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Answers to All your Jeep questions

Posted in Features on September 15, 2015
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Photographers: Owners

Grand Ambition

I have a '97 Grand Cherokee 4.0L Limited with all the usual extras on it. I want to upgrade the rear axle or swap it out. Currently, I'm running 32-inch tires with a 3-inch homemade lift. The steering and brakes have already been changed to WJ parts, and the front axle has been swapped out for a high-pinion Dana 30 from an XJ. I intend to eventually run 33 or 35-inch tires with 3 or 4 inches of lift. Should I stay with the Dana 35 and upgrade it (bearing in mind all the write ups that slight this axle), or do I use a Chevy 10-bolt (8 1/2-inch ring gear with factory limited slip, disc brakes, 3-inch axle tubes, and 29-spline 'shafts), or do I go with a WJ 44a axle with the factory limited slip or the V-8 version with the Vari-Lok? Also, do you know if a front Vari-Lok from the low-pinion Dana 30 WJ will fit a high-pinion Dana 30 XJ? I know there will be some fabrication and regearing involved, but in your opinion, which would be the best route? The kind of driving over here is mainly gravel, mud, grass-covered hills, and more mud, but no rockcrawling. It's fairly tame compared to what you guys have to play with in the States. The only reason I listed these particular axles is because I have them and don't have wrecking yards nearby, so I cannot go searching for others. I could get Land Rover axles but they are made of cast cheese (crap, in other words).
Ged
Derbyshire, England

Unfortunately, none of these axles are what I would consider heavy-duty. Given these choices, I think your most logical option is to go with the WJ 44a (aluminum) Dana 44 axle. It should hold up fine behind the 4.0L and 33 to 35-inch tires, if you drive sanely, same as your front axle. If nothing else, at least there are a few aftermarket upgrades available for the WJ Dana 44a.

Putting a Vari-Lok in your front Dana 30 won't be worth the effort or cost. It will require custom-made axleshafts. It would be more cost effective to simply purchase and install an aftermarket limited slip or locker. There are many to choose from for the XJ Dana 30.

Oiled 4.0L

What is the best engine oil and filter combo for the 4.0L engine in my lifted daily driven '02 Jeep TJ?
Guillaume Poirier
Via email

The Jeep 4.0L inline-six engine was based on a design that was more than 50 years old. The 4.0L is an extremely durable and well-tested mill. It would likely run fine on almost any engine oil. However, the viscosity of the oil recommended for your 4.0L is dependent on the ambient temperature. For temperatures that range from 0 to above 100 degrees, you'll want to use 10W-30 in your 4.0L. If you are exclusively operating your Jeep in temperatures below 32 degrees, then you'll want to use a 5W-30 oil. The thinner oil will allow for easier startup when the engine is cold. The lower viscosity oil will also circulate more freely to the vital engine components in the freezing temps before the engine warms up.

Many people prefer more expensive synthetic oils for their improved performance, superior lubricity, and longer oil-change intervals. This is all well and good on a street-driven engine. However, something that is often overlooked by the synthetic oil fan club is that Jeeps and their engines are subjected to off-road use and a lot of dirt. Dirty oil, regardless of whether it's synthetic or conventional causes engine wear. Extending oil change intervals exacerbates the problem. For a Jeep engine that sees off-road use, perhaps the most important thing is to make sure the oil is clean. Synthetic oils will certainly minimize engine wear, but you'll still need to follow regular recommended oil change intervals if your Jeep sees a lot of dirt. This sort of eliminates one of the advantages of synthetic oil, but if you can accept the cost, synthetics are still a good choice.

Now, how often you should change your oil will depend on what the manufacturer suggests. For your 4.0L, there is an A and B maintenance schedule that dictates an oil change every 6,000 or 3,000 miles, respectively, depending on how the vehicle is used. You should follow schedule B if you regularly operate your Jeep in any of the following conditions:

  • Day or night temperatures below 32 degrees Fahrenheit
  • Stop and go driving
  • Excessive engine idling
  • Driving in dusty conditions
  • Short trips of less than 10 miles
  • More than 50 percent of your driving is at sustained high speeds during hot weather, above 90 degrees
  • Trailer towing
  • Taxi, police, or delivery service (commercial service)
  • Off-road or desert driving
  • If equipped for and operated with E-85 (ethanol) fuel

As for oil filters, they are not all created equal. Having seen a few different brands of filters cut apart, I have become fond of Wix (wixfilters.com) and Napa (napaonline.com) Gold filters. These two brands seem to be made with higher quality components and have more filter surface area than some of the other brands available. I'm sure there are other filters that are just as good or better, but those brands are a good cost and quality compromise. Ultimately, regular oil changes and making sure the oil is free of contaminants will increase the life of your engine much more than selecting the proper oil filter.

