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Techline: Your Top 4x4 and Off-Road Tech Questions Answered Here

Posted in How To: Tech Qa on January 26, 2018
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Lift Block Vibes

Will tapered lift blocks cause a driveshaft vibration?

William Peavy

Tapered rear lift blocks are often included with complete lift kits. They are generally used to help eliminate the driveshaft vibrations and binding that can surface when lifting the rear of a 4x4. These lift blocks are positioned so that they taper forward with the thicker parts of the blocks at the rear of the 4x4. In this position, the tapered lift blocks rotate the axlehousing and tilt the pinion upward. This is usually done to keep the driveshaft axle U-joint angle at about 0 degrees and in line with a CV-style driveshaft. However, using tapered rear lift blocks on a 4x4 with a non-CV rear driveshaft could lead to incorrect driveshaft angles and annoying driveshaft vibration. Also, there are different degrees of taper available for lift blocks of varying height. You may need to do some homework under your 4x4 to find out exactly how much taper is needed before purchasing and installing tapered lift blocks.

To find out if your tapered rear lift blocks are causing driveshaft vibration, you should start by identifying if your 4x4 has a CV-style rear driveshaft or not. Next, you’ll want to use an angle finder to see how far off the driveshaft U-joint angles are from optimum. If your 4x4 has a CV-style driveshaft and the U-joint angles are on point, you may have a problem elsewhere in the drivetrain causing the vibration, such as a worn U-joint, bent driveshaft, worn driveshaft slip joint, and so on.

Lighter JK

I’ve been intrigued by two of the concept Jeep Wranglers brought to Moab called Pork Chop and Stitch. Both featured massive weight savings that really livened up the somewhat heavy JK. I’m trying to emulate this on my own JK by removing the factory bumpers and steps, carpet, and back seat, as well as the top and doors in the summer. I even tried to find a reasonably lightweight set of wheels and tires. My next step is to replace the factory front seats. What else do you think that can be done on a reasonable budget for weight savings?

Dustin Gibson

You are definitely on the right track! A lighter 4x4 will generally perform better on- and off-road. Acceleration, braking, and climbing performance will all improve with weight reduction, and so will fuel mileage. Lighter tires and wheels will make a huge difference. Rotating weight is the worst weight to add to a vehicle. Finding a tire and wheel combo that is even 10 pounds lighter per corner will make a noticeable difference in overall performance. Aluminum wheels are usually lighter than their steel counterparts, but some heavy-duty aluminum wheels are porky because of the extra material used for reinforcement.

Radial tires are usually much lighter than bias-ply tires. Look for load range C tires for lightweight 4x4s. The D- and E-rated tires are generally heavier and should be reserved for heavier vehicles that carry heavy loads. The BFGoodrich ( All-Terrain, BFGoodrich Mud-Terrain, General ( Grabber AT2, Goodyear ( MT/R, Goodyear DuraTrac, and Yokohama ( Geolandar M/T G003 are some of the more lightweight off-road–worthy tires available.

There are many other areas in a stock vehicle where weight can be reduced. Window glass is extremely heavy, although switching to a Lexan windshield and windows may not be street legal in some states. If you don’t use the trailer hitch, it can be removed, but make sure you have some other rear tow point. The lead/acid battery in most 4x4s can weight 30-50 pounds. A lithium car battery is expensive, but about half the weight. Removing the stereo head unit, speakers, and associated mounting bits will save a lot of weight if you don’t mind the loss of music entertainment. The spare tire and spare tire carrier can be removed for a huge reduction. Carry a tire plug kit and a small compressor instead of the spare. Of course, the rear seat and seatbelts can be tossed too. Remove all the unnecessary plastic inner fender bits, and if you have a winch, switch to winch rope in place of the steel cable.

4x2 Traction

How do you make a two-wheel drive perform better off-road?

Via Instagram @cappaworks

Making a two-wheel-drive vehicle perform better off-road really isn’t all that much different than making a 4x4 perform better off-road. The three things you’ll want to focus on are ground clearance, suspension travel, and traction.

To improve ground clearance under the rear axle, front suspension, and chassis you need larger aggressive off-road tires. These can be added in several ways. Tire diameter can usually be bumped up one or two sizes without a lift kit. Although, some two-wheel-drive vehicles will require fender and bumper trimming. For even more ground clearance you’ll want to look into a lift kit and larger tires. Not all two-wheel-drive vehicles have lift kits available, but the more popular models do. Also, some 4x4s share their chassis with a 4x2 counterpart. In a few cases, the 4x4 lift kit will also fit the 4x2 version. If possible, find a lift kit that increases the useable suspension wheel travel. In tough situations, you’ll have to use speed and momentum to get through sections where a 4x4 with low gears can walk through. The increased wheel travel will smooth the ride and help you keep better control of your vehicle.

To make the most of your two-wheel drive off-road, you should consider installing a traction-adding device in place of the factory open differential. An automatic or selectable locker would be the best choice. The locking differential will keep both rear tires spinning forward, which will help take you farther up the trail.

Don’t forget to crawl under your 4x2 and look for low-hanging vitals like oil pans, exhaust parts, fluid lines, and so on. Raise anything you can out of harm’s way and install a skidplate of some sort on anything remaining. Rocker guards are also a good idea for vehicles that see rocky terrain, tree stumps, and hills with ledges.


What rear shocks would you recommend for a 1/2-ton pickup? It’s a 4x4 that sees a little off-road and a little towing.

