential end is bolted together, there is nothing that can "slip out." Before we can offer any advice, we need to properly understand what happened ... and I cannot figure out what happened from the description provided.

We need photos, and I'd also like to know if the axle in the truck is the original axle. Whatever happened, it doesn't sound good, but your post left me feeling more than a little confused. I don't know what you mean by "spindle," but there's no part of the drive shaft that can pull out of the rear differential. The yoke is attached to the pinion gear by a nut, and the driveshaft is attached to the pinion yoke by straps with nuts on them. The axle sits on the leaf springs with mounting pads that are flat on the bottom and welded to the axle tubes. Even if the u-bolts were loose, I don't see how that could be loose enough to allow the axle to rotate far enough for something to pull apart without the big axle u-bolts falling off.

Factory spec for caster is +7 to +8 degrees, but 6 may be the best you can do with a lift because of U-joint angles. I'd say it's marginal. Factory spec for toe is zero, plus-or-minus 1/32 for each side, so it shouldn't be more than 1/16 toe-in. But I don't think 1/8" of toe-in would be enough to create any problems other than a bit of premature wear on the outer shoulders of the tires.

10-4. My buddy at the VW shop uses a Hunter Road Force machine.

This post has been split off from the discussion of Knucklehead97's death wobble because it has nothing to do with that topic of discussion.

No. As proven by my driving my '88 XJ all winter with a VERY loose track bar and zero death wobble.

Topic split to avoid confusion.

But ... If he's been driving on these tires for several months, they're not brand new. If the tires are brand new, then my comments about tire balance apply. Also, was the alignment done at the same time the tires were installed? Basically, Knucklehead, you have been driving with no problems for several months. Now you have death wobble. What changed recently? That's where to start looking. When was the alignment done? Several months ago, or just a short time before the death wobble made its appearance? Death wobble is a complex issue. After all the years Jeep was making solid axle vehicles, you'd think they had it figured out. But ... when the 1999 WJ Grand Cherokee came out, it had a problem with death wobble. The problem only affected the European models, with export suspension. The difference between the Euro vehicles and the American vehicles was the durometer (hardness) of the rubber bushings in the front suspension. (I assume this referred to the upper and lower control arms.) One of the usual "causes" cited for death wobble is loose joints, including the track bar. But with my original '88 XJ, the original track bar eventually got so sloppy that I had nearly a quarter turn of "slop" at the steering wheel. It was winter here in New England, we had a lot of snow that year, and I didn't have an indoor garage to work in. So I drove it like that for a period of several months. I experienced no death wobble. So I don't accept that loose joints "cause" death wobble. They probably make it more exciting if it happens, but they don't cause it. Death wobble occurs when an imbalance in one front wheel is transmitted to the other front wheel, and the other front wheel then begins to wobble/shimmy at the same frequency. With both wheels wobbling at the same frequency, they enter into a harmonic where each wobble of one wheel amplifies the wobble in the opposing wheel. That's what death wobble is, and that's what differentiates it from simple wheel shimmy that's not reflected at the opposing wheel. Sloppy TREs don't transmit wobble from one wheel to the other. In fact, they would tend to allow a certain amount of wobble to occur before reaching an amplitude that would transmit back through the steering linkage. An automotive tire/wheel assembly is a gyroscope. If it's properly balanced, it should be very difficult to make it wobble, and the faster it spins the more difficult it becomes to make it wobble. For that reason alone I always look first to wheel balance as being the underlying cause of any death wobble incident. Other things, sich as worn steering components, may contribute by allowing it to escalate, but they aren't the cause. What were the alignment specs? Caster angle is crucial because caster helps resist/dampen wheel wobble -- did you set caster angle? If so, what did you set it to? If not -- what is it?

You drove it for 30 miles with death wobble? I respectfully submit that I do not think you had death wobble. I have had death wobble. Once would be enough for anyone, and there is NO WAY I could have driven for 30 miles with what I had. There was no way I could have driven ONE mile. I was, literally, scared to death. It was all I could do to keep it on the road long enough to slow down to under 5 MPH to end the death wobble. After that, until I got it home and swapped tires, I kept it under 40 or 45 MPH.

If you mean as a direct replacement for the MJ bench seat, the answer is no, it won't fit.

Yes, the alignment specs may be different with a lift. You didn't list all the components you used to get your 4.5" lift. In the XJ/MJ front suspension, caster angle is adjusted by adding or removing shims at the rear end of the lower control arms, to push the LCA locations forward or back, thereby rotating the axle tubes and changing the tilt angle on the Cs and steering knuckles. That's what caster angle is -- the tilt in the forward-to-aft axis of rotation of the ball joints. Positive caster is when the lower end of this axis is forward of the upper end. Positive caster is what helps generate good tracking at highway speeds, but it is also important in preventling death wobble. So HOW you achieved your lift and what alignment specs were used is important. The effect of just adding a lift, without replacing the LCAs with longer or adjustable LCAs or adding a lot of shims, is to reduce the caster angle. If you reduce the caster angle significantly, you greatly increase the probability of experiencing death wobble. This is why so many aftermarket companies sell adjustable LCAs. Even then, you get into a delicate balance. With taller lifts, you're also messing with the U-joint angles in the front drive shaft. Trying to put the caster angle back to within factory specs with a significant lift results in excessive U-joint angles. Consequently, you have to search for the sweet spot between a caster angle that won't kill your U-joints and a caster angle that will be enough to prevent death wobble. There has been a lot written on this topic, both on this forum and on NAXJA.

