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4 Wheel Off Road Jeep Mods - Make It Better - Jeeps 2003

Posted in Product Reviews on March 1, 2003 Comment (0)
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Photographers: John WhiteJohn Sweeney

Jeeps are not money pits. On the contrary. Spending time and money on any Jeep is an investment in fun and freedom. It can bring you closer to your friends and family and keep you out of trouble because you'll always be in the garage or lying in the driveway. When you're done, your Jeep can take you as close to, or as far away from civilization as you want to get. Perhaps the hardest part of modifying a Jeep is knowing what to do next. We get a lot of questions from readers who want to run their buildup plans by us to get our feedback. We find that we keep recommending similar steps and a lot of the same sources. So if you've got an old Jeep you're working on, or just rolled off the lot in a new '03, we've got 10 more mods that you should add to your list.

Remove The TopThis is the cheapest modification we could think of. It's free. If you own a CJ that has never had the top off you should be ashamed of yourself. People who have just bought an '03 Rubicon are only allowed a grace period of two months before they must go topless. We don't care if there is still snow on the ground. If you own a Jeep and don't even have a top for it-you're our kind of guy.

Engine SwapWe've concluded from all the letters you've sent us that the only Jeep engines you consider keeping in your Jeep are the 4.0L I-6 or the Mopar V-8s. The rest of you want to swap your Jeep engine for a small-block Chevy, Ford, or even Buick and Chevy V-6. If you need help selecting which engine is right for your budget, read through the "Knowledge Base" section of Novak Enterprises' (877/602-1500, Web site. One engine swap you won't see there is a new Mopar Performance 435hp 402 crate engine into a Grand Cherokee. In fact somebody out there better be working on a twin-turbo Porsche Cayenne-killer with this engine to defend the honor of Jeep owners everywhere! The engine will cost you about $4,600 (see your local Mopar Performance dealer or and will bolt in place of a tired 5.2L. If you're resourceful enough you might even be able to adapt the factory EFI to run it. It might be hard to get it past your local emissions test though.

Transmission SwapThere are two reasons to swap transmissions. Your engine is too powerful for whatever you have or to get a better selection of gearing. When selecting a transmission, pay close attention to rear driveshaft length. By the time you add up the length of the new transmission and the adapter to mate it to the transfer case, you may only have room for a 10-inch driveshaft. Spend some time under your Jeep with a tape measurer before you head to the junkyard. Plus it's a good idea to order Advance Adapters (800/350-2223, free buyer's guide to get an idea of what components will work together.

Slip-Yoke EliminatorJeep requested that New Venture Gear move the slip from the driveshaft to the transfer case so that it could save assembly time and money. Not to worry though, because the aftermarket has kits to convert your transfer case to a bolt-on style yoke and give you back 3-4 inches of driveshaft. Kits like Currie Enterprises' (714/528-6957, cut, drill, and tap the original shaft and bolt a flange on that you can adapt a yoke to. Those available from Advance Adapters (800/350-2223,, TeraFlex (801/256-9897,, and Tom Woods (877/4XSHAFT, supply a new output shaft and often a new tailshaft housing. When selecting a kit you might want to consider upgrading the rear output shaft to a 32-spline piece sold by JB Conversions (337/625-2379, instead of the stock 27-spline piece. You'll need to plan to spend another $200-$300 for a 4-inch-longer double-cardan driveshaft too.

Spring-Over SuspensionA spring-over axle suspension conversion takes your axles that are slung between the leaf springs and frame and moves them under the springs. This requires relocating the spring perches on the axletube, relocating the shock mounts, fixing the steering interference issues, and finding a way to deal with the axlewrap that almost always results. You end up with more than 5 inches of lift; more flex, and better ground clearance. It's the only way to go if you own a Jeep and plan to run 35-inch-or-taller tires. Leaf-spring suspensions are relatively simple, but make sure to double-check your work before you cut anything off or weld anything on. And please, if you're not a great welder, have someone who is inspect (or do) your work.

Bolt-On Engine UpgradesIf you plan on keeping your engine then it can benefit from some easy bolt-ons that you can buy without going broke. The first step we recommend is adding a performance exhaust. While it may free up a little more power, you're buying the sound more than anything because most factory systems are very good on newer Jeeps. Be careful that you're not replacing a stainless steel system with an exhaust made of inferior metal. Next you'll want to add a larger-capacity air filter and take out as many restrictions between the cool outside air and the throttle body. Beyond that it's time to get serious. Buy a copy of the Mopar Performance catalog and turn to the Jeep section and consider camshaft swaps, larger valves, headers, and even some cylinder head work. Tie it all together by having your fuel injection modified by a shop that can tailor the EFI to your engine, and start burning rubber.

NV 241J Rock-Trac 4:1The NV 241J Rock-Trac is arguably the best transfer case to ever come in a Jeep. Its 4:1 low-range, reinforced housing, and bolt-on yokes make it an Atlas competitor, and at price of $1,600 from JB Conversions (337/625-2379,, it's more affordable too. Right now the applications it will work with are limited to Jeep and Dodge transmissions with 23-spline output shafts. But it is a direct swap into any Jeep with an NV231, and it's a lot stronger too.

Power SteeringOlder off-road Jeeps with big tires need power steering. Sure, you can Hulk Hogan the steering wheel with a set of 35x12.50s around town, but get out on the trail and engage a front locker and even the Hulkster will be down for the count after 100 yards. A power-steering conversion requires a power-steering box and pump with the proper mounts, linkage, and plumbing. Again we'll refer you back to Advance Adapters (800/350-2223, for the basic kit.

Stronger AxlesIt's been said that to build a Jeep you keep the body and throw everything else away. By today's rockcrawling competition standards that's true, but none of you should feel like you can't have fun on the trail unless you have 1-ton axles under your Jeep. We know stock axles have their limits, but we've seen them work a long time in some applications. We already know the factors that lead to axle failure. They are: traction (tire size, lockers, terrain), torque (engine power times gear reduction), and vehicle weight. Increase any or all of those things and you are going to break stuff-and it's probably going to be an axle. If you're a recreational user with tires less than 35 inches tall, we recommend you wait until you do break something before you throw money at the Jeep. If you get the urge to swap axles we think that Dana 44s front and rear will give you the best value for your dollar-especially if you don't have to have them custom made. If and when you start breaking Dana 44 parts you always have the option to upgrade them with stronger axleshafts, chromoly U-joints, and locking differentials.

KnowledgeThere must be a million books written about Jeeps. The best that you can hope for is to gather a reference library of information on your particular year and model. We've found a factory service manual to be the best place to start. Novak Enterprises (877/602-1500, has reprints available for most of the older stuff, and the late-model service manuals should be available from your local Jeep dealer. Of course we expect you to save every copy of 4-Wheel & Off-Road you get, because you never know when we might spring a Jeep pop-quiz on you.


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