It had high NOX readings. I bought a new O2 sensor and a Flowmaster catalytic convertor, which did the trick and the Jeep passed emissions. The downside is that there is extreme pressure pushing oil out of the dipstick tube and I had to purchase another catalytic convertor last year.

I realize I must perform a leakdown test to see what exactly is going on inside the engine. Would it be more cost effective to rebuild it than swap it out? It’s only got 149,000 miles. I do plan on keeping the Jeep, upgrading the axles, and putting on a 2 1/2-inch Skyjacker lift kit.

My other plan is to upgrade to a Ford 5.0L truck engine and get an AX-15 transmission. What is the best bang for the buck option? It already has a Gale Banks header and an Airaid intake.

The Jeep is a blast to drive on- and off-road, and with the 4.10:1 ratio axle gears it moves out nicely!Sean Jennings Via email

Except in extremely rare cases, an engine rebuild or a remanufactured crate engine will always be more cost effective than an engine swap. Engine swaps have many costs and complexities that are often overlooked. These costs add up quickly and include things like the wiring, adapters, engine mounts, radiator, exhaust, driveshafts, fuel pump, and fabrication. These items can easily add up to a several thousands of dollars. Given the fact that you seem to enjoy the Jeep with the current engine, I think the most prudent thing to do is to stick with the 2.5L. But first, you need to figure out if it’s any good.

Excessive blow-by through the dipstick or oil filler is usually a pretty good indicator that the piston rings are worn and the engine might be due for a rebuild. However, a plugged-up PCV valve could cause a similar problem. Clean or replace the PCV valve and hose. Make sure it’s operating properly. If it is, and the excessive blow-by persists, it’s time to go to the next step.

You’ll need a compression tester to check the condition of the cylinders, pistons, and rings, and to see if they are sealing properly. You can purchase an inexpensive cylinder compression tester from Harbor Freight ( Test each cylinder for compression and note the psi. A variation of 10 to 15 psi between cylinders is fairly normal, but if the variation hits or exceeds 20 psi you have a problem that should be addressed. You can double-check the low cylinders by pouring 1 teaspoon of engine oil into the spark plug hole and retesting. If the reading jumps up, the piston rings are worn. If it doesn’t, the problem is in the valvetrain. Don’t forget to clear the cylinders of oil before reinstalling the spark plugs.

If you diagnose the engine as being worn, you have some options. You can take your engine to the local rebuilder, or you can simply swap your engine out with a remanufactured long-block engine from a company such as ATK (

Any advice or tips would greatly be appreciated. As always, I love the magazine, and thank you for your time and help.Jeremy Pugh Via email

First and foremost, thank you for your service and all your efforts overseas! Without people like you, we wouldn’t be able to enjoy everything that we do here back at home.

Your axle swap idea is a sound one. Ideally, you should start with the 8.8-inch from a Ford Explorer. You can find them with disc brakes and 31-spline axleshafts. Companies such as Artec Industries (, Ballistic Fabrication (, and RuffStuff Specialties ( offer the weld-on suspension brackets needed to put the Ford 8.8-inch under your Jeep TJ Wrangler. If you have difficulty locating a Ford Explorer 8.8-inch or can’t perform the fabrication and welding needed to make the swap, East Coast Gear Supply ( offers Ford 8.8-inch Explorer rear axles complete with TJ brackets ready to bolt into your Jeep.

As for the front, you can install the sleeves, gussets and truss to keep your Dana 30 from bending. However, if it’s already bent, you’ll want to start with a fresh housing. These products will not straighten a bent axlehousing.

