Click for Coverage
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler
Subscribe to the Free
Newsletter

Techline: Your Top 4x4 And Off-Road Tech Questions Answered Here

Posted in How To: Tech Qa on October 30, 2017
Share this

Odd V-8 Swap
I have an LA-series Mopar 360 with an NP435 transmission and an NV231 transfer case, but I found out the crank is warped and it still needs an intake and a carburetor. I can get a complete Pontiac 350 V-8 for $250 with a two-wheel-drive transmission bolted to it. I should be able to sell the transmission. I'm not sure which engine I'll use in my early Jeep. It's just a matter of if it's cheaper to put the Mopar 360 together or source the transmission for the Pontiac 350. Are there any good 4x4 transmission options for a Pontiac 350 V-8 engine? If I'm reading correctly, it's the same bellhousing bolt pattern as the Jeep Dauntless V-6. I want to keep my swap unique. The Chevy 350 V-8 is so common it's almost boring.
Adam Britton

It might sound fun trying to come up with an oddball original engine and transmission swap combination; however, it's generally much more complicated and expensive to swap an oddball engine into a project than to use a common powerplant like a Chevy 350. It comes down to parts availability. There are plenty of motor mount, header, and adapter options available for the more common engines, while the oddballs may have one option or none. If you don't mind hunting for hard-to-find parts and building your own parts when something isn't available, then the oddball engine swaps can be fun and even rewarding.

Anyway, you have a handful of swappable manual truck-style transmission options that make sense behind the Pontiac 350 V-8. These include the NP435, SM420, SM465, T-19 and Ford T-18. You'll need a bellhousing with the Buick, Olds, Pontiac (BOP) bolt pattern to mate the Pontiac to any one of these transmissions. While the Jeep Dauntless V-6 bellhousing has the correct engine bolt pattern, it will not bolt to any of the desirable aforementioned transmissions. Advance Adapters (advanceadapters.com) offers aftermarket aluminum BOP bellhousings that will bolt up to the NP435, SM420, SM465, T-19 and Ford T-18 manual truck transmissions. Unfortunately, none of the Advance Adapters bellhousings will work with the Pontiac 350. The starter pocket will be on the wrong side. However, Quick Time (holley.com) offers a steel dual starter pocket BOP bellhousing (part number RM-8070) that you should be able to modify slightly to fit the SM420 manual transmission, but it doesn't come cheap. You might also be able to use a factory '60s-'70s BOP bellhousing designed for a Saginaw four-speed to put your Pontiac V-8 in front of an SM420.

If you decide to go with an automatic transmission, the swap is a little bit easier. You can utilize the two-wheel-drive BOP TH350 or TH400 transmission and install a GM 4x4 rear output shaft. Some TH400 transfer case adapters will only need the two-wheel-drive yoke and tail cone removed for installation. Also, many different companies such as Speedway Motors (speedwaymotors.com) and Trans-Dapt (hedman.com) offer an inexpensive adapter plate to mate a Chevy TH350 or TH400 to the BOP V-8 bellhousing bolt pattern. The GM TH350 and TH400 enjoy a plethora of transfer case adapters, although fitting a TH350 or TH400 in the smallish early Jeep will prove to be very difficult, if not impossible, in some cases.

The Mopar 360 mated to the NP435 and NV231 is a pretty long combo. It will be a really tight fit unless you plan to extend the wheelbase of the early Jeep. You'll also have to move the engine, transmission, and transfer case combo fairly far to the passenger side for transfer case and front driveshaft clearance, which will likely cause all sorts of other clearance issues for the exhaust, steering, and other components.

Ultimately, just because you have an engine does not mean it will be a good swap candidate, which is apparent here. You don't have a lot of reasonable cost-effective options with the Pontiac 350, even though the swap may be possible. You would likely be better off with a Buick 350 or even a Buick 455 if you wanted something really original. Either of these engines could be easily mated to a heavy-duty truck four-speed manual transmission with a readily available Advance Adapters bellhousing and clutch parts.

