Click for Coverage
Exclusive Content
Original Shows, Motorsports and Live Events
Try it free for 14 days
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Techline - Answers to all your 4x4 tech questions

Posted in How To: Tech Qa on July 7, 2016
Share this

Happy Wife Happy Life
How can I convince my wife that all my time and money should go towards four-wheeling?
Kyle Edwards

Easy! Option A is that you take the advice of this vehement bachelor. You tell her you are a grown man and can make your own decisions about time, money, and 4x4s. Then you can give her half of all your stuff, pack whatever is left that hasn’t been mysteriously burned to ash, and move out. Option B is that you accept you aren’t wearing the pants anymore and take a less confrontational route. If done properly, you won’t be camping out on a buddy’s sofa for the next six months and you’ll have a cool 4x4. That’s a win-win for you and your buddy!

The main rule to remember here is that any and all of your whimsical 4x4 dreams, wants and desires will likely be unceremoniously dismissed and flushed down the toilet by your significant other. If you’re like most of us, the money isn’t simply falling off of the trees in your yard, so the limited funds that you do have become earmarked for other presumably more important items such as the mortgage, utilities, food, the kids’ college fund, and so on. However, there are ways you can make 4x4 vehicles and modifications appeal to your seemingly life-sucking better half. There are only two senses that will resonate with the vampire-like individual you are dealing with. The sense of safety and reliability are your keys to the joint bank account. Think about it: no sane significant other would simply let you run off and spend $2,500 on a new set of tires and wheels because you want them. It’s time to accept that your days of being a bachelor are over. You likely won’t be able to convince your family to eat ramen noodles for breakfast, lunch, and dinner for a month like you did when you made such a purchase in your youth. But, if you can convince the purse-string holder that your Jeep would be safer or more reliable with said modification, now you have something to work with. Items such as better brakes, larger radiators, and oil coolers are a no brainer. It’s easy to explain that the improved braking system will keep you from dying and that additional cooling improvements will make your 4x4 last longer, therefore save the family money in the long run. If you hadn’t noticed, the real key here is using the term “family” in your reasoning. Always avoid using “I want” and “I need.” These terms are one-way tickets to Nopeville, and if you use them, you’ll be stuck driving a lame 4x4 for the rest of your life. Over time, you’ll become more skilled at twisting the need of each modification. You’ll eventually have no problem justifying a new suspension lift because the old suspension is worn out, very unstable and too unsafe. How could your significant other be so unreasonable to even consider that you put the entire family in such jeopardy?

Real hardcases will require more aggressive tactics. We all have a buddy who is a police officer. It’s been said that a good patrol officer could write up to three legitimate citations for a brand-new vehicle on a dealer lot. There should be plenty of things “wrong” with your 4x4 that demand immediate attention. Want to dip into the house piggy bank for some new tube fenders or fender flares? Have an officer write you a fix-it ticket for tires that stick out too far and require coverage. Want new tires because yours are worn out? Have him cite you for driving on tires that are worn past the limit. The money-hoarding significant other can’t possibly argue with the sane reasoning of a law enforcement officer. He’s simply trying to keep everyone on the road safe. The policeman then becomes the scapegoat for you to get off blame-free for spending the European vacation fund on your 4x4.

More quality time in the garage and on the trail with your 4x4 is often a hot debate topic under the roof of many households. Again, you’ll have to employ some sneaky tactics. If the 4x4 is your gun, your kids are the ammo in which you need to combat the house-fund manager and resident time burglar. Do whatever it takes to get your kids involved in every aspect of your 4x4. Let them help work on it, let them pretend to drive while you work on it, let them draw on it with Sharpie pens and crayons, take them camping and so on. You want to eventually brainwash your kids into believing everything associated with the 4x4 is fun. This may test your patience to no end in some cases, but always keep your eye on the bigger prize. A little sacrifice and humility on your part will result in great reward. This tactic attacks on three different fronts. First, your significant other will greatly appreciate you bonding with the kids and the time you take them out of her hair. Second, you get to go wheeling and tinker on your 4x4. And third, if the kids enjoy it, you have more justification for spending money on your hobby. How could your spouse possibly consider denying the children all the enjoyment they get from playing with the family 4x4?