Via Instagram @cappaworks

The factory shocks on most 4x4s give up the ghost before the odometer reaches 30,000 miles, sooner if you drive off-road regularly. Long washboard roads can kill some factory shocks after only a few miles. Fortunately, the aftermarket is flush with many different designs of performance shocks that will bolt directly to your stock shock mounts. The type of shock you choose will depend on how you use the truck and your personal preference regarding ride comfort, performance, and handling. Keep in mind that nearly all performance aftermarket shocks will ride firmer than the stock shocks. They provide more damping, which is needed off-road or when hauling heavy loads.

A high-performance aftermarket twin-tube hydraulic shock will offer more damping and improved durability that is one step up from the stock shocks. The ProComp ( ES3000, Rancho ( RS5000, and Skyjacker ( Hydro 7000, among others, are available for many applications—including lifted vehicles.

If you want a firmer ride and more sporty performance or haul heavy loads regularly, go with a nitrogen gas charged shock like the ProComp ES9000 or Skyjacker Nitro 8000.

If you frequent rough dirt roads at higher speeds, then you might want to steer into some monotube shocks. They offer increased heat dissipation and more fade resistance when jounced for long periods of time. The many monotube shocks available include the Bilstein ( 4600 and 5100, Fox ( 2.0 Adventure Series IFP and 2.0 Performance Series IFP, ProComp Pro Runner, Rancho RS7000, and Skyjacker M95. For even more fade resistance, look for a monotube shock with a remote reservoir. The reservoir increases oil capacity and helps dissipate heat.

A 4x4 that sees a variety of uses and loads may benefit from externally adjustable shocks. The valving on these shocks can be altered without disassembling the shocks. Both twin-tube and monotube adjustable shocks are available to meet your on- and off-road performance needs. Some are easier to adjust than others. For example, the Rancho RS9000 only has one knob with nine settings. Plus, the Rancho Myride wireless remote controller kit gives you the ability to tune the ride of your RS9000-shod 4x4 from inside the vehicle. Other externally adjustable shocks include the aFe Power ( Sway-A-Way external bypass shocks, ARB ( BP-51, Fox Factory Series with the CD or DSC adjuster, ProComp MX-6, and King ( OEM Performance Series shocks with a compression adjuster or bypass tubes.

Kaiser Axle Inquiry

What axles came under the Jeep Kaiser pickups and ambulances of the ’60s? Are these worth saving for parts or restoration? I was just curious because I have to watch one rust daily.

Via Instagram @cappaworks

The Kaiser military Jeep trucks were offered in several variants from 1967 through 1969. These variants included the M715 cargo/troop carrier, M724 cab/chassis, M725 ambulance, and M726 telephone maintenance truck. In total, about 33,000 were offered. The bodies and chassis are similar to the civilian Jeep pickups of the same era, with some noticeable differences. All of these military trucks came with a Dana 70 rear axle and a Dana 60 front axle. However, neither of the axles in these Jeeps are all that desirable, unless you are looking for hard-to-find replacement parts for your M-series truck. The Dana 60 front axle is a closed-knuckle axle with small U-joints and smallish axleshafts, which are much weaker than the traditional 35-spline axleshafts found in modern Dana 60 axles. The closed knuckles don’t turn as sharp as their modern open-knuckle counterparts, the big drum brakes leave a lot to be desired, and the 6-on-7.25 wheel lug pattern is not at all popular with the aftermarket wheel companies. It’s possible to remedy some of the M-series Dana 60 front axle weaknesses with aftermarket parts, but it’s much less work and more cost-effective to simply swap in a modern Dana 60.

The M-series Dana 70 rear axle is just as undesirable, if not more so because of the multitude of rear heavy-duty 3/4- and 1-ton axle options available for a few hundred dollars at nearly any wrecking yard. The M-series Dana 70 rear axle features wacky 23-spline 1.50-inch-diameter axleshafts, huge drum brakes, and the same nearly unusable 6-on-7.25 wheel lug bolt pattern. Of course, the axle can be modified, but there really isn’t an abundance of aftermarket support available for this Dana 70. Let them rust until some M-series Jeep owner finds them when looking for replacement parts.

Factory Ram Options

I’m thinking about ordering a new Ram chassis cab and have questions about a couple of the options. What is the Upfitter Electronic Module (VSIM) that costs $295 and what is the Power Take Off Prep, also for $295? Are they worthwhile options?

Via Instagram @cappaworks

The options you choose for your Ram chassis cab will depend on how you plan to upfit and ultimately use the truck. The Upfitter Electronic Module also called the Vehicle System Interface Module (VSIM) is a Ram-engineered module that allows access to the vehicle systems. For example, if you choose to equip the truck with a crane, you could wire the controls into the factory harness so that the crane only operates when the vehicle is placed in park. Vehicles not ordered with this option from the factory cannot be retrofitted later.

The Power Take Off Prep package offers the capability of mounting a PTO to the side of the transmission and controlling it electronically via the dash and steering wheel controls inside the cab. The PTO capability can be used to power a hydraulic pump, which in turn can be used to operate a hydraulic winch or ram on a tow truck, crane, or other device. One of five PTO options are available for the Ram chassis cab trucks. The PTO has the capability of 60 horsepower and 250 lb-ft of torque. The PTO option is available for both gas and diesel trucks with either left- or right-side PTO accessibility; however, the left side is only available on 4x2 models. A split-shaft PTO is only available with the Cummins turbodiesel engine. It delivers a higher horsepower output, which is ideal for large generators, pumps, compressors, and other equipment.

All three trim levels of Ram chassis cab trucks come standard with an auxiliary switch bank in the lower center console. It features five factory switches and wiring that can be programmed independently to operate lights or other electrical devices.

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