Jeep Creep: Off-Road Jeep and Tech Questions Answered

Dec. 19, 2013 By Jim Brightly
In your Jeep Creep questions, please list your first and last names, your hometown, and your state/province/country, so that we can publish that information here. If you don’t provide this information, we may not be able to publish your question and answer. Don’t forget to be as complete as possible with the description of your Jeep and its problems, too. Send your Jeep questions to, Attn: Jeep Creep.

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PLEASE NOTE: Due to the lapse in Federal Government funding after the close of business September 30, 2013, NHTSA has been unable to process safety defect complaints in the usual manner. Consumers can continue to file complaints, but the complaints will not be evaluated by NHTSA staff in a timely manner. NHTSA’s monthly reports are still being delayed.

Down here in Florida it’s flat but sandy and muddy; deep mud through the Everglades and swamps, and soft sand along the beaches. It’s not like rock climbing out West where you can crawl slowly over rocks and dry waterfalls. It’s more like playing in the sand dunes. We need RPM, horsepower, and wheel spin. My Rubicon four-door Jeep just barely seems to have enough. I can slog through the mud and struggle through the deep sand, but I want something more. I want to play rather than worry about getting stuck! I’ve installed Chevy V8s in Jeeps, and that was a huge job. But I’m still thinking I might have to in order to play. I’m also thinking about a hemi. But either way it’s going to be a lot of time and money. Any advice?
Ron Veracruz
St. Petersburg, Florida

I know exactly what you mean, Ron. I’ve been running the mud bogs here in Arizona for the past few months and horsepower and wheel spin are definitely what are needed to win! Likewise with bowling in the dunes—horsepower and wheel spin. And even though my mud bogger has a Chevy 350 small block V8 in it, you might not need a V8 for your play time. Since you didn’t say what year your JK Unlimited is, I’m going to include information on Magnuson’s superchargers for both the 3.8L V6 and the later 3.6L V6. Also, the Rubicon you said you have has the more stout Dana 44 differentials and the stronger transfer case which should handle the added torque better than the less beefy models.

Magnuson ( has recently introduced a supercharger kit for the 2007-2011 Jeep Wrangler JK 3.8L. According to Magnuson’s literature, this kit has demonstrated a 33-percent increase in torque and 41-percent increase in horsepower. And all that torque is said to be available right off idle. Magnuson’s MP1320 TVS supercharger uses the latest design in Eaton’s line of Twin Vortices Series superchargers with their four-lobe, 160-degree high-helix rotors that provide increased air flow, have a wider operating range, and higher pressure capability while maintaining cooler operating temperatures and a quieter operation.

With this system, your Jeep Wrangler 3.8L can have more ponies while maintaining its everyday drivability. Whether you’re on the street or on a trail, you won’t have to wait for power. All of these benefits are achieved while using less engine power through a reduction in parasitic engine drag during cruising situations. These cruising losses are nearly eliminated, which the company says will give you near-stock fuel economy under normal driving conditions, and quick torque when you need it.

The system contains a cast aluminum high-velocity intake manifold, the MP 1320 TVS supercharger as well as all of the fittings, lines, belts and hardware needed. To really maximize the efficiency of this supercharger kit it is also available with an air-water intercooler system that includes the intercooler core, coolant circulation pump, coolant reservoir, and heat exchanger. Additionally, this supercharger system comes with all of the necessary tuning and fuel-system upgrades your Jeep will require to handle the boost this blower delivers. This includes new high-flow fuel injectors that retain all of the factory “push-lock” connectors and a Diablo Sport Trinity handheld programmer. Magnuson’s ECM recalibration ensures the proper adjustment of the air/fuel mixture and ignition timing settings to optimize the increased torque and horsepower of your Jeep while maintaining its street driving manners and fuel economy.

Again, since you didn’t mention your Jeep’s model year, while researching this question, I discovered that Magnuson will start shipping a similar supercharger system for the 2012-2014 Jeep Wrangler JK with the Pentastar 3.6L engine on January 17, 2014. This kit—according to Magnuson—has demonstrated a 40-percent increase in both torque and horsepower at just 6 psi of boost.

V8 versus V6?
I am curious about what engine to put in my ‘93 YJ? It’s my daily driver and it has a straight-six 4.0L and a three-speed auto tranny in it now. My Jeep is fully stock with 3.07 gears and it doesn’t seem to perform off-road like other Jeeps. I’d like to get better mileage but still want more power and better ability on the trails around here. What is the difference between a Vortec engine and a stock Chevy engine? I have found a couple SUVs for less than $2000 with V6 engines, which seem to be good deals. I was just looking to see and get some ideas about the price range. So can you tell me which to get: a Chevy 350 V8 or a Chevy 4.3L V6? And can you tell me what MPI and TBI mean?
Fred Palfrey
El Cajon, CA

Fred, a 3.07:1 ratio is terrible, especially with 33-inch tires! No wonder you can’t climb hills or have any hold back. Low gears are the only way to go if you want to go off-roading, but they’re not going to do your mileage any good and they’re expensive. Like I tell all my readers, if you want mileage, don’t buy a Jeep—buy a VW. Everything you do to a Jeep to improve its off-roading capability decreases its on-road capability. If you want to go Jeeping, you have to accept that. If not, sell it and buy a VW.

