NUTS & BOLTS
Q I’m in the process of modifying my 2009 Toyota Tacoma into a mild overlanding rig. I don’t plan on doing any extreme trails, but I’m really into hiking and plan on using the Tacoma as a base camp for some multiday hiking trips in the backcountry. A 12-volt fridge is among the plans for my rig, but I’m really concerned about killing the battery on the truck. There will be times when I might be away from the truck for a couple of days, and it would be awesome to come back to cold drinks, not to mention fresh food. Should I try and add a dual battery system to the truck? How long can a couple of batteries run a fridge and still have enough juice to start the truck?
JOHN M. Via [email protected]
A A 12-volt fridge-freezer is easily among the top five all-time best purchases we’ve ever made. Not having to worry about ice or soggy food is life changing, whether you’re out for a day or a week. For all their benefits, however, the one drawback over a regular cooler is that they draw power in order to work. If you’re off-roading it’s not a big deal, as the engine is running all the time and the battery stays charged. But a running fridge in a vehicle that sits for a day or more can suck a battery dry.
The actual amp draw of the fridge is going to vary according to several factors, including ambient temperature, the location of the fridge (shade or sunlight, inside a vehicle or outside), ventilation, and how often its opened. That said, it’s safe to assume it will draw 1 to 1.5 amps whenever it’s plugged in. Our experience has been that in order to keep up with an average fridge, you want to run a vehicle equipped with a good battery for a minimum of 30-45 minutes a day, preferably driving it around (not just idling). An alternator only puts out a fraction of its output potential at idle, hence why we recommend driving the vehicle.
For people who plan on running the vehicle that their fridge is plugged into at least once a day, nothing in the way of modifications is really needed. But obviously, running the vehicle once a day is not going to work for your extended hiking trips. Many fridges have built-in voltage monitors and shut themselves off before the battery is drained to the point of not being able to start the vehicle, but that doesn’t help if you’re looking forward to a cold beverage after a two-day hike, not to mention relying on a function that could strand you.
A dual battery system is a very viable solution in your case, especially one in which the fridge battery is isolated from the engine battery. A good deep-cycle battery with a large reserve capacity should be capable of running a shaded fridge for a couple of days and you would still have a fresh engine battery to crank the truck. Most dual battery management systems allow you to cross-connect or isolate the batteries on demand while also allowing the vehicle’s alternator to charge both when the engine is running.
Another thing to consider is a solar panel. Even a small 25-watt solar panel should be able to keep up with a fridge and help keep the battery topped off on bright, sunny days. We recently ran across a very comprehensive battery management system with built-in solar functionality from Redarc (redarc.com.au). The company offers several different controllers that can manage two or even three batteries.
While you would certainly want to thoroughly test your setup before setting off into the backcountry, a dual-battery system with an isolated fridge battery and a solar panel should offer plenty of power as well as peace of mind when parking your vehicle for several days with the fridge running. As a safety, throw one of those lithium-ion jump packs in the glovebox and make sure it’s charged up before you head out.
SOLVED: GRAND CHEROKEE BIND
Q I recently bought a 2007 Jeep Grand Cherokee with a Hemi and the Quadra-Drive II system. It’s in great shape and only has 72,000 miles on it. The morning after I bought it, I was pulling out of my driveway and turning into the street when I heard this binding/groaning noise coming from the front end, almost like the Jeep was in four-wheel drive when it wasn’t. This noise continued every time I turned for maybe 10 minutes and then suddenly went away. It does this just about every time it’s cold, but the noise goes away once the Jeep warms up. Everything looks to be in great shape on the front end, with nothing visually wrong. No lights or codes. The only thing I can figure is maybe something is wrong with the transfer case. Any ideas?