Chattering Driveline

I have a '94 YJ with a Ford 5.0L. The engine is mated to an NP435 manual transmission and an NP203/205 doubler transfer case. The front axle is a high-pinion Dana 60 and the rear axle is a 14-bolt. The transmission and transfer cases have been rebuilt. The problem is that I have a loud gear chatter while coasting. If I put the rear output in Neutral and only drive the front wheels, there is no chatter. I used an angle finder and it shows the rear driveshaft is at 32 degrees. The rear axle is tilted up to just under the rear output at the transfer case. This chatter is driving me crazy enough to want to pull out the doubler.
Clayton Thomas
Via email

It sounds as though you may have added the doubler without changing the rear pinion angle, which could cause the problem you are describing. A 32-degree driveshaft angle is pretty steep if it's the actual working angle of the upper driveshaft joint. The low-slung pinion on the 14-bolt certainly isn't helping your situation. I suspect the chatter is coming from the rear driveshaft. I assume you have a double-cardan CV-style rear driveshaft. If you don't, then your driveshaft angles are way off and you'll need one. You'll need to measure the angle on the rear output yoke and the driveshaft angle to calculate the actual U-joint working angle. In most cases, the rear output yoke is either at 0 degrees or angled downward slightly a few degrees. But first you need to make sure the rear pinion angle is correct. With a CV-style driveshaft, the rear axle yoke should be pointed directly at the rear output yoke on the transfer case and inline with the driveshaft. It can be aimed down a degree or two to compensate for axle wrap if you have a leaf spring suspension. If all the angles line up and you still have a 32-degree U-joint angle, you're going to have to lower the transfer case and or lower the suspension. This will help improve the driveshaft angles and make your Jeep more streetable. A U-joint operating angle around 15 degrees is much more ideal for a street-driven CV jointed driveshaft. The maximum angle for a typical CV joint is around 30 degrees, meaning it should only reach that angle when the suspension is fully extended. Some modified aftermarket CV joints can extend past this angle; however, their working angle is still limited to less than 30 degrees. For more info on acceptable angles and other driveshaft tech, check out Tom Wood's Custom Drive Shafts (4xshaft.com).

Winch Mount Wonderer

I have been following "Garage Project GPW" in several issues of Jp while rebuilding a '65 CJ-5. I would like to know where you sourced the winch plate.
Kenny Cantwell
Via email

Unfortunately, the winch plate and bumper combo on the Garage Project GPW is not an off-the-shelf part. I built it from scratch. I actually had an old plate-style rocker guard for a CJ-8 laying in my side yard that I cut up and used for the main structure. I've added gussets, reinforced it in several areas, and drilled holes to accept a Warn 8274 foot-forward winch that I picked up from a friend. Warn (warn.com) does offer some foot-forward winch mounts that could be adapted to the front bumper of an early CJ. Take a look at Warn part numbers 11078 and 11310. They may provide a good starting point for your own custom bumper.

Rotten Frame Repair

My Jeep has a bad case of frame rot. My tub and other parts are in great shape, though. I don't have the budget to just buy a new Jeep. What route should I take? I was searching online and to get the patch kits I need it would cost about the same price as a clean used frame. I plan on tackling the project this summer. What would be stronger and more valuable as far as resale in the distant future? What are the advantages and disadvantages of each choice?
Josh O'Hara
Fairhaven, Massachusetts

Frame and body rot can be a big problem in the rustbelt. Repairing a frame involves cutting out the damaged areas and welding in replacement patch panels. This requires a good amount of fabrication and welding skill to be done properly. Fortunately, Auto Rust Technicians (autorust.com) offers many different Safe-T-Cap frame repair panels for popular Jeep models built from '67 to '03. The company can also perform the work for you. If several areas of your frame are in bad shape, it may be more cost effective to simply replace the whole frame, if you can find a suitable replacement. Frames at the local wrecking yards will likely have the same rust problems as your frame, so it's best to ship one in from the Southwest if at all possible. Companies such as Collins Bros. Jeep (collinsbrosjeep.com) specialize in new and used Jeep parts. The company may be able to help you locate a frame if you decide to go this route.