You have to change the gears in both ends. If you go to Randy’s website you can play with tire size versus gears to achieve the optimum RPM for the best performance on the highway. For instance: In my JK—knowing I have 35” tires—I played with the gear ratios and came up with either 4.56:1 or 4.88:1 to return the engine RPM to approximately the same as stock at 65 mph. 4.88 gears with 35” tires makes the engine RPM slightly—less than 200—higher than stock tires and gears. That’s what you can use a tachometer for. If you don’t have one, you can install an aftermarket unit easily (Summit Racing offers several different types, designs and RPM ranges). A tachometer is great for highway driving and can also really help you in off-road driving.

I strongly suggest you buy a Chilton Jeep Wrangler 1987-11 repair manual (it has a YJ on the cover). I wouldn’t buy one from another publisher unless it also includes wiring diagrams, which you’ll need.

If you get you a 4:1 low range for your transfer case, it will give you better off-road traction, much better hold-back on hills, and not change fuel mileage. You’ll really like having the deeper low range no matter what gears you end up with—both of my Jeeps have 4:1 transfer cases (Rubicons come from the factory with it).

Since you live in Southern California, Fred, I can understand why you want both mileage and performance. While I love the drivetrain in my 1982 CJ7—Chevy 350 V8 and TH350 automatic—it’s perfect for Arizona (I either trailer it to the trails or drive very short distances for the trails), its 60 mph top speed on the freeway and 12 to 14 mpg would not be ideal for SoCal. My engine is TBI (throttle body injection) which means there’s just one injector (very similar to a carburetor) and then the intake manifold sends the fuel to the cylinders. The advantage over carburetion is that there is no float to flood out; as long as the engine is running fuel is provided to the cylinders, and the onboard computer will attempt to modify the fuel/air mixture according to the altitude and atmospheric pressure.

MPI = multi-port injection. That’s where each cylinder has its own injector. The MPI is the better system of the two designs and the more efficient system. Chevy named their MPI engines the Vortec and they appear from 1995 to now. GM has improved the engines as smog laws become harder to meet, and mileage must also improve as efficiency is improved. Therefore, I recommend a Vortec 4.3 V6, and in California, the engine must be newer than the vehicle it is being placed in, and the smog system must match the engine. This has the performance of many V8s and the mileage potential of most V6s.

In addition to the 4.3, I suggest the GM 700R4 four-speed automatic, since it comes from the factory attached to most of the 4.3L V6s (or a later four-speed automatic transmission with an overdrive gear) with an adapter for your NP231 transfer case. That is, if you’re going to install deeper gears and taller tires for crawling over the more difficult trails—like Big Bear’s John Bull Trail.

No 4WD?
I want to buy a 1988 Jeep Cherokee. It looks clean and the price looks right. But I cannot find any information on this model. It has a fuel rail and is a straight six and auto. When I try to shift into 4-wheel nothing happens. No sound or tightening of the lever next to the shifter. I was told I had to put the selector into neutral first, and then put it into low or high 4 but still nothing. What can be wrong? The lever seems to not be attached to anything under the floor at the transfer case. It does look like an NP231 transfer case. Do you think it could be just the shifting rod?
Roy Valdez
Houston, TX

It sounds to me like the shifter has worked its pin loose, Roy. The linkage bushing was probably worn or bent and it let the link fall off or the lever’s nut worked loose.

Truck Steering
We have a 1984 Jeep J10 long-bed 4x4 pickup with tilt steering, automatic and a shifter on the column. We are trying to find a replacement steering column for it. Would any 1976-86 AMC CJ Jeep steering column work on this truck? It’s my son’s truck and he broke the column while trying to fix the ignition. We want to be sure we can get something that matches.
Ratha Cathew
Patterson, CA

Most CJ column parts will work and some from Chevy/GMC pickups. It’s called a Saginaw steering column because it was built at GM’s Saginaw parts plant. I suggest a trip to a few “pick your parts” lots in your area. However, I think you have a TH400 three-speed automatic transmission, not a three-speed. Some larger GM car models might also prove to be a proper donor vehicle for your steering column.

Smelly Smoke
I just got a 2000 Cherokee Sport with 243,000 km. Some oil is burning, and the smell is there, as well as black residue on the valve cover. Could it be the head gasket on the 4.0L? Should I change it anyway?
Wilder Penfield

Wilder, you need to change the rocker cover gasket first, then the head gasket (if it’s needed).

Superlift Suspension Review
I installed this with shocks last January on a 2012 JK two-door. I’m running 285/70/17 Treadwright Guarddog tires on stock rims with Spyder wheel spacers. The ride seems a bit stiffer than stock but makes for a great all around rig. BTW: In regards to the guy with the JK gas fill-up problem, there is a TSB and recall on the filler hose. He should take it to his dealer for a free fix.
Tom Crossman

As usual, each month, I’m shouting out a huge THANK YOU to Paul Schupp at Rock Lizard 4x4 in Kingman, Arizona, for his invaluable assistance in answering many of the Jeep Creep questions.

In your Jeep Creep questions, please list your first and last names, your hometown, and your state/province/country, so that we can publish that information here. If you don’t provide this information, we may not be able to publish your question and answer. Don’t forget to be as complete as possible with the description of your Jeep and its problems, too. Send your Jeep questions to, Attn: Jeep Creep.

Previous Jeep Creep Columns
November 2013

October 2013

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