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Techline - February 2015

Posted in How To: Tech Qa on January 2, 2015
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GM Auxiliary Fueling
I have a ’99 Chevy 1-ton Crew Cab longbed pickup. I have been looking for a larger-capacity fuel tank and cannot seem to find one. My truck came with only a 28-gallon-capacity tank.
Pedro Valazquez
Via email

Several companies such as Transfer Flow ( and Titan Fuel Tanks ( offer larger-than-stock replacement fuel tanks for all models of trucks. But I failed to find one for your specific model 4x4. The sort of good news is that Titan Fuel Tanks does offer a 30-gallon auxiliary fuel tank that fits in the spare tire location under the bed. It’s not exactly for your application, but it seems like it could be easily adapted to work. Another option is to go with an in-bed auxiliary fuel tank. These are available in sizes up to and over 100 gallons. Of course, you’ll have to plumb the tank into your fuel system, however some bed-mounted tanks are not legal for use as an auxiliary fuel tank.

Shifting Old Iron
I acquired a classic ’66 Chevy ¾-ton pickup from my uncle recently (amazing how I use the word acquired, yet I still had to pay him for it). It’s a 4x2 and I am very interested in swapping it over into a 4x4. It was originally equipped with the HO72 rear axle, but years ago he swapped that out and installed a Dana 44 frontend and a 14-bolt rearend, both with 4.11 gears. They were taken from an ’89 Suburban. Why he never completed the conversion to a 4x4, I don’t know. Are there any tips that you can give me as to how to go about doing a low-budget build to convert this old truck into a reliable, street-worthy and definitely off-road worthy rig? Currently the truck is equipped with a Chevy 350 with four-bolt mains. It’s backed by an SM465 granny-geared manual transmission. I also want to install an upgraded transmission. This one is pretty worn out and grinds in almost all the gears. Any and all suggestions would be greatly appreciated!
David J. Edwards
Via email

Your truck has all the hard parts of a solid, easy-to-work-on 4x4. However, you should double check to make sure you have the parts you think you have. The ’66 Chevy should have an SM420 four-speed manual transmission. It is also a granny-geared manual truck transmission and similar to the SM465. It features an admirable 7.05:1 First gear that is great for crawling. It’s often swapped into Jeeps because of its compact size, great low gearing, and durability. But the syncros are known to wear with age, causing the transmission to grind whenever you shift it. First and Reverse do not have synchros so they almost always grind, regardless of if it’s freshly rebuilt. An SM465 will typically pop out of gear when it gets old and worn.

The easiest way to tell the difference between the SM465 and SM420 is the size difference and the PTO cover plates. The SM420 has only one PTO cover plate on the drivers side of the case. The SM465 has a PTO plate on both the driver and passenger side. The SM420 case is 10.7-inches long and the SM465 case 12 inches.

Also, the ’89 Suburban that supplied the front axle would have had a GM 10-bolt frontend, not a Dana 44. The two axles are similar and many of the steering and knuckle parts are interchangeable, but it is important to know what you have if you decide to tear into the differential.

The first order of business is to get a transfer case and front driveshaft in your truck. There are several options. If you have the SM420, you could try to locate the Rockwell T-221 transfer case and adapter that originally came in those trucks. Most are divorce-mounted, but some were bolted directly to the SM420. It’s pretty much a bolt-in swap, if you can find one and its related components. They are somewhat rare and replacement parts can be tough to find. In the past, it was a relatively popular transfer case for the deep-mud crowd because it has a dropped rear output, which helps prevent steep driveline angles on trucks with big lifts. There are rebuild and reseal kits still available, but worn gears and broken shafts will have to be replaced with used parts. Other options include using a divorce-mounted NP205 transfer case or use some other transfer case and an aftermarket adapter from companies like Advance Adapters ( or Novak Conversions (

If someone actually did swap in an SM465, you’ll need to have it rebuilt to solve the synchro problem and have a 4x4 mainshaft installed. Just as with the SM420, there are a couple of ways to add a transfer case: You could locate a factory 10-spline NP205 and an adapter, or you might just look for the 4x4 version of an SM465 already bolted to an NP205. Aftermarket adapters are also available to mate your transmission to many different transfer cases. However, I would recommend sticking with the NP205 for your application. If you want to go the easy mail-order route, Novak Conversions offers completely rebuilt SM465 transmissions and Offroad Design ( offers completely rebuilt NP205 transfer cases with adapters.

