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Top Jeep Tech Questions - Common Queries

Custom Jeep Buggy Wheeling
Verne Simons
| Senior Editor, Jp
Posted February 19, 2014

Questions that we get a lot

Believe it or not, the editorial staff of Jp possesses superhero-like superpowers— but they are not as useful as being able to stop a speeding train, deflect bullets, fly, or even prevent crime (above possibly screaming “Stop thief!” and firing off a few well-placed rounds). Our secret powers consist of an extreme knowledge of Jeeps, Jeep problems, and Jeep fixes—all this is the result of being obsessed with Jeeps for as long as we can remember. Sounds fancy, huh? Yeah, it is, and the ladies love it. Um, not really. Also these powers have limits, and we occasionally hit them when we get questions from readers, but luckily for you, we also like learning and sharing what we learn. Having said all that, we love getting questions about Jeeps. Some questions are more of a challenge than others. Some we get over and over again, but that does not meant that they are not good questions. That’s the focus of this article, answering all those common questions that we frequently get and that need answers. Please keep the questions coming!

To Regear or Not To Regear
Hey, ya’ll at Jp, I just bought a Jeep and added a lift kit and big ol’ tars (that’s tires to you and me). Now my Jeep is a pig and I can’t go up hills on the highway without rowin’ through the gears like a raccoon washin’ crawdaddys. I’ve heard I should regear my Jeep. What’s that mean, and do I have to?

Adding larger tires to your Jeep changes the overall drive ratio of the vehicle. The easiest way to rectify this is by regearing the axles. Unfortunately, regearing properly requires lots of know-how and specialized tools. Your money is well spent regearing, and you are better off not trying to make this upgrade a DIY affair.

We get this question all the time, and heck, we all used to be on the other side of this question at one point or another back in our respective “first Jeep” fledgling times. The fact is adding larger tires to your Jeep makes a mechanical change in how it works. Why? Well, the larger tire takes a greater distance to make one full revolution because the outside diameter of the taller tire is also larger than its stock counterpart. The easiest thing is to change the axle ratios in your Jeeps axles back to close to the factory ratio with these larger tires. Here is the math for figuring out your new gear ratio: (new tire size / old tire size) x original axle ratio = new ratio. For example, if you bought a new JK and wanted to add some 35-inch tires, you will want to regear. Here is the math: (35/29) x 3.21= 3.874. This means we would be good with about 4.10s. If the Jeep is a crawler or used for towing, you may want to go a little lower than that, such as 4.56.

Do you have to regear? Nope, but it’s the easiest way to improve fuel economy, regain that lost pep, and your sanity. Also, if the change on-road is not enough to convince you, then the benefits off-road should do it. Off-road you will enjoy better crawling, more usable power, and less wear on parts like the clutch or auto transmission.

Thank Pete
I say good day, Jp editorial staff. What is the largest tire I can fit on my Jeep with X inches of lift?

We’ve been lifting Jeeps here at Jp for years and we have a pretty good knowledge base regarding what tires will fit with what amount of lift, proper bumpstopage, and maybe a little (or a lot) of fender trimming. Use Google to find a story called “What Hits, What Fits” for the answer to your tire size lift question.

Well, thanks to Pete and the experience of the rest of the Jp staff over the years, the answer is pretty easy to find. Either take the analog route and dig up your March ’11 issue of Jp and look for “What Hits, What Fits,” or, if you have any idea what the interweb is, just get on your local Google machine and search for “Jp magazine what hits, what fits.” Information on what tires will fit with what amount of lift for basically all Jeeps ever produced will come up. Having said all that, if your YJ has 500,000 miles, the springs may have sagged a touch and you may want to err on the side of a smaller tire. If your low-mileage cream puff TJ has a brand new 4-inch lift, then you are probably safe running those 33s.

First Things First
Hi Jp, what do I do first, spend my cash on suspension lift and bigger tires, or get a winch and body armor?

Hear us now and believe us later, you can pretty easily screw up the rockers of a nearly-stock Jeep. Having good rocker armor is definitely one of the first upgrades you should make to your Jeep. Furthermore, rocker guards are way easier to install when your rockers aren’t all beat up.

We get this question all the time, and honestly, it is one of those questions that really depends on what you want to do with your Jeep. Planning on going expeditioning 1,000 miles from nowhere by yourself? First, that’s a bad idea, but if you have to, you’d better get yourself a reliable winch, tree strap, a Pull Pall land anchor, water, food, fuel, and so forth. Are you going out to hit the local mud hole back east with all your pals on the weekend? Add your lift and tires—and towhooks. Honestly, regardless of what you are doing, rocker guards should be near the top of the list. We’ve damaged rockers on stock and near-stock Jeeps more than we care to admit. It’s a vulnerable, difficult-to-repair area on most Jeeps, and a little insurance is worth the price of admission.

Yearning for More Go
Yo, Jp, what up? After bolting all kinds of heavy ghetto armor to my Jeep, it’s acting sluggish and I’ve been hoping I can add 200-300 horsepower. Oh, and I am broke! What can I do to get the revs up without spendin’ all my lettuce homies?

Umm…word up! Your Jeep is probably not going to pick up 200-300 horsepower regardless of how much money you toss at it—unless it has a tired four-cylinder and your upgrades include swapping it for a built 401 V-8. We are generally all for upgrading to a free-flowing air intake system and exhaust, and maybe an electronic tuner if your Jeep can use one, but much beyond that, things get expensive and complicated. If you are coming at Jeeps from the hot rod world and speak the lingo of engine building, cam swaps, and raising compression, then you probably know how to make more horsepower. Good for you. If you don’t, you can easily learn about making internal improvements to your Jeep’s engine, but in the end you may not be helping your Jeep work off-road. Why? Well, the vast majority of Jeeps don’t ever get used at or near their red lines where maximum horsepower is made. What and we all want is more torque and more specifically usable torque. That is the grunt you feel in the seat when your Jeep climbs. Many hot rod parts are built to get maximum horsepower at a higher RPM, not maximum torque at a lower RPM. Generally, Jeepers should be interested in an engine that makes maximum torque at 1,500-3,000 RPM while burning low-octane fuel.

Another option is to force-feed your Jeep’s engine with more air with the help of a turbo or supercharger, and there are a few options for some of the Jeep engines out there. Some Jeep engines are strong enough to handle forced induction, while others are not. If you have an AMC-based I-6, V-8 or four-cylinder, the bottom end can probably handle forced induction. The 3.8L V-6 found in JKs, not so much. Either way, turbo and supercharger systems are not inexpensive and generally require use of high-octane fuel. Nitrous? Well, yeah, that will boost horsepower for a brief time at full throttle and high RPMs, and thus is probably not really appropriate for a trail rig or crawler.


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