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Answers To All Your Jeep Questions

Posted in How To: Tech Qa on July 16, 2018
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Anti-Smog FSJ

I have a ’67 Wagoneer with a ’76 AMC 360 V-8 under the hood. I want to strip all of the unnecessary vacuum and smog-related equipment. Is it even worth the trouble?
@electricmike
Via Instagram @cappaworks

I can understand your frustration. Many of the AMC V-8 engines came with a lot more smog equipment than what was originally used under the hood of your ’67 Wagoneer. The numerous smog-related hoses crack and deteriorate with age, which can cause the engine to run poorly and inefficiently. However, the legality of removing the smog equipment will depend on your local laws, so check those before spinning any wrenches.

Now, if you are committed to removing all of the smog gear, you might also want to consider upgrading some parts to help make more power and increase reliability. The first things I would change out are the factory carburetor, air cleaner, and intake manifold. A 600-cfm Holley (holley.com) carburetor (part number 0-1850) will bring a lot of life to your AMC 360 engine. The Edelbrock (edelbrock.com) dual-plane Performer intake manifold (part number 2131) is also a great upgrade. For a simplified and improved ignition upgrade that offers more reliability and power, look into the Performance Distributors (performancedistributors.com) Davis Unified Ignition (DUI). It’s basically a GM HEI distributor that has been modified and tuned to meet the needs of the AMC V-8. With the installation of this new distributor, you’ll be able to remove the entire problematic factory distributor and Motorcraft ignition system.

If you plan to hit the trails with uneven terrain and climbs, you might consider a fuel injection conversion. Howell EFI (howellefi.com) offers a complete GM TBI-based fuel injection kit specifically for the AMC V-8 engines. Some Howell AMC V-8 EFI kits are even smog legal for those residing in states with smog laws.

Clutch Query

The previous owner of my ’95 YJ swapped an NP435 four-speed manual transmission behind the 4.0L inline-six. It’s time for a new clutch and I can’t get a clear answer what clutch will fit. I’ve heard something about a Cherokee clutch but no specifics.
@theliving_log
Via Instagram @cappaworks

Your swapped-in NP435 likely retained the OE 4.0L flywheel, so you should be able to use a factory 4.0L pressure plate. The adaption part will come in the form of the clutch disc. You’ll need a 10.5-inch clutch disc with the proper input diameter and spline count. Your NP435 transmission should have a 1 1/16-inch-diameter 10-spline input shaft. To match this input, you’ll need to use and an Advance Adapters (advanceadapters.com) or Centerforce (centerforce.com) clutch disc (part number 384180). However, before bolting anything up, you should contact Advance Adapters or Centerforce and confirm the components you have to nail down the specifics.

XJ Gearing

What kind of gears would you run in an AX15-equipped Cherokee with 31-inch tires? Also, how much is safe to tow behind an XJ?
@will_yetter
Via Instagram @cappaworks

The 4.0L in the XJ Cherokee is incredibly torquey, no matter if it is backed up with the AX15 or NV3550 manual transmission or the AW4 four-speed automatic transmission. Ideally, you should have 3.73:1 or 4.11:1 ratio gears in the axles, but you could very easily get away with 3.55:1 ratio gears if need be. If you are looking to do a gear swap on the cheap, you could look for some low-mileage axles from a four-cylinder XJ with a manual transmission. These Jeeps will typically have 4.11:1 ratio gears in them. You could simply pull your axle assemblies and install the four-cylinder axle assemblies without having to do a complex and sometimes expensive gear swap.

The tow capacity on most XJ models is around 2,000 pounds. Exceeding 2,000 pounds is not recommended.

Anti-ABS

I want to eliminate the ABS module in my ’10 Jeep Wrangler. Can I make my current master cylinder and brake booster work well without the ABS module? The Jeep is a dedicated trail rig. It’s no longer registered for on-road use.
@chknkatsu
Via Instagram @cappaworks

It’s understandable why you would want to remove the ABS system for off-road use. The antilock braking system can actually be a detriment in some situations where you want the tires to lock up and pile up dirt, mud, or sand to help slow the Jeep down. Unfortunately, there is both good and bad news about removing the ABS system from your Jeep. First, the good news. The factory brake booster and master cylinder will apply the brakes just fine without the ABS module. The bad news is that removing the ABS module will likely cause the ECU to freak out and light up the dash like a Christmas tree. It will also affect how the stability control functions. It may even be bad enough to not let you operate the Jeep. Ultimately, I wouldn’t recommend this modification unless you are completely gutting the Jeep for an entire powertrain swap where you no longer need the factory ECU.

