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Answers To All Your Jeep Questions

Posted in How To: Tech Qa on February 14, 2019
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Dana 20 Twin-Stick

Is there an OEM replacement lever and linkage assembly for a CJ-7 with the Dana 20 transfer case? I know that there is an aftermarket shifter kit available from Novak Conversions with dual levers. It says the kit is able to do a front dig, but it seems like a bit too much for me. If it will save me some bucks and teach me new things, I’m all for building my own. Do you have any tips or write-ups you recommend for building a twin-stick shifter mechanism?
@joelaw91
Via Instagram @cappaworks

Unfortunately, all Jeep Dana 20 transfer cases came from the factory with a single shifter, so there is no OE twin-stick shifter conversion. As you may have found, the single Dana 20 shifter mechanism can sometimes be difficult to operate and offers only limited traditional shifting functions. The good news is that there are plenty of aftermarket twin-stick shifters available for the Jeep Dana 20. An aftermarket twin-stick shifter conversion can simplify shifting and offer transfer case modes not available with the original single-shifter mechanism, such as two-wheel-drive rear low range and front only. Companies like JB Custom Fabrication (jb-custom-fabrication.myshopify.com) and Novak Conversions (novak-adapt.com) offer twin-stick shifters for the Jeep Dana 20. These kits are simple and easy to bolt on. Some parts from your original shifter mechanism may need to be reused, so read the directions before throwing the old parts away. Most Dana 20 twin-stick shifters run about $120-$150, depending on the model. Of course, you could probably fabricate your own for less, but your time must be worth something, right? Building shifters like this can be time consuming, and it is kind of a learn-as-you-go process. You just have to get in there and get to work. It takes time to figure out the correct shifter length and properly bend the shift levers for clearance around the interior and dash of your Jeep. It’s typically much more cost effective to purchase a twin-stick shifter kit. However, if you insist on building your own, your best bet will be to study the available aftermarket shifters and try to mimic them. You’ll likely want to use at least 1/2-inch-diameter high-quality solid rod, like cold-rolled steel or chromoly. Avoid cheapie metals like rebar, which could bend out of shape when you lay into the shifter.

For fully independent axle operation, you’ll need to disassemble the Dana 20 and either remove the interlock pills or modify the shift rail detents. If you’re already in there, you might as well rebuild your Dana 20 or at the least seal up any leaks. If you do remove the interlock pills or modify the detents, you’ll have to be careful; avoid shifting the transfer case into potentially catastrophic range combinations, such as rear low range with the front in high range. Shifting your transfer case in such a way on all but the slickest surfaces will result in a metal and gear-oil mist emitting from the transfer case, or at the very least a driveshaft flinging out from under your Jeep.

Keep in mind that while the Dana 20 is incredibly robust for its size, it still has weaknesses. Most of the front and rear outputs are 1 1/8-inch, 10-spline; however, some later models are said to have 1 1/8-inch, 26-spline shafts. Although, there isn’t a major strength increase because they are the same diameter. Binding driveline yokes and performing heavy-throttle front digs could snap the front output. The rear output is susceptible to abuse as well, but it can be beefed up with a 1 3/8-inch, 32-spline heavy-duty tailhousing upgrade kit from Advance Adapters (advanceadapters.com).

Independent CJ-2A

How are the axles on the later independent suspension Ford Expedition? I’m thinking of building a tube frame Jeep CJ-2A and I want independent suspension from a factory setup so I can get cheap parts. I’m probably going to use a VW TDI engine or an LS V-8 if I can find an inexpensive one. Any thoughts? What would you advise for the IRS? I don’t think the Explorer IRS is any good.
@xoz.industries
Via Instagram @cappaworks

It sounds like quite the project. I’m sure you are already fully aware that your project will require extensive welding and fabrication experience as well as a ton of knowledge about suspension geometry and handling. The tire size and how you plan to use the Jeep will dictate the parts you should consider. I think the Expedition front axle assembly will be too wide and clumsy for what you are trying to achieve. It will provide all of the disadvantages of a wide axle and suspension assembly with almost none of the advantages. Using the stock IFS and IRS parts all around may not be the best route. This will severely limit the wheel travel, which would sort of be against the whole point of putting in the effort to build a project like this. You might want to take a look at the ’98-’12 Ford Ranger 4x4 front axle assembly and A-arms. Lots of aftermarket support is available for the ’98-’12 Ranger suspension, and the narrower axle assembly would allow for a long-arm long-travel kit without making the Jeep overly wide. Companies such as Camburg (camburg.com), F-O-A (f-o-a.com), and Vegas Dezert Fab (vegasdezertfab.com) offer long-travel 4x4 Ranger A-arm kits that could be adapted to the tube frame of your Jeep.