As for resale, again, it will depend on how many patch panels your frame needs. A properly coated rust-free stock frame will certainly help you get top-dollar for your Jeep. However, if you spend the next 5-10 years driving the Jeep on salted winter roads, you'll likely be in the same predicament all over again, regardless of if you repair or replace your frame. They key is to keep the frame clean and coated. You don't want salted slush to stay on the frame overnight. It's best to hose it off with fresh water as often as possible. Or better yet, don't drive the Jeep in winter. This may not be a viable option, though.

Shadetree Mechanic Training

I have a few Jeeps, and I have to pay someone to do certain kinds of work because I'm not a mechanic. I've always wanted to be able to do mechanical work (pulling engines, axles, and so on) but I don't know where or how to learn these things. Any suggestions?
Doug
Via email

Of course Jp is a great place for build and wrenching info on your Jeep, but the best place to get started is on your Jeep and the best time to start is now. Get your hands on a factory service manual and begin with the small stuff to familiarize yourself with the components in your Jeep. Perform an oil change, service the differentials, transmission, and transfer case. From there you can move into wheel and axle bearings, brake jobs, U-joint replacement, and so on. You can also enroll in automotive night classes at a local college. Search for how-to videos on YouTube. You don't need a massive amount of tools for most job; You can purchase them as you go. What's most important is that you get in there and try. You may still need the assistance of a paid mechanic from time to time, but as you learn, you'll become more familiar with how all of the components on your Jeep function and what it takes to keep them working properly.

Top Question

I'm looking for some advice on a decent replacement soft top for my '04 Rubicon. My dad has a '97 Wrangler Sport. He buys used tops and has gone through three of them in 10 years. Would it be worth it to call the dealer and get a new one?
Lisa-Marie
Via email

Buying used tops is one way to save a few bucks. However, you have to realize you are often buying a used top that has already given up some of its life on another Jeep. The good news is that you have other options besides the Jeep dealer when searching for a quality soft top. If you are looking for factory materials, check out Bestop (bestop.com). The company builds the factory soft tops for Jeep. If your hardware and bows are in good shape, you can simply purchase the Replace-A-Top kit. This kit can save you some money by allowing you to reuse your hardware and bows. The included all-new fabric and windows replace your weathered parts. You have several material options. The heavier Sailcloth fabric is one of the best top materials you can buy.

Companies such as Rugged Ridge (ruggedridge.com), Smittybilt (smittybilt.com), and others also offer replacement Jeep tops as well.

Long and Short Of It

I just purchased my dream Jeep, a '06 Rubicon TJ. It has a 9,000-pound winch, a swing-away spare-tire carrier with dual gas cans, 29 1/2-inch Goodyear tires, a Radio Shack CB, an Optima YellowTop battery, and an unknown vintage wine cork plugging a hole in the firewall. Future plans include a daily 5-mile commute to work and exploring local trails like the Rubicon and Fordyce on 33-inch mud-terrain tires. Would you please educate me on the pros and cons of a short-arm versus a long-arm suspension lift? I respect your opinion because of your cumulative experiences and vast knowledge of all things Jeep (blatant butt kiss to get an answer).
John Toups
Reno, Nevada

Clearly I'm not immune to a proper butt kissing. The choice of going with a long-arm or short-arm suspension lift typically depends on several factors, including the Jeep model you are working with. On a daily-driven TJ Wrangler, it's acceptable to stick with a short-arm kit when lifting your Jeep less than 3 inches. Any more lift than this and the Jeep will not perform as well as it could on- or off-road. When you get into the taller lift heights, the increased angle on the shorter link arms can cause erratic on-road handling and instability on the trail. If you decide to go with a lift kit of more than 3 inches, I think you'll be happier with a long-arm suspension kit. The longer suspension arms will have less angle on them at static ride height and allow the axles to cycle more smoothly and predictably over rough terrain on- and off-road. Don't forget to add the proper steering and track bar corrections to match your chosen lift height.

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