Now, if your spouse is overly savvy and you allow her to read this column, you’re out of luck, and I can’t help you. My great advice will have been wasted. Consider option A.

AAM 860 Advice
I need advice from an expert. I have an AAM 860 8.6-inch 10-bolt Chevy rear axle. It has 30-spline ’shafts. Would I be better off with the AAM TracRite EL selectable locker (found in the Hummer H3T rearend) or an Eaton ELocker (PN 19659-010)? Is there a clear winner?
Matt Scott
Via email

In most cases it’s difficult to pick a proper traction-adding device without a lot more information. However, in this case I think it’s pretty much a dead heat. I don’t see one as being stronger or more durable than the other, so either locker should serve you well. They are both electrically actuated with 12Vt power and they engage similarly. Although, there are a few small things you may want to consider. The Eaton ( ELocker will come with all the necessary wiring and a switch you can mount in the dash. You need to build your own harness for the AAM ( TracRite EL. It’s not difficult, you’ll simply have to run the wires from a powered (preferably key-on) switch along the frame and down to the axle. Make sure you keep the wires away from heat sources and moving parts like the exhaust, springs, shocks, and driveshafts. The Eaton ELocker for the AAM 860 requires special bearings. Axles found on vehicles built prior to 1999 generally have small carrier bearing bores (race outside diameter of 2.890 inches), which require bearing LM102949 and race LM102911. Large bearing bore axles (race outside diameter of 3.060 inches) are usually found on vehicle models from ’99 to present. They require bearing LM603049 and race LM603012.

Now, my bigger concern would be with the 10-bolt axle assembly, depending on the rest of the build of course. Your AAM 860 is a C-clip-style axle. The axleshafts are retained in the housing with internal C-clips, rather than with traditional pressed-on bearings and bolt-on retainers. Tires that are 35 inches or bigger, combined with abusive driving while the locker is engaged, can cause failures. If you plan to run large tires and V-8 power, you’ll need to go easy on it regardless of the locker you choose.

Twin-Stick 203
I just got a sweet deal on a rebuilt NP203 transfer case for my ’76 Stepside 4x4. It already has the part-time kit installed. I will put locking hubs on the front axle, but I need a suggestion on the shift linkage. I have been told I need a dual-stick linkage. Any help will be appreciated. Any other ideas while I have it out would be great. I don't want to move this 160-pound transfer case any more than needed.
Roy E. Fisher
Via email

The massive NP203 is a really interesting full-time transfer case. It has the heavy-duty reduction of a gear-driven transfer case and an efficient chain drive to send power to the front axle. With the part-time kit, you have eliminated one of the biggest downfalls of the NP203. The other downfall, as you noted, is the weight. Many NP203s have given up their reduction boxes to be used in doubler kits that mate the gearbox to an NP205. This nearly doubles the crawl ratio of the NP205 for more precise slow-speed off-roading.

The factory NP203 shifter assemblies are typically worn out and can get jammed, making it difficult to shift. The good news is that Offroad Design ( has a simple bolt-on twin-stick kit for the NP203. The twin-stick shifters eliminate the factory shift linkage and replace it with two separate shifters. One lever will shift the transfer case through High-Loc, neutral, and Low-Loc, and the other will control the differential lock, or on transfer cases converted to part-time, the other lever will control 2WD-4WD. The twin-stick shifter is available for GM, Ford, and Dodge-based NP203 transfer cases. They come complete with shifter boots, hold-down rings, and knobs.

16-inch Black Hole
I have been reading Four Wheeler since I was 18. My friend got me hooked on four-wheeling when he let me drive his FSJ. I think it was a ’78. That was before the term SUV was invented and everyone who drove a 4x4 waved to each other. Now I have a ’12 Jeep Wrangler with a 3-inch lift. I thought it would be easy enough to put a set of 35s on it, but it has 16-inch wheels and everyone tells me there is no such thing. I can replace the wheels with 15-inch wheels or I can buy a metric-sized tire and come close. Is there a reason not to put a 35-inch tire on a 16-inch wheel? It would seem like a pretty popular choice since the Jeep JK comes standard with 16-inch wheels? Does it create some kind of black hole that will send me into an alternate universe? If so, will everyone look like Scarlett Johansson?
Mike Kreckie
Via email

