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Your top 4x4 and off-road tech questions answered here

Posted in How To: Tech Qa on March 24, 2017
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Manual-Shift Quadra-Trac

Is there a replacement for the vacuum actuator on the Jeep BW1339 Quadra-Trac transfer case? My current thought is to make a cable and linkage system.

@rustrunner
Via Instagram @cappaworks

The factory vacuum lines and shift mechanism on the Jeep Borg-Warner 1339 Quadra-Trac transfer case is extremely susceptible to failure from old age. There are a lot of areas of concern. The hoses often crack, connections come apart, switches fail, and the diaphragm in the shift mechanism on the transfer case can rot. Some of the replacement parts are available from BJ’s Off-Road (bjsoffroad.com). The company offers a replacement vacuum transfer case shift switch which mounts in the glovebox, among other parts.

Unfortunately, I don't know of a manual-shift kit for the BW1339, but a few creative garage fabricators have built their own linkage brackets and installed a push-pull cable on the FSJ Quadra-Trac. This home-built modification would eliminate all of the problematic vacuum-shift components on the BW1339.

Wheel Bearing Wonder

Should I expect to change my wheel bearings more frequently if running a wider wheel like a 15x10 with 2 inches of backspacing, or is this acceptable on a solid axle truck?

@aguijimenez
Via Instagram @cappaworks

Wider wheels and more backspacing will inevitably put more strain on wheels bearings, ball joints, the axlehousing, and the steering system. With 2 inches of backspacing, you could also adversely affect steering and handling by increasing the scrub radius. Wider tires and wheels tend to wander more down the road as well, especially over well-worn or uneven rough roads.

The axle you are working with, the tire size you choose, and how you use the vehicle will dictate how long the wheel bearings will last. Solid axles with unit bearings will typically be less tolerant of wide wheels and tires than axles with serviceable wheel bearings. The serviceable wheel bearings found in older axles can be disassembled, repacked, and adjusted more regularly to compensate for the extra stress created by wider wheels and a 2-inch backspacing.

700R4 Swap

I’m putting a TBI Chevy 350 V-8 into an ’88 Toyota. I’m using a standalone harness on the engine with no provisions for the 700R4 four-speed automatic transmission. What is the easiest and cheapest way to operate the transmission? I have a TV cable in place. What else is there?

@weedout1
Via Instagram @cappaworks

The GM 700R4 four-speed automatic transmission is similar to a GM TH350 three-speed automatic transmission, but the 700R4 has an overdrive gear and a few other parts. The throttle valve (TV) cable on the 700R4 transmission controls line pressure, shift points, shift feel, part throttle downshifts, and full-throttle downshifts. If it’s not installed or adjusted properly, it can cause transmission problems.

The TV cable is connected to the throttle lever and a bracket assembly on the transmission valve body. It transfers the movement of the throttle plate to the TV plunger in the valve body, which causes TV pressure and transmission line pressure to increase as throttle is applied. Correct adjustment of the TV cable is based on the TV plunger being fully depressed with the engine at wide-open throttle. Improper TV cable adjustment can cause premature clutch wear and transmission malfunction. Companies such as B&M Racing & Performance (bmracing.com), Lokar (lokar.com), and TCI Automotive (tciauto.com) offer adjustable TV cables for the 700R4 as well as for other automatic transmissions.

The other thing to consider during a 700R4 swap is the torque converter lockup. There are several different methods to address it. We’ve even seen people install a simple toggle switch, although it’s pretty inconvenient on a daily driver. TCI Automotive offers a simple lockup wiring kit for the 700R4 which automatically activates the torque converter clutch in Forth gear under stable engine operation, and disengages the clutch when accelerating or downshifting. The included vacuum switch is fully adjustable so the system can be configured for various vacuum levels. The harness also provides a manual override option that allows complete control over torque converter lock-up if wanted or needed.

B&M Racing & Performance offers a converter lockup controller for the 700R4 (PN 70248), which can be used in your application. The B&M unit provides control of converter lockup through vehicle speed. It includes a dash-mounted controller that can be tuned for a lockup speed between 30 to 90 mph. It features a manual override switch and an LED indicator.

As with all automatic transmission swaps, don’t skimp on the transmission oil cooler. Heat is the number one cause of automatic transmission failure. Consider installing a transmission temperature gauge with the sensor in the transmission oil pan. For longest transmission life you should keep the transmission oil temperature below 175 degrees, although some newer automatic transmissions are designed to run slightly hotter.

Off The Shelf Off-Road

What is the best ’10-current used off-the-shelf 4x4 SUV? I currently drive a ’00 Chevy S10 Blazer and it does pretty well all around, but I'm looking for something bigger that will handle our washboard roads here in Idaho.

@theirishbarber
Via Instagram @cappaworks

Fortunately, in most off-road circles the Chevy S10 Blazer is not considered an off-road beast. There are many more capable and comfortable SUVs to choose from. I think just about any ’10-current Toyota 4Runner is a good buy. There are lots of aftermarket products available to significantly improve off-road performance. To smooth the ride over washboard roads I’d recommend a shock upgrade. Airing the tires down to 12-15 psi will also help smooth the washboard surface.

A ’12-current Jeep Wrangler Unlimited is also a good choice. I prefer the ’12-current model because the Pentastar 3.6L V-6 provides 85 more horsepower than the anemic 3.8L V-6 found in the ’07-’11 model Wrangler and Wrangler Unlimited. You can steer clear of the higher-cost Rubicon trim level because it doesn’t sound like you really need the technical slow-speed capability that it offers. The Sahara models feature lots of creature comforts to keep most people happy.