Now, if you want a more road-worthy transmission, you could look into an NV4500 mated to an NP205. This won’t be an inexpensive combo, but it will get you an Overdrive gear for effortlessly cruising long distances on the highway.

If you decide to go with an automatic, your conversion will be a little more involved but still totally doable.

No matter which route you take, make sure the front and rear axles have the same gear ratio. Once everything is in place, Tom Wood’s Custom Drive Shafts ( can build a new front driveshaft that will fit your truck.

Centered Offset
I have a ’42 MB stretched 8-inches behind the front seats with an SM420, Dana 18 transfer case with a Saturn overdrive, and 3.73:1 gears. I have access to ’86 axles with Detroit lockers and 4.56:1 gears. Can I swap in the ’86 axles behind the Dana 18 (passenger-side offset)? I’m concerned with vibration and reliability issues related to the passenger-side offset to centered rear pumpkin. Any suggestions? Cost is an issue. Bishopdunn
Via forums

Running a centered rear axle with an offset Spicer 18 transfer case can be done, but it usually results in some driveline vibrations and possible driveline binding when the suspension moves and flexes. The 8-inch stretch will help your cause though. The amount of lift your Jeep has will also come into play when making the driveshafts work. To fully eliminate rear driveline vibration, you could consider running a multiple double-cardan CV driveshaft. It is an expensive solution, but it might solve your problems with this setup. Tom Wood’s Custom Drive Shafts ( offers a driveshafts built in this fashion.

Auto Coolerless?
I have a ’04 Jeep Grand Cherokee Larado. It does not seem to have a transmission cooler. I noticed in my Haynes manual they talk about coolers in ’96 up to ’00, then there is no mention of a cooler, and it is not mentioned in the factory owner’s manual. Is it not required after 2000?
Little Stevie
Via forums

All modern-day automatic transmissions require a fluid cooler. The transmission fluid absorbs a lot of the heat associated with the function of the automatic transmission. That heat has to be removed, or the oil and transmission will cook, and they will not live a very long life. This is done in several ways. Sometimes the transmission cooler line is routed into a cooler built into the tank of the radiator. It’s essentially a coiled tube hidden in one of the radiator tanks that is surrounded by the engine coolant. Other applications send the fluid to a typical stand-alone transmission cooler mounted in front of the radiator, and yet, other vehicles use a combination of these two types of coolers. How much cooling is required depends on the vehicle weight, airflow, power, and overall load capacity. Your Jeep was available with both the in-radiator cooler and with a combination of the in-radiator and stand-alone cooler. The Jeeps making more power or those with higher load capacities (trailer tow package, for example) will have more transmission cooling capacity.

If you decide to add more cooling to your transmission, you can keep the stock in-radiator cooler. The auxiliary cooler should be plumbed in after the in-radiator cooler for best performance. You can also bypass the factory in-radiator cooler if you choose to use a stand-alone oil cooler, but never use a T fitting to plumb them in parallel. They should always be mounted in series, with the fluid circulating through the in-radiator cooler first.

Two Jeeps, One Stone
I currently have two Jeeps. Jeep number one is a ‘77 CJ-5 with a 258ci I-4 bored 0.030 over. It has a Clifford intake, 390 Holley carburetor, and a header. The six is mated to an NP435 manual truck transmission and a Dana 300 transfer case. The rear axle is a model 20 with one-piece axles. The frontend is a Dana 30. Both axles are stuffed with 4.11 gears. The Jeep rolls on 33-inch tires cleared with 4-inch lift springs and a 1-inch body lift.