Unfortunately, putting a 35-inch flotation-sized tire on a 16-inch wheel will not make everyone look like Scarlett Johansson. Today, only the base Sport model JK comes with 16-inch wheels. All other current JK models come with 17-inch wheels. Industrywide, the 16-inch wheels have kind of been skipped over in favor of 17s. The 16s were originally designed for trucks and SUVs with high load ratings. You will find that many large-diameter 16-inch tires have a load rating of D or E, which makes for a heavy tire and a stiff ride on lighter-duty 4x4s. However, there are load range C 16-inch tires in smaller diameters under 30 inches tall. If you insist on sticking with the 16-inch wheels, take a look at a 315/75R16 tires. These are typically about 35 inches tall and 12 1/2 inches wide, making them very similar to a 35x12.50 flotation-sized tire.

Inverter Denied
I read that the Jeep Wrangler Rubicon came standard with an inverter. I have a ’09 four-door Rubicon, and I can't find it anywhere. Was the article wrong or am I missing something?
Steve Morris
Wonder Lake, IL

Unfortunately, the 115V outlet and inverter option was not available on the Jeep Wrangler until the ’11 model year. However, it was, and still is, standard on the Rubicon and Sahara models from ’11 and up. The good news is that there are many aftermarket inverters available that can be easily added to the interior of your Jeep. Companies like Harbor Freight ( offer several different inverters with output ratings that range from 80 to 6,000 watts.

Hot Tow
I have a ’84 Chevy 1-ton 4x4 dualie with a 454 big-block engine, TH400 automatic transmission and NP208 transfer case. The axles have 4.56:1 ratio gears. I tow a 16-foot lowboy trailer behind it. I went to pick up a 1/2-ton truck. When I started pulling it uphill, I got sick. I had to shift into Second gear and go 35 mph. The temperature gauge hit 260 degrees. What can I do to fix this? Will replacing the automatic with a manual transmission and an NP205 fix this problem?
Trever Nichols
Sparta, NC

Towing puts a lot of stress on the engine and other drivetrain parts. This, in turn, creates heat that needs to be shed from the vehicle via the cooling system. If everything is working properly, your vehicle should not overheat if you are hauling within the specified tow ratings. I sort of wish I had more information about the truck and trailer, such as the tire size and total weight of the towed load, but there are a few things you can check.

Having to downshift on a hill is not unusual, and neither is slowing to 35 mph, especially with an older truck towing a heavy load. However, the engine hitting 260 degrees is a problem. That is much too hot for a Chevy big-block. At this temperature, you are doing damage to the engine. Long before it reaches 260 degrees, you should pull over to let it cool off before continuing on. I recommend pulling over when the engine hits about 220.

Anyway, start by looking over the cooling system. Inspect the fan, fan belt, and fan clutch. Make sure they are all in good working order. You should have a properly fitted fan shroud, and the grille should not be blocked by anything that could impede airflow to the radiator. Inspect the radiator core for mud and bug blockage. You may need to use a hose to flush out the radiator fins from the engine side of the radiator. Oil coolers and the A/C condenser can really hurt the airflow to the radiator if mounted up front. Consider mounting the transmission and other oil coolers elsewhere on the vehicle and attach an electric fan if airflow is limited.

Check the coolant and make sure it’s clean. Radiator tubes clogged with rust and other contaminants will impede water flow. There are heavy-duty replacement radiators available from many different companies that can help shed heat more efficiently than a stock light-duty radiator. You may also want to consider a high-flow water pump and make sure that the thermostat is functioning correctly.

I’m assuming that the engine is properly tuned and that there is nothing wrong with the engine. I’m also assuming that the air/fuel ratio is correct. If the engine is running lean, it could cause an overheating issue. You may want to check the total timing advance as well. If it’s too far advanced, it could cause the engine to overheat more easily.

I don’t think your problem stems from the TH400 automatic transmission and NP208 transfer case. However, if the engine and cooling system are functioning properly, you might be able to decrease the strain on the engine with the installation of a four- or five-speed transmission with tighter gear ratios. This would help keep the engine running in its sweet spot where it makes the most power, without lugging or overrevving and creating excessive heat. This is an expensive and complex solution, so make sure everything else is working perfectly before going this route.

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results