Fuel Finder

My ’82 CJ-7 is very close to being roadworthy. Where do I start to troubleshoot the fuel gauge?
Jason Bent
Via facebook.com/JohnCappa4x4

Does the fuel gauge on any old Jeep ever work? Sadly, the answer is almost always no. But it doesn’t have to be that way. There are only a few areas where a problem could surface, which would cause the fuel gauge of your old Jeep to not function properly. You’ll want to start with the inexpensive stuff first. Check the gauge and sending unit ground wires, ground connections, and any plugs that the ground wires pass through. Clean up any corrosion, replace rotted wires and terminals, and use dialectic grease on the connections. You might even consider running the ground wires directly to the battery to avoid any issues.

Is the gauge still not working right? Make sure all of the power and sender wiring is in good condition. Replace any rotted, cut, smashed, burnt, or poorly repaired wires. If you are still not getting a proper fuel gauge reading, use a multimeter to ensure that the gauge is receiving the proper 12 volts of power with the ignition on. If all of your wiring and connections are on point and you still have a finicky gauge, it’s time to dive into the sending unit. Remove it and make sure that the float still floats. If it has holes in it, the float will sink and the gauge will always read empty. Corrosion on the other parts of the sending unit can also cause the gauge to not work properly.

If you know the output range of the sending unit, you can use a multimeter to test it. If the sending unit checks out okay, the problem is likely in the gauge itself, or you may have a mismatched gauge and sending unit. There are three common sending unit ranges in the aftermarket. If the sending unit sends a signal range that is different than what the gauge is looking for, you won’t get a proper fuel reading. The stock ’72-’86 CJ gauge features a 10-73 ohm impedance range. It reads empty at 73 ohms, 1/2 tank at 23 ohms, and full at 10 ohms. If you don’t know and can’t figure out the ranges of your gauge and sending unit, then you will be better off replacing them as a set to ensure that you get the proper fuel level reading.

M715 Swap

I have a ’69 Kaiser M715. I want to swap the stock drivetrain out for a Chevy 350 V-8, SM465 four-speed manual transmission, and an NP205 transfer case for more reliability. I want to keep my stock axles for now, but will the new NP205 mess up my driveshaft angle to the offset rear Dana 70?
Ben Tipton
Via facebook.com/JohnCappa4x4

Your proposed combo should work fine. The stock Dana 70 rear axle is not as offset as it appears. You’ll likely need to move the engine, transmission, and transfer case over to the passenger side slightly anyway. This should provide the room needed for the exhaust and front accessory group around the steering shaft on the driver side. However, you should pay close attention to the rear driveshaft clearance next to the factory fuel tank. A large-diameter driveshaft could rub the side of the tank when the suspension is articulated or compressed.

Wreck Rehab

I have been rebuilding my Jeep after it lost a battle with a telephone pole. I’m going to install adjustable control arms. Any advice on dialing them in?
Jon Andersen
Via facebook.com/JohnCappa4x4

Installing adjustable control arms on a wrecked Jeep might take some finesse. If the frame was damaged and one frame rail was pushed backward, your frame could be diamond shape. If that’s the case, you’ll have to decide what the best plan of action will be. Adjusting the arms to equal lengths with a diamond frame will cause the axle to look crooked under the Jeep. One tire will appear to be farther forward than the other. If you try to compensate for this by adjusting the arms differently, you could cause the Jeep to handle oddly and suspension components may collide as the suspension cycles, depending on how badly the frame is bent.

If one or more of the original control arms were bent in the wreck, I highly recommend carefully inspecting the suspension brackets on the axle and frame. It’s not uncommon for them to bend, crack, or break off in an accident where the tire and axle make contact and are pushed backward.

Motivational Movement

I by no means want to sell off my Jeep projects, but I am loosing motivation. What would you recommend that I do to get myself psyched and started again?
David W.J. Newman
Via facebook.com/JohnCappa4x4

It’s very easy to lose motivation to work on a Jeep project, especially if you have more than one under the knife at the same time. Different people have different tolerances for what constitutes a project and how many is acceptable. Personally, I’m probably the worst person to ask. I don’t usually feel the need take on multiple project vehicles at once. I quickly feel overwhelmed. There are usually only so many resources available and a limited amount of time to dedicate to Jeep projects. If you take on too many, you’ll likely never finish any of them. So my advice is to stick with one project at a time. Pick the one that is most important to you or the one you are the most excited about. Shelve the rest of them to the back forty so they will not be a distraction. Put all of your efforts into the one project until it’s complete.