Mud Braking
I have a '12 Jeep Wrangler JK Unlimited on 35-inch tires. I was thinking of upgrading my brakes with slotted and dimpled rotors. Some people say that they don't work well when you get them in mud. Do you think it's worth converting to them or not?M
Ronnie Longoria

Arguments like this have been going on since before the first 4x4 shifted into low range. Some will say that the dimples and slots will help clear the mud from the braking surface, while others will argue that the dimples and slots will trap small rocks and prematurely wear out the brakes. The truth of the matter is that mud is hard on all brakes, regardless of what type of discs, calipers, and pads you have. You should clean the brakes thoroughly after each mud run to avoid any issues. If you hear scraping and grinding, you may need to remove the calipers and pry stones from the brake pads. Having said all that, slotted rotors with performance pads would be a fine idea for your Jeep or any 4x4. You likely spend more time on the street anyway, and this is where the performance brakes will really shine with the larger tires. Consider something like EBC (ebcbrakes.com) Extra Duty or YellowStuff pads. EBC offers several types of slotted and dimpled brake rotors. The EBC High Carbon Blade Slotted BSD rotors are a good option. However, if you are still concerned about the slots and dimples retaining mud and stones, you could opt for the EBC RK-Series non-slotted rotors and still improve brake performance over stock. The EBC brake pads and rotors are also available in complete front and rear kits.

FJ80 Swap or Not
My son picked up a '92 Toyota FJ80 for $800 from a buddy of his. The body is straight and it runs. There is no rust. He's been helping me with my Jeep and now he's got the 4x4 bug too. Would you do an engine and transmission swap or would you stick with the original powerplant?
Joe Garcia

The FJ80 is a great 4x4 and prices have become more reasonable, even for the more rare models with factory front and rear selectable lockers. FJ80s are generally very reliable and slow enough to keep first-time drivers out of trouble. Although, it's usually the slow speed and poor fuel economy that push FJ80 owners to desire a bigger engine. With only $800 invested in a running and driving 4x4, it might be kind of hard to justify performing an engine swap that will cost many times that. The engine is only part of the cost equation. Most people simply forget that there are many other costs to consider, such as motor mounts, computers, wiring, radiator, exhaust, driveshafts, adapters, transmission, and so on.

I've seen some really nice GM V-8 conversions done on FJ80s, but if it were mine I'd drive and enjoy it until the engine or transmission completely let go. After that I'd probably eyeball a Chevy 350 conversion with an overdrive automatic or manual transmission. The newer LS engines are nice, but I think the LS engines and their oiling systems are too finicky when run at odd angles off-road. The iron-block Vortec 350 fuel-injected V-8 engines can be picked up for almost nothing, and there are plenty of power modifications available for them. It can also be argued that the Vortec 350 engines make more torque down low than the LS engines, which is typically better for off-road use in a heavy 4x4.

Ram Axle Advice
I need your advice about what axle I should use to replace my truck's Chrysler 9.25-inch rearend. My current axle is a 5-lug axle with antilock disc brakes. Through my research, I was advised to use the rear axle from an '03 Dodge Ram 2500, which is an AAM 11.5-inch. I was also thinking about using a Dana 60. What axle would require the least amount of fabrication and be the easiest to install, so I could get the selectable locker I need? Thank you for your help!
Jesse Simpson via email

As you have found, locking differential options are somewhat limited for the Chrysler 9.25-inch rear axle found in many Ram 1/2-ton pickups. There are no selectable lockers available for the 9.25-inch. While the on-road driving characteristics of a selectable locker like the ARB (arbusa.com) Air Locker, Auburn Gear (auburngear.com) ECTED Max, and Eaton (eaton.com) ELocker are generally preferred over the handling characteristics of an automatic locker like the Eaton Detroit Locker, it's still difficult to justify making an axle swap like this to simply get the type of locking differential you want. There will be many compromises you would have to make by stepping into a 3/4-ton Ram 2500 rear axle or other junkyard Dana 60 rear axle. All of these 3/4-ton rear axles will have an 8-lug wheel bolt pattern that will not match the 5-on-5.5 lug pattern on your 1/2-ton front axle. Do you plan to carry a 5-lug spare tire and an 8-lug spare tire? You may need to change the axle gear ratio to match your frontend, adding even more cost and complexity to your swap. Also, the 3/4-ton rear brakes will likely overpower your 1/2-ton front brakes. Lastly, do you really need or even want the massive 11.5-inch ring gear and the decreased rear axle ground clearance that the Ram 2500 axle comes with? Of course, all of these problems are surmountable, but it's probably not a cost-effective option. Ultimately, there isn't an easy inexpensive bolt-in junkyard axle swap that will accomplish what you are trying to achieve here. If you are adamant about finding a bolt-in axle for your truck with a selectable locker, you could consider a custom axle assembly from a company like Currie Enterprises (currieenterprises.com) or Dynatrac (dynatrac.com). Either company could build you an ABS-compatible heavy-duty bolt-in Dana 60 with a 5-on-5.5 wheel lug pattern and the selectable locker of your choice. Something like this would likely cost $5,000-$6,500 depending on options. It may sound like a big chunk of change, but when you rebuild, fabricate, and piece together a junkyard axle, the costs add up quickly. It would not be unreasonable for your junkyard axle swap to cost $2,500-$3,500 or more once you get the locker and correct ring-and-pinion ratio installed, the brakes rebuilt, and worn bearings replaced. In the end, it's still a used axle assembly with a mismatched wheel lug pattern. The Currie and Dynatrac axle assemblies will be all new and accept your current wheels and tires.

