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Answers to All Your Jeep Questions

Posted in How To: Tech Qa on August 9, 2017
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Column Question

I have a ’00 TJ Wrangler with a couple things going on in the steering column that may or may not be related. First off, for several months now my airbag light on the instrument cluster (right under/next to the speedo) is always on, indicating something is wrong I’m guessing. Also, I noticed my horn doesn’t work. I have no idea if that happened at the same time since I rarely use my horn. I did check the two airbag fuses behind the glovebox and they are fine. I didn’t see a specific horn fuse. I would like to get things squared away if you have any thoughts. Also, my turn signal will not turn off after completing the turn, both left and right turns. I’m assuming this is mechanical and that I just need to replace the turn signal stalk, but I wasn’t totally sure on that. Thanks! I’m a longtime subscriber and love the mag!

Brett Siegrist
Denver, CO

The steering columns in modern Jeeps have a lot going on in them. They certainly have far more electricals and switches than the early Jeeps. It’s difficult to tell exactly what happened, although it’s not likely that all of the problems are related. I suspect two different things have occurred. It sounds as though the turn signal shutoff tab simply broke off or wore out. You can purchase the entire turn signal switch assembly from your local Jeep dealer or Mopar (mopar.com). It can be replaced without completely disassembling the steering column.

The airbag and horn issue is likely a little more involved. It’s possible that dirt or gunk has contaminated the electrical connections for the horn and airbag. It’s also possible that these electrical connections inside the steering column simply wore out. Fixing this requires the steering column to be partially disassembled. The steering wheel and airbag have to come off. If you have no experience with modern steering columns and airbags, it’s probably best left to the dealer or a qualified mechanic. Accidentally triggering the airbag during steering column disassembly could injure or kill you.

Best Drivetrain

What is the best transmission and transfer-case combo for swapping a V-8 into a ’47 CJ-2A? I think I'm going with an automatic transmission, but I’m not opposed to a manual transmission if it will fit better. I like how cheap the Chevy 350 is, but my Wrangler is getting a Dodge 360 because I like to be different.

Adam Britton
Via facebook.com/JohnCappa4x4

When you are working with the tight underhood and chassis confines of an early Jeep flatfender, the engine, transmission, and transfer case combination needs to be compact, so options are limited. There are some components that are simply too long for the 81-inch wheelbase and too wide to fit between the factory framerails. Generally, if you don’t plan to extend the wheelbase, a manual transmission will fit much easier than an automatic transmission. Simply put, the manual transmission will provide space for a longer rear driveshaft, allowing for more suspension movement/lift as well as more rear axle options. That’s not so say you can’t fit an automatic transmission behind a V-8 in a stock wheelbase flattie. It is possible, but it will require a lot of planning, mocking up parts, and making changes prior to permanently locating the engine or transmission mounts. You’ll also need a high-pinion rear axle. The rear driveshaft angles on a lifted flatfender with an automatic transmission and a low-pinion rear axle will be unmanageable in most cases.

Choosing the right engine is also important. Odd-ball engines can be great conversation pieces, but they are rarely good for a swap into a flatfender. The engine with the most aftermarket support is usually the best choice. It’s not at all uncommon to have to modify or change an oil pan, relocate part of the accessory group, use a compact gear-reduction starter, or install block-hugger headers when performing an engine swap on a flatfender. Parts like this often don’t exist for odd-ball engines. Keeping this in mind, I'd go with a 5.7L Vortec 5700 V-8. An earlier GM 350 is also a good option when fitted with a TBI or other low-profile fuel injection. As you might have guessed, hood clearance will be at a premium. You may consider a small 3/4-inch body lift to help fit the TBI and air cleaner. Energy Suspension (energysuspension.com) CJ-5 body mounts (PN 2.4101) can be used on a flattie if you supply your own hardware. Ultimately, there have been many people that have fit even big-block GM engines under the hood of a flatfender, but it isn’t easy and it not at all practical. In my opinion, a V-6 is a much better engine choice for a trail flattie than a V-8. Although, the V-8 is great for the dunes.