Now, if you simply look at your project and you can’t see a light at the end of the tunnel, don’t look at it as one huge project—break it down into many small projects. Some people do this by creating a list of things that need to be done on the project. Once the task is completed, you can cross it off the list. As you progress, the number of tasks that have been completed and crossed off will increase, which offers some encouragement to keep going.

I’m the least motivated when it comes to wiring and plumbing. These two parts of a build really slow me down. Sometimes I’ll procrastinate for weeks to avoid them. It’s not that I can’t do them, quite honestly, I actually enjoy working on wiring and plumbing once I’m in it. I’ve found that the best way for me to tackle the wiring and plumbing is to work on little bits at a time. For example, maybe I’ll only work on it an hour or so and knock out the brake lines on an axle, wire and route long pigtails on the fuel pump, or locate and drill holes in the dash for electrical switches. Any progress, no matter how small, is progress in the right direction. Once I get going, I’ll often be more motivated to work on it longer than an hour. When I poke along like this I’m usually surprised when I realize the Jeep is no longer a project and it’s ready to be driven.

JK Fuel Capacity

First, thank you for your advice on a previous question. I had purchased a ’10 two-door Rubicon and it was a great car except for being underpowered. I asked if it was feasible to swap in a 3.6L Pentastar engine from a wrecked Jeep. You suggested that it was not a cost-effective swap, and recommended that I simply buy a ’12-or-newer Wrangler that already has the Pentastar V-6. So I traded the ’10 in for an identical ’16 and that has worked out very well. I’m really pleased with it for the light wheeling that I do.

Anyway, how can I add fuel capacity to my JK? It’s supposed to have a tank capacity of 18 gallons or so, but I’ve never been able to put that much into the thing. AEV offers a fuel caddy that goes with their fancy rear bumper. Do you know of any other California-legal ways to carry more fuel? Thanks for your help.
Ren Colantoni
Via email

Jeep Wranglers have never really been known for having stellar fuel economy, so adding more fuel capacity is not a new idea. As you mentioned, AEV (aev-conversions.com) offers the Fuel Caddy, which sits behind the spare tire and mounts to the AEV spare tire carrier. The Fuel Caddy carries an additional 10.2 gallons. However, it is not plumbed into the factory fuel system. You have to siphon the fuel from the Fuel Caddy and into your OE fuel tank. It’s not a difficult task, but it’s not particularly convenient and has the potential to be messy if you are not careful.

Titan Fuel Tanks (titanfueltanks.com) offers the Titan Trail Trekker II, which is similar to the AEV Fuel Caddy. It holds 12 gallons and is designed to fit a number of different swingout spare tire carriers.

Another option is to install a GenRight (genright.com) 20-gallon axillary fuel tank. The GenRight aluminum axillary fuel tank fits under the rear floor of all ’07-’18 two-door and four-door Wrangler models. It has several advantageous features. First, it keeps the center of gravity low; 20 gallons of fuel weighs in the neighborhood of 120 pounds. Another advantage is that it is filled through the factory fuel filler cap. Unlike the AEV Fuel Caddy, the GenRight tank is not a transfer tank. It is a completely redundant tank with its own fuel pump. A switch inside the cab lets you choose which tank the engine pulls fuel from. Both the GenRight fuel tank and the factory tank tie back into the OE fuel and emissions equipment. However, the GenRight axillary fuel tank is not emissions legal in California. Unfortunately, the GenRight auxiliary fuel tank sits in the same place as the factory muffler, so exhaust modifications are required for installation.

LongRanger (thelongranger.com.au) is an Australian company that also offers an auxiliary fuel tank for the ’12-’18 two-door Wrangler models. It’s a 42L (11-gallon) tank that is mounted next to the rear driveshaft, on the opposite side of the factory fuel tank. The company also offers a 68L (18-gallon) auxiliary fuel tank for the four-door Wrangler models.

With the stock fuel tank, both the GenRight and LongRanger auxiliary fuel tanks, and a spare tire–mounted fuel tank, you could conceivably carry up to 61 gallons of fuel on a two-door Wrangler and up to 75 gallons on a four-door model. Unfortunately, only the spare tire–mounted tanks are legal for California at the moment.

Hydroboosting

Can I put a hydroboost brake system from a GM or Dodge truck in my ’95 Cherokee?
Nick Camp
Via facebook.com/jpmag

Yes, you can install a hydroboost brake system in your XJ Cherokee. However, you can’t simply bolt one in from a GM or Dodge truck. Fortunately, companies such as Vanco (vancopbs.com) specialize in modifying the hydroboost systems to fit many Jeep applications, including your XJ. The company also offers the pump, high-pressure hoses, master cylinder, proportioning valve, and the brake lines required to make the conversion.

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