The Ford 8.8 and even the Dana 30 should serve your Jeep well with up to 35-inch tires if you drive sanely. Overly aggressive driving with a locker will put the Dana 30 ring-and-pinion and axleshaft steering U-joints at risk. Upping the tire size to 37-inch tires will be a bit of a gamble. You could keep the 8.8-inch and Dana 30 alive if you don’t drive aggressively, but you’ll have to be very careful. Stepping into 37-inch tires really requires much stronger axle assemblies. The 35-inch tires are about the maximum I would recommend with the 8.8-inch and Dana 30 axles. The additional leverage and weight of the 37-inch tires will eventually take its toll on the 8.8-inch and Dana 30 axle assemblies.

You see, I’m actually considering an Atlas 2-Speed transfer case with a 5:1 low-range ratio. This unit with shipping, plus driveshaft modifications will push $3,400, but it’s still cheaper and cleaner than any other options for gear reduction this low. Scott at Advanced Adapters estimates a crawl ratio of 78:1 with the 5:1 reduction Atlas and 4.10 ring-and-pinion. My AX5 transmission and clutch are newly rebuilt, so replacing the AX5 with an older granny First gear transmission of questionable condition, plus sucking down the cost and calisthenics of adapters, and any unknowns make me moody.

Which brings us to my question. The additional torque with the Atlas added into the equation would greatly increase stress down steam of the transfer case to every other component including the stock Dana 30 vacuum disconnect axle, which my soul loves and will not part with. Yes, I want to be buried with it. I like it that much. Will this cataclysm of torque brutalize my beloved disconnect axle with the Air Locker engaged or disengaged for that matter? If so, then I’ll leave the little buffalo as is, and satisfy my off-road cravings by reading your magazine twice as often.

I’d murder the devil in his sleep for more crawling torque at times when slowing down can actually reduce the possibility of breakage. That said, I grew up in Sacramento, and ran the Rubicon from 1969 through 1972. That four years made up for every rotten thing I’d done up until that point in my life. I’d like to think I’ve gotten the rottenness and the rocks mostly out of my system, hence the modest engine and stock tires. Thank you for a superb magazine. The tech info throughout is a gold mine and the Your Jeep question and answer section is my favorite, a lasting treasure.Reg Jones Via email

Given the tire size you are running with no plans of significantly increasing the tire diameter, I think you could very easily keep the high-pinion disconnect Dana 30 alive with a 5:1 low range transfer case. If you had the itch to upgrade the Dana 30, you could swap most of the guts of your disconnect Dana 30 into a junkyard non-disconnect high-pinion XJ Dana 30. It’s a fairly simple swap, but it does require some basic cutting and welding. The XJ suspension brackets will need to be removed from the housing and new leaf spring perches will need to be welded to the axletubes. This swap would get you a sturdier axlehousing and a less problematic 4x4 shifting system. If you are worried about the factory axleshaft strength, you could upgrade to some RCV Performance ( CV-style axleshafts. They are significantly stronger than the OE U-jointed axleshafts and will fit in both your disconnect-style axlehousing (sans disconnect) and the non-disconnect XJ high-pinion Dana 30 axlehousing.

Recently, I started breathing life into the old plan, only to discover that finding a replacement Cherokee with similar specs and in good condition is quite difficult. I could use some help evaluating some alternate specs. At this point, my plan is to look for a ‘91 or newer Cherokee with a 4.0L HO engine. The basic build includes Dana 44 axles with electric lockers front and rear, 31- or 33-inch all-terrain tires that are 10.5 inches wide, fender flares and a lift as required, a winch bumper with an 8,000- or 10,000-pound winch, and a rear tire carrier bumper. How well does the Cherokee ABS system perform on- and off-road and how prone to failure is it? What type of problems might I have with the airbags, especially if I install a winch bumper and winch and possibly flat tow with a tow bar attached to the bumper? Considering that I have a potential donor vehicle in my driveway and a spare rebuilt AX15 and NP231HD in my basement, what will be required to swap an automatic transmission for a manual transmission? Will some years and transmissions be easier to swap out than others and what years are likely to be the most reliable?