Your Chrysler 9.25-inch rear axle is easily good for up to 37-inch tires in most cases. The other option is to consider installing an automatic locker like the Eaton Detroit Locker in your existing 9.25-inch axle. The advantages of this option are many. It retains your current axle assembly, 5-on-5.5 wheel lug pattern, ABS brakes, and so on. The Detroit Locker will be far less noticeable on larger and heavier long-wheelbase trucks like your Ram 1500 than it is on a short-wheelbase Jeep. An automatic transmission further decreases the handling quirks caused by a Detroit Locker in the rear axle.

If you are worried or unsure about how your truck will handle with an automatic locker, you can invest in an inexpensive drop-in locker to test it out. The Powertrax (powertrax.com) Lock-Right Locker can be installed into your factory open differential carrier. Installation and removal do not require gear setup, so it's a procedure you can easily do at home. Drop-in–style lockers like the Lock-Right are also less expensive than traditional full-carrier locking differentials. Of course, they are not as strong as a full case replacement locking differential, but they will function and react similarly on- and off-road for about half the price.

Snow Traction Tech I was reading an older Techline (October '16) column this morning. I'm really questioning the answer that was given to a reader about snow performance. Airing the tires down for more traction in snow, are you crazy? The best advice you could have given him is to air up the tires, or invest in the tallest, skinniest tire he can fit. Weight in the bed is also a good idea. You could have suggested one of those bags for water in the bed. A locking rear differential would help, but there's no replacement for weight in the bed for running in the snow. Jeremy Warnick via email

Properly prepping a 4x4 for snow use depends greatly on the type of snow and road conditions you plan to encounter. Traditional wisdom dictates that you want full-pressure, tall, narrow tires in the snow. This is done to provide as much ground clearance as possible. The narrow tires are more likely to dig down through the white stuff into solid earth and provide forward momentum. However, if the snow depth is more than a foot and the surface under the snow is questionable, this combination is a one-way ticket to getting stuck. Off-road enthusiasts who frequent the deep snow have much better success running wider, aired-down tires. This combination provides the same kind of flotation you would want in the sand. Extreme deep off-road snow fanatics run wild wheel widths of 14-18 inches or more and tire pressures down into the single digits.

On the street, ice becomes a concern. A tire at full air pressure is unable to conform to an unevenly packed icy surface. The tire tread is also less likely to open up and expose the sipes that help provide more traction. For these reasons, an aired-down tire is a better choice on the ice, too.

Adding weight to the bed of an empty pickup to improve winter traction is a great idea. Several different companies offer products to help accomplish this, but even a small load of gravel achieves the same results. Off-road, that extra weight is generally not wanted. It simply makes it more difficult to get up and over obstacles.

Installing a rear locker for snow use can be good and bad. Of course it will keep both rear wheels spinning regardless of the traction available, but it's also very likely to cause the truck to slide sideways on icy corners. Some differentiation is desirable on icy roads, so a limited-slip differential is often a better choice. However, if the snow is deep and the surface under the snow is soupy, slick, muddy, or at all unpredictable, the increased traction offered by a locking differential will be a godsend.

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results