SANDY M. Via [email protected]
A We recently had the same issue on a 2005 Grand Cherokee. According to several forum threads, it is somewhat common to this generation of Grand Cherokee. The forum jockeys blame everything from the wrong oil in the differentials to bad bushings, while it appears that a few shops and dealerships have misdiagnosed the issue as the transfer case and have handed customers a repair bill for a couple grand while not fixing the problem. With such low miles it is highly doubtful that the transfer case is the culprit. Here’s hoping your fix is as easy as ours—under $80. Read on.
The Quadra-Drive II is a pretty neat but rather complicated full-time 4WD system. The NV245J transfer case has full-time Hi as well as 4-Hi and 4-Lo. In full-time mode there is a clutch pack in the transfer case that sends varying amounts of power to the front and rear axles depending on traction conditions. This is the same transfer case that’s in the Quadra-Trac II systems in the earlier WJ Grand Cherokees, but what makes the Quadra-Drive II system different is the electronically controlled front and rear limited-slip differentials (ELSDs). Both the clutch in the transfer case and the ELSDs are hooked to the traction control system, which can regulate the amount of slip between the front and rear outputs while also varying the amount of slip allowed between the tires on each axle. According to factory literature, the ELSDs can be entirely unlocked just like an open differential and can add varying amounts
of resistance to the point that they can even lock up, making them act like a locking differential. That’s a lot of moving parts and electronic gadgetry, but as long as everything works, the system is pretty slick.
The ELSDs are controlled by a solenoid that regulates the amount of slip allowed between the tires. This solenoid can start sticking, which causes the limited-slip to tighten up when it shouldn’t. The traction control system doesn’t know that the solenoid is stuck, as there is no feedback to the electronic nannies, so it often doesn’t throw any codes or lights. For whatever reason, once the oil in the differential starts warming up, the solenoid frees up and starts working as it should. For equally unknown reasons, these sticky solenoids usually happen on the front axle. It could be simply because the front tires spend more time rotating at different speeds, or it could be that the front sticking is simply more noticeable.
Let the vehicle sit overnight. Then with the vehicle in Park, jack up the front end so that both tires are off the ground. The front tires should spin opposite each other with very little resistance, just like an open differential. If they don’t, lower the vehicle and drive it around until the binding noise goes away. Jack the vehicle up again and see if the front tires spin freely. If they do, you have a sticky solenoid. If they don’t, disconnect the pigtail on top of the front differential housing and spin the tires again. If they free up, then there’s likely a wiring or electronic issue.
Fortunately a genuine Mopar ELSD solenoid can be had for about $60. The service manual calls for removing the front differential to change it, but that’s not necessary. Unbolting the front mount allows the differential to rotate enough to remove the inspection cover on the front axle without tearing apart the whole front end. The solenoid itself is a simple R&R. Don’t forget to add friction modifier to the gear oil when you fill it back up, and be sure to use 75W-140 synthetic.
Q I have a 1977 Chevy K20 with an SM465 and an NP205 transfer case. I would like to replace this setup with a Tremec five- or six-speed transmission to gain an Overdrive ratio. Could this be done using an older divorce-mounted transfer case? I know the rear driveshaft would be much shorter than it is now (not a bad thing). The front driveshaft would be substantially longer and might require a support bearing similar to the one used on the current rear driveshaft. I’d also have to fab up crossmembers to support everything. Has anyone ever done a conversion like this? Any guidance is appreciated.
LARRY A. Via [email protected]
A Tremec transmissions have a solid, welldeserved reputation in the car world. They’re strong, lightweight, and versatile. Their short-shifting patterns are awesome, but they aren’t well suited for trucks for several reasons. First, their gear ratios are less than ideal for trucks, with the lowest available First gear ration of 2.97:1. Compare that to the SM465 6.55:1 First and 3.58:1 Second. This high gear ratio doesn’t do anything to get a heavy truck with tall tires moving, nor does it do well with low-range crawling. Second, trucks are heavy and they are often used to haul and tow heavy loads for a long time. The Tremec transmissions weren’t designed for that. Third, we’re not aware of any way to attach a transfer case to a fiveor six-speed Tremec tranny other than Rockland Standard Gear (rsgear.com), a company that at one time was advertising adapters for later-model transfer cases like an NP231 and NP241. However, this was some time ago and there is no information on the company’s website now, making us suspect the project was abandoned—not surprising because once again, the ratios are pretty far off for a truck application.