A critical consideration is, when completed, the vehicle must be able to reliably pass Massachusetts annual inspection. Due to the age of the Jeep (pre-’03 model) this will be a safety-only inspection with no port scanning. However, one item that is checked is dash warning lights. If a warning light is on, including ABS, airbag, or any other light, this is an immediate fail. Any help you can offer will be appreciated.Doug East Wareham, MA

The ’91-’01 Jeep XJ Cherokee is a great platform to build from. Of those, the ’97-’01 XJ is the most desirable. It features several chassis and interior improvements and updates over the ’96-and-earlier models. The four-door model is usually preferred over the two-door model. The two extra doorframes further stiffen the chassis, and four-door models were more popular so they are easier to find than the two-doors. If you prefer a manual transmission, you’ll be far better off finding an XJ that already has one. Swapping out the automatic for a manual transmission will also require an ECU swap. Ultimately, it’s just not a cost-effective conversion since there are XJ Cherokees available with a factory manual transmission. An ’00-’01 model XJ with the NV3550 five-speed manual would be a real gem if you can find it. The NV3550 is more durable than the AX15 found in pre-’00 XJs. If you decide to stick with the automatic, the AW4 four-speed is one of the best automatic transmissions ever offered in a Jeep. An XJ with a 4.0L inline-six engine backed up with either the NV3550 manual or AW4 automatic is easily good for 250,000 miles or more if properly maintained.

The XJ antilock braking and airbag systems are far less problematic than what can be found in many of the other 4x4s available during the ’90s and early ’00s. You shouldn’t have any issues with your planned modifications. However, keep in mind that the Dana 44 axles you plan to swap in will require the correct tone rings and sensors for the ABS system to function properly.

You can fit 15-inch-diameter wheels on your JK, but the backspacing measurement (not the offset) will be critical to clear the brake calipers and steering knuckles. You will need a maximum of 3.75 inches of backspacing to fit the 15-inch wheels. A backspacing of 3.25 inches or 3.50 inches will work fine too. A backspacing measurement of anything less than 3.75 will work, but keep in mind that the less backspacing you have, the more the tires will stick outside the fenders. Also, less backspacing will increase the scrub radius on any 4x4, which can lead to handling issues. Moderation will be key, so don’t go overboard with too little backspacing.

Removing the track bars on your leaf-sprung YJ will increase articulation and give the front and rear suspension the ability to move more freely. You’ve likely noticed that the Jeep rides smoother on- and off-road. One possible side effect of removing the front track bar will be bumpsteer, which can make the Jeep a handful at higher speeds over larger bumps. The amount of bumpsteer you feel will depend on the lift height, if the Jeep has a drop pitman arm, and the softness of the leaf springs and shocks. The front track bar is designed to keep bumpsteer in check, but if you don’t notice any significant bumpsteer without the track bar, you should be good to go. However, suspension modification laws vary state by state, so you’ll want to look into your local laws before throwing the track bars in the garbage.

16 Inch Rubber Wheels

The 2.8L 60-degree GM V-6 found in the early Cherokee models has never been known for being a powerhouse or a pillar of reliability. It was so bad in fact, that GM developed and offered the 3.4L 60-dregree V-6 crate engine as a direct replacement for the 2.8L. The wildly popular and reliable GM 4.3L V-6 will not bolt in place of the 2.8L. Unfortunately, the 3.4L crate engine has long since been discontinued. If you’re doing it on the cheap, you might see if you can get your hands on a rebuilt 3.4L. Although, if your engine is still running strong, you could make some significant performance gains by matching the axle gear ratio to the 32-inch tires. Your Jeep should have come with 3.55:1 ratio axle gears. A switch to 4.10 or 4.56 gears would perk up on- and off-road performance significantly. Many different companies offer aftermarket ring-and-pinion gear sets and install kits for your axles. A junkyard upgrade is also a possibility. Some four-cylinder XJ Cherokees came with 4.10 axle gears from the factory. If you can find them, you could simply bolt these 4.10-geared axles in place of yours.

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