If you really plan to use it hard off-road, I don’t think any of the factory IRS setups are a viable option. If you don’t mind using aftermarket off-the-shelf parts, maybe consider some VW bug trailing arms, CV axleshafts, and a Currie (currieenterprises.com), Dynatrac (dynatrac.com), or Spidertrax (spidertrax.com) IFS centersection. You should be able to get up to 6x6 (6 inches longer and 6 inches wider than stock) fabricated VW rear trailing arms fairly easily, but you’ll likely need something more common like 3x3 or 3x5 arms to match the front width. Companies such as Dan’s Performance (dansperformanceparts.com), Kar Tek Off-Road (kartek.com), and Moore Parts (mooreparts.com) offer aftermarket fabricated VW rear trailing arms in different configurations. The necessary hardware and other bits are also available from these companies. It should be relatively easy to adapt the VW trailing arms to a tube chassis. If set up properly, you should end up with an incredible amount of ground clearance and wheel travel. You might even consider a similar setup for the front, although the fabricated arms would need to be heavily modified to accept steering knuckles, which probably makes the Ranger A-arms and front axle assembly the best route.

Best GPW Upgrade

What’s the best upgrade I can do on a stock ’45 Ford GPW? I don’t need a coke bottle opener but something priced the same or near it.
@mattmmadrid
Via Instagram @cappaworks

Well, the $4.95 it costs for the installation of a pop bottle opener isn’t a lot of coin to work with. But, if you’re serious and you are interested in only off-road performance, you could pry open the rear differential cover. Be careful though, you’ll want to collect every drop of gear oil in a clean container for reuse. That stuff is expensive and will surely put you way over budget. Next, you’ll need to borrow a welder and burn all of the differential gears together and to the case, essentially creating a low-buck spool. It’s not the best traction device, but it’s cheap. Drawbacks will include binding when cornering, chirping tires, and increased tire wear on the street. The differential cover gasket will no doubt have been damaged during removal, but you should be able to find a replacement gasket or a tube of silicone for $4.95. If you are really interested in climbing ability and don’t care to steer too well, pull off the front differential cover and throw some sparks in there too. A single tube of silicone should be able to seal up both front and rear differential covers once you are done.

Now, if you’re worried that welding the differentials up is a surefire way to convince the local GPW purists to come knocking on your door with torches and pitchforks, we fully understand. You’ll have to look at other options. The good news is that the best way to improve off-road performance is actually free, so you can pocket the $4.95. All you have to do is air down the tires when you hit the dirt. A typical tire gauge will set you back less than $4.95, but if you travel with a group of Jeeps, someone will no doubt have one you can borrow for free (and you could potentially walk off with it, making this a cash-positive transaction). If you’re savvy enough, you might be able to walk off with a tire deflator too. The other option is to just wing it and air the tires down by feel. Simply air down the tires until you see a decent sidewall bulge. Shoving a knee or thumb into the sidewall as you air down will help you match the tire pressure at all four corners. Aired-down tires will improve traction and provide a smoother ride off-road over rough surfaces. The OE tires required 25 psi. Maybe try taking it down to 15-20 psi, or lower if you are in the sand. Experiment with different pressures. Of course, at the end of the trail you’ll need to refill the tires with air before hitting the road. Again, you can potentially depend on someone in your Jeep group to have an air source, just make sure it’s not the same guy you stole the tire gauge from.

If you are interested in spending real money and want to significantly improve the on- and off-road performance of your GPW without destroying the axle assemblies or stealing an air gauge, there is a better way. The factory 6.00x16 NDT tires and 16-inch wheels are about the worst thing you can roll on both on- and off-road. The antiquated tread design and stiff tire carcass can’t even compare to the traction and road performance of a modern radial all-terrain or mud-terrain tire on a slightly wider 15-inch wheel. Slap a set of 30x9.50R15 tires on some 15x7 wheels, and you’ll think you are driving a completely different vehicle. Airing the modern tires down will further increase traction and comfort off-road.

Big Swap

I want to swap out the AX15 five-speed transmission and NP231 transfer case behind a 4.0L for an SM465 mated to an NP241 out of a ’90 fullsize GM truck. Any wisdom to impart on the subject?
@dan.sanford1
Via Instagram @cappaworks

The SM465 is an admirable heavy-duty transmission that has been used in Jeep swaps for decades. By comparison, the 175-pound cast-iron SM465 dwarfs the 85-pound aluminum-case AX15. The 6.55:1 ratio low First gear in the SM465 isn’t quite as low as the 7.05:1 First gear found in the older GM SM420, but the SM465 is far easier to find rebuild parts for. The SM465 is also physically larger than the SM420, which can make it a more complex swap in some applications. Something to keep in mind is that the AX15 is designed to be a true five-speed transmission, meaning all five of the gears are useful on-road, which includes the 3.83:1 ratio First gear and the 0.79:1 ratio overdrive Fifth gear. The SM465 is essentially a three-speed transmission with a 1:1 ratio top gear. You’ll never really find a need for the SM465’s compound low First gear on the street, and the lack of an overdrive can be a real bummer when making long highway drives, especially with the low-revving Jeep 4.0L. On-road drivability is sacrificed, but the 4.0L is probably one of the better engines to put in front of an SM465, thanks to its torquey nature. You’ll likely notice a significant gap when shifting from Second to Third gear, both on- and off-road. It’s not quite the equivalent of shifting your AX15 directly from First gear to Third gear, but it’s close. If your Jeep spends more time on slow, technical trails than it does racing up dunes or on cross-country freeway jaunts, then the SM465 will be a huge upgrade over the AX15 in both strength and functionality. Companies such as Advance Adapters (advanceadapters.com) and Novak Conversions (novak-adapt.com) offer a myriad of adapters to mate the SM465 to all of the popular engines and transfer cases.

