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30 Top Tech Questions

Classic 4x4 Pickup
JP Staff | Writer
Posted June 1, 2012

Got Jeep? Here answers

Nobody knows it all. If you’ve got a Jeep, then you’ve probably asked several of these questions at one point in time. How are we so sure? ’Cause we’ve answered them a whole mess of times. Are we complaining? Heck no—everybody has to start somewhere. The more time we’re asked questions like these, the more new Jeepers are entering the fray. So, happily, here are the answers to the top 30 tech questions we’re asked on a daily basis.

Q My Jeep needs a new engine. What engine should I swap in its place?

A Again, here’s one of those loaded questions that really depends on what drivetrain your Jeep came with, whether you plan on retaining your factory transmission, and a host of other factors. But to play it simple, we’ll just look at only engines for a moment and the aftermarket support in place for each.

For starters, it’s hard to argue the cost, power, reliability, and ease of a small-block Chevy swap. Sorry Chevy haters, but they’re simply the cheapest and easiest. The small-block Chevy has been produced forever and you can’t hit any junkyard, swap meet, or online venue forum without tripping over oodles of good, usable candidates. The only downside to the traditional small-block is that most came from the factory with carburetors. However, nowadays you’re almost as likely to trip over a TBI (or even TPI or Vortec) 5.0L or 5.7L as you are an older carbureted version. And every aftermarket company in the world makes components to slam it, adapt it, wire it, and fire it in just about any chassis. Old-school carbureted small-blocks work well in everything from CJs to Willys wagons and trucks, FSJ pickups, Wagoneer, and Cherokees, and almost any other Jeep model.

Rapidly closing the gap in popularity are newer Gen III/Gen IV GM engines, including the 4.8L, 5.3L, 6.0L, and 6.2L truck engines, as well as the 5.7L, 6.0L, and 6.2L LS engines from the Camaro, Corvette, and other performance car lines. Sorry, but the 7.0L LS-7 and supercharged 6.2L LSA and LS-9 offerings are nowhere near affordable yet. However, you can often find a take-out 5.3L with harness and sometimes the electronic overdrive 4L65E transmission for anywhere between $500 and $1,000. The 6.0L, 6.2L, and aluminum LS engines fetch more, but offer more power and/or lighter weight. The 5.3L will put out between 285-315hp depending on year and model and will knock down some seriously impressive mileage numbers. The nice thing about the Gen III/Gen IV engines is they’re newer than many late-model Wrangler vehicles, which makes a smog-legal swap a possibility.

Finally, let’s not forget the smaller stuff for the vintage crowd. It’s hard to go wrong with a Chevy 3.8L/4.3L V-6 or a Buick 3.8L/231 even-fire/ 231 or 225 odd-fire V-6. The Chevy versions are nice because they accept standard Chevy motor mounts and bellhousings, while the Buicks have front-mounted distributors for firewall clearance in tight four-cylinder Willys engine bays.

Light on Speed
Q I just got finished installing some flush-mount LED taillights and now my turn signal blinks way too fast. Did I break something or install them incorrectly?

A You didn’t break anything, and odds are really good that since a fuse didn’t pop, you’ve installed the lights correctly. What you are seeing is actually a “built-in” feature of your Jeep and many other automobiles. Most people don’t walk around the vehicle inspecting to ensure their lights are all working correctly, so it was decided to add this feature to alert a driver that a bulb is out on the vehicle. On the road, if you see a blinker on one end of the vehicle blinking faster than it should, the corresponding light on the other end will be out. It is called the “black out bulb” feature (BOB for short).

Fortunately, BOB is a part of your flasher module which, as we all know, is easy to swap out or change. We won’t get into the change of load on electromagnetic function here. We also won’t bore you with the way we used to open up flasher modules and cut trace wires on circuit boards or solder tiny relays onto them. Today, fixing your fast-flashing Jeep is as easy as going to your local parts store and getting a new flasher. Due to the proliferation of LED lights into the marketplace, most flashers no longer have a BOB function. Just look for the “LED” printed on the end of the flasher as shown in the picture and swap your old one out.

Cold and Crispy
Q I have heard that in my TJ if I run the heater on the highest setting it can cause a fire. Is that true? How do I avoid burning my Jeep? I’d like to be warm again in the winter—but not that warm!

A While we haven’t actually seen a Jeep catch fire from HVAC wiring, we have seen smoke coming out of the dash of a few of them.

The root cause is wear in the blower motor. As the motor wears, it draws more amperage. As it draws more amperage, the wiring in the dash heats up trying to pass more current than it was designed for. It’s a brutal cycle that keeps feeding on itself until your speed resistor dies, your wiring and/or switch in the dash melts and falls apart, or the blower motor just stops working. In the past, we have wired relays into the system only to see them melt again.

In “Jeep Fire Prevention,” (Oct. ’07), we put a series of relays in the system to take the heat out of the switch. We measured the temp of the switch before the modifications at 122 degrees, and you can see how we fixed it here: prevention/index.html

Then, in “Safe Heat,” (May ’12), we had to do it again, since the original fix only lasted for that amount of time, eventually melting another switch irreparably. By then, we’d learned more about the problem and how to fix it.

High Lock
Q I have a Rubicon and the lockers are great, but low range is no good for mud or sand. Can I modify my Jeep so that I can engage the lockers anytime I want to and not just in low range?

A Yes, it is totally doable. On a TJ, first pull the center stack in your dash off and gain access to the rear of the locker switches. Then, for the ’03 and ’04 Rubicon, ground the red wire with the white stripe. For the ’05 and ’06 models, you need to ground the violet wire with the orange stripe. Grounding the wires fools the switch into thinking the Jeep is in low range. If you have an ’07-or-up Wrangler Rubicon it is possible to fool the computer into thinking it is in low range, but you have to start jumping wires between pins on the computer. The exact procedure can vary depending on what year your Jeep is, and we simply don’t have the space here to cover it all. Beyond that, if you screw something up, it is likely damage to one or more computers in your JK will probably be the result. And, if that wasn’t enough, the Jeep most likely will realize at 18 mph that you aren’t in low range and trip a code that your dealer can see (which might affect your warranty). The safe way to do it is to pick up an aftermarket tuner that offers this function.

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