Unfortunately, if you need a durable fullsize off-road–worthy SUV, you don't have a lot of options. A ’10-current Chevy Z71 Tahoe or Suburban are likely the best choices.

Fullsize Fun

I am looking to build something new. It has to be able to hold four adults comfortably and work well in the rocks. I currently have a Jeep Wrangler JK Unlimited on 37-inch tires. I'm getting rid of it so I would like the new vehicle to go most of the places my current vehicle does. It would need to be street legal with A/C and preferably a V-8. What would you build?

@stevemwright
Via Instagram @cappaworks

Unfortunately, you’re kind of asking for a lot. There are not a lot of 4x4s that can meet all of those needs. About the only other option besides the Jeep Wrangler JK Unlimited is a Ram Power Wagon.

The Ram Power Wagon is the fullsize V-8 pickup version of a Jeep Wrangler Rubicon. It features front and rear selectable locking differentials, a disconnecting sway bar, a real Warn 12,000-pound winch, 33-inch off-road friendly tires, and lots of ground clearance. However, its large size won’t allow it to fit on really tight rocky or treed trails.

The Ford F-150 Raptor is another possibility. Its suspension is better suited in a high-speed desert environment, but it still flexes amazingly well. The Raptor comes with a rear selectable locker, limited-slip front differential, 35-inch tires, and 12-14 inches of bump-sucking wheel travel. The Ford Raptor has slightly less ground clearance than the Power Wagon under the rockers and other body areas, but it’s still very capable of tackling technical rocky trails.

Toothless T-Case

I blew teeth off of the intermediate gear in my Dana 300 transfer case. This is the second time it has happened. Do you see any problems with just replacing the broken gear? I know that when gears wear into each other it’s frowned upon to mix and match them in differentials, but I wasn't sure about transfer cases. I'm lowering the gearing in the axles from 4.10 down to 5.38, which should help reduce stress on the transfer case and driveshafts.

Christopher M Bradley
Via facebook.com/JohnCappa4x4

You are correct. The ring-and-pinion in an axle assembly is designed to be a matched set. When they are made, they are lapped together on a machine to ensure a smooth-running gear pattern and easy setup.

The gears in your Dana 300 are not a matched set. One worn or broken gear can be replaced without causing damage to the other gears or the transfer case. However, the broken teeth of a bad gear can damage the other gears it comes in contact with. You’ll need to carefully inspect the teeth of all the other gears and the bearings inside the transfer case. Chipped or cracked gears and bearings that show damage from gear oil contaminated with metal bits will need to be replaced. Minor surface imperfections in the gear teeth can sometimes be removed with a small sanding disc. Stock Dana 300 gears are getting harder to find. You’ll have to tap into the used market via Craigslist (craigslist.org), eBay (ebay.com), and specialty old Jeep websites and wrecking yards. If you decide to go for deeper gearing in the transfer case than the admirable 2.62:1 stock low range, both JB Conversions (jbconversions.com) and TeraFlex (teraflex.com) offer 4:1 gearsets for the Dana 300. As an added bonus, the JB Conversions gears are significantly more robust than the stock Dana 300 gears.

Regardless of what gears you choose, thoroughly clean the inside of the transfer case. It’s not uncommon for the broken gear teeth to bounce around and find a place to hide, only to later make an appearance and wedge themselves in a bearing or fresh meshing gear assembly. It’s also a good idea to clean the exterior of the transfer case and look for any cracks that could have been caused by the gear failure and resulting gear bind.

Changing the axle gears from a 4.10:1 ratio to a 5.38:1 ratio is a great idea. This modification will help decrease the stress on the driveshafts, transfer case, transmission, and even the engine. Less stress means a longer life for these components.

Grand Swap

I bought a ’99 Jeep Grand Cherokee for one of my daughters to drive. One now drives a Chevy Cruze and the redneck daughter claimed my 2500 Silverado, so I’m stuck with the Jeep. I love it. I did some cosmetic and LED light upgrades. I bought it for the Quadra-Drive with front and rear Vari-Lok differentials. Plus, it has every option for a ’99 Limited. I would prefer a part-time transfer case. Will it fit in the same location? Is it the same physical size? I am sure it won't affect the lockers. I want to put the interior panel indicator in as well with the part-time indicators. Soon I’ll be installing a lift kit, bigger rubber, a roof rack with 360-degree LED lights, a winch bumper, and so on. The Jeep has the 4.7L V-8 and 3.73 axle gears. It seems like a good combo.

Jim Langlois
Brandon, Manitoba Canada

As you may or may not have found, the full-time NV247 Quadra-Trac II transfer case found in most ’99-’04 V-8 Jeep WJ Grand Cherokees can be incredibly handy to have on slippery surfaces like snow and ice. Unfortunately, the NV247 transfer case doesn’t handle bigger tires and wheels all that well. The viscous coupler inside the Quadra-Trac II transfer case is known to wear out. A great replacement for the NV247 is the part-time Jeep NV231. You can’t use just any NV231 though, you need the long input version. JB Conversions (jbconversions.com) offers completely rebuilt heavy-duty NV231 transfer cases that are perfect for this swap. You’ll need to modify the shift linkage slightly, but the factory shifter can be retained. I don’t know of an interior panel that will show the correct part-time transfer case shift pattern. The ’99-’04 WJ Grand Cherokee never came from the factory with a part-time NV231. Although, you could probably have Billet Badges (billetbadges.com) machine a custom aluminum overlay, which could be attached to the factory panel with two-sided tape.

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