Jeep number two is a ’76 CJ-5 with a stock AMC 304ci V-8 with a two-barrel carburetor. It’s mated to a three-speed transmission and a Dana 20 transfer case. The rear axle is a Dana 44 and the front axle is a Dana 30. I don’t know what gear ratio these axles have. It rolls on 33-inch tires cleared by 4-inch-lift springs.

To make the ’77 into more of a daily driver, should I go with 2-inch springs and a five-speed with the Dana 300? I’d then want to add a Weber carb and switch to 32-inch tires.

Should I put the Holley 390 carb on the 304 in the ’76 and then swap in the NP435?
Jim Search
Via email

Christian Hazel, Four Wheeler editor replies:
The five-speed combo will improve the drivability of the ’77, but if it’s really an NP435 (probably sourced from a Ford) that’s in there, you’ll need a new bellhousing. The T-5 won’t mate to the NP435 bellhousing and the AX15/NV3550 five-speed bellhousing is totally different. Your best bet would be to find an AX15 and bellhousing and use that. It’ll mate right to the Dana 300, assuming your D300 still has the stock 23-spline input shaft. But with any five-speed other than a NV4500, you’ll lose the granny First gear. Honestly, for all the trouble, if all you’re looking to do is add some freeway speed and/or lower your engine rpm, consider cutting your fenders a tad to step up to some 35s. With 35s, you’d be running about 2,885 rpm at 70 mph, which is well within the range of that inline-six. Tire manufacturing is quite exceptional nowadays, and 35s roll and balance just as well as much smaller tires like the 32s you’re considering.

On the ’76 CJ-5, by swapping to the Holley 390, you won’t really see any performance over the factory Motorcraft two-barrel that’s on the 304ci V-8. I’d leave the stock two-barrel on there. They’re good carbs that work very well off-road.

Sometimes the hardest modifications are the ones you don’t make!

Ford Trail Truck
I want to turn my ’94 Ford F-150 into a trail rig and rock crawler. What mods do I need to make it trail ready? I don’t want to blow a bunch of cash on it, I just want something I can go play around in the dirt with. It has a 5.7L V-8, an E4OD, and 31x10.50x15 tires. Other than that, the truck is stock. What systems can I cut out of the truck’s wiring harness?

A stock truck can usually get pretty far down the trail, especially if you aren’t too worried about a few dings and scratches. The mods you should make will depend on the kind of trails you have in mind. First and foremost, make sure you have good solid tow points front and rear for when—not if—you get stuck. Most 4x4s have decent front tow hooks. Make sure your tow strap fits them. Out back, a trailer hitch is an acceptable tow point, but never use a trailer ball as a tow point. Several companies offer a shackle receiver that fits into the factory 2-inch hitch.

Since you’re just getting started, I’d recommend a rear locker. This will help your truck make the traction it needs to get over, up, and through difficult obstacles. A set of sturdy rocker guards are also a great idea for any vehicle that gets into the rocks. Not only will they protect the rocker area of the truck, but they will allow the vehicle to more easily slide over a boulder than crunched body metal. You may also want to replace the shocks if they are old and worn out.

The ’80-’96 4x4 Ford F-150s and Broncos feature Twin-Traction Beam front suspension and solid rear axles with leaf springs. There are many different ways to lift these trucks. They have a lot of aftermarket support from general lift kit companies and the custom go-fast desert crowd. You can decide which direction you want to go based on your driving style and terrain you enjoy most. For typical slow-speed off-roading, a common lift kit will work great.

Many Twin-Traction Beam Ford 4x4s have auto locking hubs. If you haven’t done so already, it’s a good idea to swap these out for Warn ( manual locking hubs. The auto hubs are not very reliable, and the last thing you want is for them to fail a few miles into a trail. Making the swap to manual hubs generally requires the replacement of the wheel bearing adjuster nuts, so keep that in mind when ordering your parts.

Cutting out wiring and other interior systems really won’t benefit the performance of your vehicle much. Your efforts are better spent elsewhere, such as building smooth heavy-duty skidplates.

Where To Write
Have a 4x4 tech question you want answered in Techline, drop an email to or head on over to our forums at All letters become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

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