If you decide to stick with a manual transmission, the T-18 is very compact and can be mated with short adapters. Its shape also affords great front driveshaft clearance. The GM SM420 is another good option, but front driveshaft clearance will be at a premium. The SM420 has a hump on the passenger side that can get in the way. The GM SM465 can be used, but it’s an awfully large transmission overall, which will hang down below the framerails and decrease ground clearance.

Of all the versions of the T-18 that were ever offered, the Ford T-18 is by far the easiest to adapt. The Jeep versions of the T-18 are hit and miss. Some of the FSJ versions of the T-18 have overly long input shafts that are completely unusable in a flatfender Jeep. Both Advance Adapters (advanceadapters.com) and Novak Conversions (novak-adapt.com) offer many adapters for the T-18 as well as for other popular manual and automatic transmissions.

As for a transfer case, there really is only one practical option, unless you plan to swap the rear axle. All flatfender Jeeps came with the Spicer 18 transfer case. It features a rear output which is offset to the passenger side. This requires that the rear axle have a differential which is also offset to the passenger side. Of course, this design has its pros and cons. An important and often unnoticed feature of the Spicer 18 is that the rear output is located below the transmission centerline. This helps reduce rear driveline angles and allows for more ground clearance under the Jeep. The major downfall of the Spicer 18 is also its offset design. It’s very wear-prone, especially if you plan to make long high-speed highway trips. The intermediate shaft and bearings usually wear out before anything else. There were three different intermediate shaft sizes used in the Spicer 18 over the years. The 3/4-inch version is fairly uncommon and typically only found in early military Jeeps. It’s a totally undesirable transfer case unless you are building a period-correct military show Jeep. The 1 1/8-inch version is the most common and perfectly useable. The 1 1/4-inch version of the Spicer 18 is the most desirable. You can also build your own heavy-duty 1 1/4-inch Spicer 18 by installing the internals and outputs of the Spicer 18 onto a Dana 20 case.

30-35 Survive

I have a ’95 YJ with a 4.0L. Is it worth keeping the center axle disconnect (CAD) Dana 30 while running 35-inch tires, or will this just be a waste of my money? It is already geared for the 35s. Other than that it's stock.

@rubicombs
Via Instagram @cappaworks

I get a lot of questions about axle strength. Most of them revolve around wanting to know if a particular tire size and axle combination will hold up or not. This really depends on so many different factors that it’s nearly impossible to answer. The most noteworthy, yet most unpredictable factor is you. Your intended use of the Jeep, the terrain you frequent, and your driving style are incredibly important elements. Could you break the CAD Dana 30 with 35-inch tires? Absolutely! Can you make it live for 20 years by driving sanely? Again, absolutely! You may not realize it, but you are already well on your way to making this combo survive. Retaining the factory open differential decreases the potential for increased stress on the axle housing, gears, axleshafts, and steering U-joints. It will take some pretty abusive driving to break the CAD Dana 30 with an open differential and 35-inch tires. If your Jeep has an automatic transmission, you’ve increased your Dana 30s chances of survival even further. The torque converter of the automatic transmission will absorb and cushion a lot of the harsh shock loading than can cause axleshaft and ring and pinion failures.

The 35-inch tires are the maximum I would consider on any Dana 30 axle assembly with or without a locker. I typically recommend stepping into 1-ton axle assemblies for any Jeep that regularly sees difficult trails on 37-inch or bigger tires.

As with most stock Jeep Wrangler YJ, TJ, and JK front axle assemblies, the CAD Dana 30 will not appreciate being sent into orbit. Too much airtime will result in a bent or broken housing.

A great low-buck swap for the CAD Dana 30, is the high-pinion Dana 30 found in many XJ Cherokees. This swap will get you a more durable and less complex non-CAD housing. The high-pinion gearset is also significantly stronger than the low-pinion gearset when used in a front axle. Of course it’s not a direct bolt-in swap. The coil spring and link mounts would need to be cut off and replaced with properly located leaf spring perches. It’s not a difficult job, but it would require the use of a plasma cutter, oxyacetylene torch, or grinder and a welder capable of laying beads on thick axle tubes. You’ll also need to have at least basic knowledge of proper pinion angle and caster.