All that said, you could do exactly as you propose and run a T-56 with a divorced transfer case. You would be on your own when it comes to fabricating mounts for the case, and since Tremecs are pretty long (up to 27 inches), you might run into driveline issues if your truck is lifted. You would have to find a divorced NP205 because you won’t be able to use your own, and those don’t
exactly grow on trees in the passenger drop you need. The intermediate shaft also means an extra driveshaft to maintain.
If we were in your shoes and wanting a transmission with Overdrive that didn’t shift like a dump truck, we’d take a hard look at an NV4500. Used in GM and Dodge trucks in the 1990s to the early 2000s, they have the proper gearing (including Overdrive) and torque capacities for your 3 ⁄ -ton 4 truck, and they have a substantially shorter throw. They can’t be shifted fast, but we’d consider them halfway between a traditional truck tranny and a car tranny. They can also be easily adapted to your existing NP205 with help from Advance Adapters (advanceadapters.com) or Offroad Design (offroaddesign.com). Oddly enough, finding a donor tranny from a Dodge is better than a Chevy in terms of adapting, and the Dodge version is much more common. For all but maybe drag racing, the NV4500 is really the better and most likely less expensive way to get Overdrive.
ROLLCAGE VS. SPORT BAR
Q What’s the difference between a rollcage and a sport bar? Which do I want for my weekend wheeler that’s also a daily driver?
A There’s no hard and fast “official” definition, which is partially why the terms are confusing. Generally speaking a rollcage is a weld-together or sometimes bolt-in piece that was designed as one unit, while a sport bar is an add-on piece to an existing roll bar. But people also use the term sport bar (including Jeep) to refer to a factory roll bar with a single B-pillar hoop and spreaders that go front, or back, or sometimes both. To further muddy the waters, sport bar is also a marketing term intended to deflect liability, as roll bar implies rollover protection. Many years ago we purchased a weld-in cage kit from a very well-known brand that had a sticker noting that the “light bar” was not intended for rollover protection. In our highly litigious society, roll bar and
rollcage carry a lot of liability with them for the manufacturer, which is why many avoid using the terms.
No matter the term, there are lots of options on the market, particularly for Jeep vehicles. Some of them are very good and some are pretty sketchy, so it’s up to each wheeler to do the research and make a decision based on needs, usage, and budget.
But whether you go with an add-on piece or a full cage, the same principles apply. In the case of Jeeps, we like to operate on the assumption that any addition to the factory stuff is better than nothing, especially pre-TJ. We generally prefer weld-in cages over bolt-in systems, but that’s not to say there aren’t a couple of manufacturers making pretty good bolt-in kits, including Rockhard 4x4
(rockhard4x4.com) and Rusty’s Off-Road (rustysoffroad.com). The integrity of weld-in kits is also largely dependent on the skills of the person doing the welding and the equipment used, so unless you or a buddy of yours is a qualified welder it’s best to have any roll bar welding done by a professional. That’s why a bolt-in cage might make more sense (and be safer) for do-it-yourselfers.
As for what to look for, 1.75x0.120wall DOM tubing is suitable for most noncompetitive rollcages. Crossbars and triangulation is important, so the more of that you see, the better. Bolting a cage to a floor is better than no cage at all, but whenever possible tie the rollcage directly to the frame, or at least to other body armor, to help spread the loads encountered during a roll.
So why would you want a cage for your weekend wheeler/daily driver? Accidents can happen just as easily with a weekend wheeler as they can with a hardcore trail rig. Just try and go with the best cage you can afford, regardless of what it might be called.