NUTS & BOLTS

4 Wheel & Off Road - - NUTS & BOLTS -

DUAL BAT­TER­IES

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.

OVER­DRIVE SQUARE-BODY

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?

JOHN B.

Via [email protected]

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.

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