Eagle

Burping is for the Renix-era closed system, not the later open system. We still don't know what year this truck is.

I believe you can buy "power chips" to fit the OBD-1 HO engines. I know they are available for the 4.0L engine in the ZJ grand Cherokees. However, every review I've seen (disclaimer: I haven't looked at this for several years) reported that it was necessary to run premium gas with the power chip installed. So you get more power, but you pay for it. With gas hovering around $4/gallon for regular, personally I would not be in a rush to install a mod that requires me to spend an extra 30 or 40 cents per gallon.

I would try to grind a flat surface. The u-bolts are much stronger than the straps.

He didn't ask about updating an 89 into a 99, he asked about making the 89 4WD. I agree with benjy_26 that an earlier year would be a better donor for the conversion, but if he already has the 99 he can do it.

This thread is about a Dana 35 rear axle. Your question is about a Dana 30 front axle. They are completely different. I believe you have an older front axle with the passenger side disconnect. If that's correct, there is no seal at the diff housing on the passenger side -- the seal is located at the point where the disconnect housing is located, so diff lube can lubricate the sliding disconnect mechanism. Since you already have another thread open to discuss your problem, I'm closing this one.

(1) There is no rear Dana 30 axle -- at least, not in a Jeep, and not in any other vehicle I ever heard of. (2) Jeep never offered a locker in an XJ or an MJ. They offered as an option a limited slip for the rear axle, but not for the front. I suspect you must have an older MJ with the front central axle disconnect. It's not a locker, all it does is allow the two front wheels to rotate independently, which leaves the differential and front drive shaft doing nothing when in 2WD mode. I'm pretty certain the seal you need is one of these: http://www.autozone.com/autozone/parts/1989-Jeep-Comanche-4WD/Axle-Shaft-Seal-Front/_/N-iuaiqZ6o3am?filterByKeyWord=front+axle+seal&fromString=search Note that some say they are for the "disconnect" axle, and some are not. I believe you have a disconnect axle, so look at those listings and tell us if one of them looks like your old seal.

We NEED to know what year this truck is, because the auxiliary fan operation is different between the Renix-era models and the later HO models.

You are correct in what it does. It was for the Renix models only. For the HOs, the ECU handles that function. I don't think it adds any power or torque, unless you run mid-grade or hightest gas. The Renix engines have a knock sensor to retard the spark when they sense detonation. And that usually happens under load. What the high altitude CPS really does is allow more advance under light load, which boosts the fuel economy.

They don't fit. Once again, the XJ rear wheel opening is smaller in both length and height than the MJ. 2-door and 4-door XJs have the same wheel opening and take the same flares.

Are those still available? I thought I bought the last one in captivity about four years ago.

More power and torque in a 2.5L? One word: "Cam"

Thoughts: (1) It almost certainly doesn't have an AX-15 transmission, because Jeep didn't start using that until mid-1989, and it only fits the 4.0L. Your son may have an AX-5. (2) Jeep wasn't using the 231 transfer case in 1986, either. You probably have an NP 207. (3) Do NOT try to bore out a 2.8L to 3.4L. You may or may not be able to bore it that much, but the later 3.4L engines had MANY improvements over the 2.8L, and just boring out a 2.8L won't get you any of them.

That's always a good place to start. It also helps the parking brake to work (a little).

Sorry -- not possible. First, unless you get VERY lucky and find a Comanche in a junkyard with a heavy-duty axle, more than likely you'll be getting an axle from a Cherokee. The Comanche is spring under axle (SUA) and the Cherokee is spring over axle (SOA). Also, the distance apart for the spring perches is slightly different for the Cherokee. So there's basically no way to avoid welding spring perches (unless you luck into a Comanche Dana 44). Second, both the Dana 44 and the Chrysler 8-1/4 are about 1-inch longer than the Dana 35, so to use either (at stock height) you will probably have to get the driveshaft shortened.

"Tiny" doesn't tell us anything. What size are they, and what load range are they?

It very well could be the proportioning valve. The XJ proportioning valve is built into the distribution block under the master cylinder. The circuit feeding the rear brakes goes through the front end of the block. Inside, there's a plunger with an O-ring and a very strong spring. Under light braking, there isn't enough pressure to move the spring, so the plunger keeps the rear blocked and the front brakes do all the work. In theory, under heavy braking, there's enough pressure to overcome the spring, moving the plunger and opening the circuit to the rear brakes. My '88 XJ hasn't had any rear brakes for about four years -- I've tested it on snow and ice. NO rear brakes. What I think happens is that, because the rear brakes normally don't get used, the plunger in the proportioning valve gets gummed up, and then when you need it it can't move. I keep meaning to remove the plug from the nose of the proportioning valve and clean it out, but I don't drive the '88 much any more so it hasn't been a priority.

As I and others have pointed out, a Comanche with Metric Ton springs has a payload of 2200 pounds with no need for special wheels or tires, so that takes care of your 1500 wish list.. Use standard Jeep wheels, go to Wal-Mart, and get a set of the original Wrangler Radials for $88 per tire. The ony size available these days is 235R75-15, which is one size larger than the largest tire offered from the factory but which is (IMH) a perfect tire size for a street XJ or MJ. No upgrades to the frame are necessary. As others have pointed out, to tow a heavy trailer you do need heavy-duty cooling and you should have a heavy-duty axle. In the days of the XJ and MJ, the oprional heavy-duty axle was the AMC Model 20 in 1986, and the Dana 44 after that. The '97 and newer Chrysler 8-1/4 is just about equal to the Dana 44 in strength, so that's also a possibility. First, you need to know what axle you have. Post a photo of the rear differential.

It's an '88, which means it is essentially an AMC even if it was built after Chrysler bought AMC. AMC was notorious for over-boosting their power steering. It's characteristic of the breed. I've always been an MC owner (since before they were AMC) so it doesn't surprise me, but it always bothered me. In my Javelins and AMXs I ran quick ratio manual boxes because I couldn't stand the power steering. My early XJs and MJs all have too-light steering and basically no road feel, but I've never felt like spending the money to have a box rebuilt with a stiffer spool valve.

??? With metric ton springs the payload is 2200 pounds. Of course, the Dana 35 axle may not stand up to that too long. You need either an XJ or MJ Dana 44, an MJ AMC Model 20, or a 97 or newer Chrysler 8-1/4 out of an XJ. The Chrysler axle would be my last choice because of the puny 9" brakes, but it's also probably the easiest to find. I don't think you should even consider bumping the payload over 2200 pounds. The frame won't be happy.

One more time: That tank on your firewall is not -- repeat NOT -- an overflow tank. It is a part of the pressurized cooling system. The '87 - '90 4.0L MJs do not have any cooling system overflow. They have a closed system. The cap of that tank is the pressure cap. The tank is an expansion tank, and must be filled only to the halfway mark when cold.

I did the timing chain on my '88 XJ 4.0L around 200,000 because I remembered that the older AMC V8s used nylon teeth on the large sprocket and I was afraid mine was probably about worn out. In fact, it was as good as new -- virtually no slack at all. I put the new timing set in as long as I had the engine open, but I still have the old parts and I wouldn't hesitate to install them in a beater engine. I'm familiar with double roller timing chains, but I've never heard the term "double braced."

??? What's a triple braced link? The parts in your photos look like the OEM parts, and they look like every 4.0L timing chain set I've ever seen.

Yep. No need to have two threads on the same topic.

Why? Unless you are going to run huge tires and you frequently get really crazy with the gas peddle, the dana 30 is all you'll need. How about a photo of the rear axle? If the seller lied about the front, he may have lied about the rear as well.

^^^ This.