Diesel Dream Grinder

I have a Big Ton MJ Comanche and an extra AX15 manual transmission. I'm considering the installation of a more efficient inline-six or the Mercedes OM617 turbodiesel. I’m in the process of considering my axle and transfer case configuration options. My focus is on low cost for a durable daily driver, crawler, and cruiser. If you have any suggestions I'd love to hear them. I’m mostly leaning towards the OM617 diesel swap, but I’d like to know if it would be feasible to switch to Toyota running gear. Will a Wagoneer Dana 44 bolt in if using the stock transfer case?

@doug_lefresh
Via Instagram @cappaworks

Performing an engine swap to increase fuel efficiency may seem like a smart and noble cause. Unfortunately, it’s generally not at all cost effective. In all but the most extreme cases, an engine conversion would never pay for itself in fuel savings. Now, if you already own all the parts needed including the engine, motor mounts, adapters, clutch, exhaust, cooling, fuel system, air filter intake, wiring, and so on, and your time is worth absolutely nothing to you, then maybe you could justify it. However, the reality is that most of us have day jobs and don’t have access to an entire junkyard with all the parts needed to make the swap. The current average cost of gasoline in the U.S. is $2.36 per gallon. Diesel is slightly more at $2.53. Assuming an average of 12,000 driven miles per year, basic numbers crunching provides disappointing results. Increasing fuel economy from 15 mpg from your gas engine to 20 mpg with the new diesel engine would result in a savings of only $370 per year. Even the cheapest engine swaps cost a minimum of about $5,000 to complete once you add in driveshafts, coolant, oil, hoses, and everything else needed to make the Jeep run reliably. A diesel swap is generally more expensive. The Mercedes OM617 alone will set you back anywhere from $1,000-$4,500. Regardless, using these mpg numbers and assuming a cheap $5,000 engine swap, it would take nearly 14 years to recoup the swap cost. And that’s just to break even. We haven’t even considered the cost of engine replacement parts during that timeframe. The Mercedes components are likely much more expensive, further decreasing the savings over the long haul.

Off-Road Ready YJ

What basic changes would you make to a ‘92 Wrangler with a 2.5L to make it more off-road worthy? It already has off-road tires and it has been lifted. Thanks!

@vanmelej
Via Instagram @cappaworks

All Jeep Wrangler models are pretty capable right off the dealer lot. The key is to protect your investment and build on what is there. The 2.5L four-cylinder isn’t exactly a powerhouse, so you don’t want to weigh it down with unnecessary aftermarket wingdings. Take advantage of the fact that your Jeep is lightweight and stick with a lightweight theme. For example, you probably shouldn’t add 3/8-inch-thick steel body armor unless you plan to really rake the Jeep over boulders. Focus on the important areas instead. I highly recommend quality rocker guards on any Jeep that hits the trail. The rocker area is typically the first place that a Jeep gets damaged off-road. The most durable rocker protection attaches to the body mounts and to the body. If you don’t live in an excessively rocky area, consider aluminum rocker protection to save weight.

Every Jeep should have front and rear recovery points. If yours does not, they can be easily added. Bolt-on recovery hooks are available for the front of your YJ. Out back you can install an aftermarket bumper with a receiver hitch or built-in tow points. You might also consider a narrow aftermarket front bumper to improve the approach angle. Look for a front bumper with a built-in winch mount or one that allows a winch plate to be added. That way you can always add a winch later on down the road when funds become available.

Your YJ came with a center axle disconnect (CAD) front axle. This CAD assembly engages and disengages the front axle via vacuum hoses when you shift the transfer case. As I’m sure you can imagine, the system can be problematic and unreliable when it gets older. Consider the installation of a 4x4 Posi-Lok (4x4posi-lok.com). The 4x4 Posi-Lok replaces the factory vacuum lines and electronics with a much more reliable cable-operated shift fork.

Go through the entire Jeep and look for worn bushings, ball-joints, tie rod ends, U-joints, and so on. Replace questionable components and regularly grease anything with a zirk fitting. Staying on top of vehicle maintenance will ensure that your Jeep provides you with many more miles of on- and off-road fun.

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