Why "must" it be a design flaw? I currently own three XJs and three MJs that I have personally driven significant distances, plus a 2001 XJ that I sold to a friend awhile back. Among all of them, I probably have close to half a million miles racked up. I bought my first XJ in early 1988, so that's more than 30 years ago. The original '88 XJ alone has 287,000+ miles on it. Out of all those miles, the only one that ever experienced death wobble was the red '88 MJ. The death wobble occurred when it had the 4" lift installed (later removed) and when I had it on 31-inch tires. The cause was tire balance, and the cure was to put a different set of tires on it. Solid front axle vehicles are inherently more prone to death wobble than independent suspension designs, but that doesn't mean there is a design flaw in the Jeep solid axle design. It just means we should not make a bunch of changes without being aware that changes may have consequences.

Then the tires are probably the cause. I've been through this twice on my XJs. New tires, mounted and balanced at the tire shop, get on the highway at about 55 MPH and the front end starts to shimmy. Never gets to full death wobble, and if I speed up to about 62 MPH or faster it smooths out again. Take them back to the shop, they balance them again ... same issue. I have a friend (former XJ and MJ owner, currently has a ZJ) who works as a shop foreman at a VW dealership. Both times, he took the tires and balanced them for me and they've been perfect ever since. Too many techs these days don't know how to use the tire machines. I had one shop tell my my Jeep factory alloy rims were bent so they couldn't be balanced. My friend put them on his shop's Hunter machine and he said the wheels were perfect. The "technicians" at the other shop didn't even know how to attach a wheel the the machine, why should I expect them to know how to balance a tire? Here's a clue: This has been true ever since I can remember, going back to my mother's 1958 Rambler station wagon: for some reason, tire balance issues ALWAYS manifest at 55 MPH. If you can drive through it and it smooths out above 62 (or so), it's not a death wobble or suspension issue, it's a tire balance issue.

To expand on Hornbrod's response -- "it depends." That grille won't directly bolt onto your header panel (that's the fiberglass section in front of the fenders, to which the grille attaches). However, it's really not a big deal to just swap the entire header. That vehicle has the older, 10-slot grille, which is less common than the 8-slot grille, which then became a liability for Jeep when they found themselves trying to claim copyright (or trademark) infringement on other makers who had the temerity to put seven vertical slots in their grilles. Nowadays, every Jeep vehicle has a seven slot grille, even if it looks stupid. That bumper is in nice shape, too. And it has the steel license plate holder, which is much more durable than the plastic ones used in later years. (I don't know what year they switched, but my 2000 XJs have plastic, and it sucks.) So, if you're willing to do a bit more work, putting that nose on your truck is a bolt-on swap.

Liar, liar, pants on fire! [See my signature!]

Then you should be able to sell them for what you paid for them, or more. The problem is, the helluva deal on the tires is going to cost you a helluva lot of money. To run those things, you need new lower control arms just for turning clearance. You need at least a 4-inch lift, and a 6-inch lift would be better. When you get into that much lift, you need: An adjustable track bar Adjustable lower control arms Adjustable upper control arms A rear lift, either a spring-over conversion, new springs, or an add-a-leaf plus shackles Longer shock absorbers on all four corners New, longer flexible brake hoses A major wheel alignment I'm sure there's something I've forgotten, but you get the idea. Whereas, you can run 31x10.50s on factory Jeep wheels with NO lift at all, or maybe a 2-inch budget boost if you feel you just have to do something to it. But a stock MJ is a very capable off-road truck even at stock height.

This isn't a private conversation between you and Don, this is an open discussion. All you said was that your '89 has "them." You're apparently referring to the side body moldings, but this thread started out about the underbody fairings/rails.

I have to disagree. Someone earlier in this thread already noted that there were fewer than 1,000 '92 MJs built. It certainly IS super rare, and IMHO for that reason alone it should be preserved in original condition rather than hacked to put on bigger tires that probably aren't necessary for the limited wheeling Mancheflo will be doing. Value is a different matter, but if it's preserved in original configuration and taken care of, the value will only go up. As soon as the sheet metal gets cut, the value plummets. It is his truck, and it's his decision. That said, I still think it's a very bad idea to start cutting up a pristine example of a very rare Comanche. Especially since it's a longbed, which isn't a good candidate for wheeling anyway. The shortbed MJ is much more nimble on the trail. The shortbed has a better breakover angle and a better departure angle.

Look underneath. The transfer case and drive shaft are below the "frame" (unibody) rails. A flat belly pan isn't possible.