Retaining the GM NP241 could be a problem on a lifted short-wheelbase application. Most NP241 transfer cases have an extremely long slip-yoke that will suck up precious rear driveshaft length. This can be countered with the installation of a slip-yoke eliminator kit. JB Conversions (jbconversions.com) offers three different slip-yoke eliminator kits for the GM NP241, including a shorty kit, which reduces the length of the GM NP241 by 9 inches. Which slip-yoke kit you should choose will depend on your budget and rear driveshaft geometry. You may want to sling the assembly into the chassis and take some measurements before deciding.

When making the swap, you’ll have to keep in mind that your new transmission and transfer case are significantly larger than the outgoing parts. You’ll likely have clearance issues on the underbody, crossmember, and elsewhere that will need to be massaged. You’ll also need to modify the driveshafts for fitment.

Sealing 4.0L

Any tips for replacing the rear-main seal on a TJ? Seal number three is about to go in. I can’t keep new seals from leaking.
@kmorgan31
Via Instagram @cappaworks

Given the number of leaky 4.0L rear-main seals we all have seen, you might be fooled into thinking that they were shipped from the factory that way. However, in most cases, the rear-main seal will last at least 40,000-50,000 miles, so it’s not unusual for a high-mileage 4.0L to develop a rear-main oil seal leak. First and foremost, make sure it’s the rear-main seal that is leaking. It’s not uncommon for the 4.0L valve cover to leak oil down the back of the engine, making you think it’s coming from the rear-main seal.

Fixing the 4.0L rear-main seal is a messy task, which involves dropping the oil pan and the rear-main bearing cap. The engine half of the two-piece seal needs to be tapped out of the block around the crank with a hammer and a round-nosed punch. Be careful not to damage the block, bearing, or crank. Slide in the new seal without damaging it and clean the area thoroughly. Clean the rear-main bearing cap and properly install the other half of the new seal in the cap. Dab a little bit of sealant on the corners of the seal on each side of the cap and reinstall the cap and oil pan. For a full story with even more details, check out our 4.0L rear-main seal replacement story on jpmagazine.com here: bit.ly/2MwAMHe.

Wrong Jeep?

I just recently retired and a friend said I should get a Jeep and go trail riding with him. He said any Jeep would do and that there were parts available for all of them. So I went out and bought a ’05 Grand Cherokee. I can’t find anything for it. If I would have purchased a ’04 or earlier, I would have been in business. It has a 5.7L Hemi and a five-speed automatic transmission. What kind of front and rear differentials does it have and where can I get bumpers for both ends?
Name withheld
Via email

Welcome to the Jeep club. Unfortunately, your buddy was a little bit off about there being plenty of aftermarket support for all Jeep models. Some models are significantly more popular with the aftermarket parts manufacturers than others. It is true that you would have far more aftermarket options with the ’99-’04 solid-front-axle WJ Grand Cherokee than you do with the IFS ’05-’10 WK Grand Cherokee, but that doesn’t mean your Jeep is completely left out in the cold. There are several major and niche manufacturers that offer aftermarket parts for your WK Grand.

The front axle is a C200 IFS, also known as the Mercedes 8-inch reverse rotation. There are not a lot of aftermarket modifications you can make to this axle assembly, but Nitro Gear & Axle (nitro-gear.com) offers a 4.10:1 ratio ring-and-pinion gearset to offset the installation of larger tires. The rear axle is a Chrysler 8.25-inch and has a lot more aftermarket support. Nitro Gear & Axle has lower-ratio ring-and-pinion sets, and companies such as ARB (arbusa.com) and Eaton (eaton.com) offer limited-slip and locking differentials to improve traction off-road. ARB also offers a heavy-duty front winch bumper and 2-inch lift systems for both medium and heavy loads. BDS (bds-suspension.com) has a 2-inch suspension lift as well, and for fitting up to 34-inch tires, Superlift (superlift.com) offers a 4-inch lift kit.

Since you are actually taking the WK off-road, the first modification I would recommend is a pair of sliders to protect the rocker areas below the doors. This is the most likely place that you will get body damage when traversing trails with jumbled terrain or when climbing up and down ledges. Companies such as JBA Offroad (jbaoffroad.com), JCR Offroad (jcroffroad.com), and Rocky Road Outfitters (rocky-road.com) offer sliders to protect the rockers of your WK. JBA Offroad also offers front and rear skidplates for your Jeep.

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