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October 2008 4x4 Truck Tech Questions and Answers - Nuts & Bolts

Posted in How To on October 1, 2008
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Q My father and I are looking to beef up his '96 1/2-ton Chevy Suburban for mild off-road and some heavy towing. The tired 350 is going for a full rebuild and a turbo, but the questions come in about suspension, most likely 3-inch, but what kits offer good rearend stability for the towing? Also a new axle in the rear is in the plans, but we are not sure what to look for. Something that would swap right in without total modification is preferable. A selectable locker is also going to be in the mix, most likely an ARB Air Locker. Any suggestions would be greatly appreciated.

George R.

A Making a 1/2-ton into a towing machine is an uphill battle, but it doesn't need to be a tremendous headache. If you can find a 91/2-inch semi-floating 14-bolt rear axle out of an '88-'98 light-duty 3/4-ton (these are recognized by their 2500 badge, yet six-lug wheel bolt pattern) it should nearly bolt in and there is an ARB available for it. As for suspension, I agree keeping it around a 2- to 3-inch lift will be best for both wheeling and towing, and I would also invest in some rear air springs such as those made by Firestone Ride Right (800.888.0650, or Air Lift (800.248.0892, to help support the extra weight of the trailer. And finally, look into trailer brakes, a brake controller, and a weight-distributing hitch such as those from Draw-Tite (866.308.9054,

Q I have an '04 F-250 Super Duty four-door with an 8- to 10-inch lift and 44-inch Michelin XL tires, but now I badly need some step rails. Normal step rails won't be any help. I made my own front bumper and have included a photo of the truck.

Dent m.

A If you want something to protect the rocker panels during off-roading, then you are looking for rock sliders. Rock sliders are designed to take abuse off-road, slide over obstacles that want to dent your cab, support the weight of the truck, and depending on the design also offer a step up to get into your truck. Very few companies make serious rock sliders for fullsize trucks, so I suspect you'll need to find a specialty fabrication shop to make you a set or build your own at home.

If you are just looking for a step up into the truck I'd recommend the retractable steps from AMP Research ( and distributed by Bestop (800.845.3567, I used to think these were a gimmick, but they are extremely handy for getting in and out of a tall truck. I keep hoping they will offer a super-rugged off-road version that can be dunked in mud, take some rock abuse, and be shut off when the truck is in four-wheel drive. Hey, AMP, you got your ears on?

Q I am the proud owner of an '02 S-10. It has gotten me everywhere I need to go, except the back nine. The problem is that my truck is two-wheel drive. I really want a 4WD but cannot afford to sell my truck. I am a college student, so I cannot afford to buy a new output shaft and transfer-case adapter. I have devised the plan of divorce-mounting a transfer case. The problem is that I have no experience with doing so. I have never had a truck with one and have never been around one, period. I currently have an NP205 case lying around, but I am considering using a Toyota case instead. My truck has the 4L60E transmission and the 4.3. Now, granted, this swap will not be a permanent solution, but it will be used until I win the lottery or get a better job. Help me!

No Name


A You have a serious quandary. I understand you want to go four-wheeling, but you have a two-wheel-drive truck and little to no money for modification. I think from your letter that you want to put in a divorced-mounted transfer just to get a low-range two-wheel-drive, but if you are also planning to make the truck four-wheel drive, then I must tell you the costs will increase quickly. You currently have one driveshaft from your transmission to your rear axle and you will need two shorter driveshafts if you use the divorced mounted case, plus another driveshaft to the front axle. The front drive axle that you currently do not have and that will cost money to buy and then install. Also the Toyota cases are not divorced-mounted and only a few NP205s are, but those 205s are not that low-geared and also very heavy. My advice, because of your budget, is to save up your money, drive the truck as far as you can with two-wheel drive (bring a tow strap and a buddy with another truck), and then buy a truck with four-wheel drive when you get some money. Changing a truck from two-wheel drive to four-wheel drive is rarely ever cheaper than buying the same truck with a factory four-wheel-drive system.

Q I'm going to be building my own little buggy and I love your magazine as a reference. I read the article by Fred Williams regarding the construction of a buggy frame using tubing, but he referenced plastic or wood as an option (although not suitable for his project). Can you actually use plastic or wood as a frame on a lightweight buggy?

Kevin K.

A Um?! I'm not really sure where you got the idea about using plastic or wood for a chassis from my stories on the Fun Buggy, but you could use plastic or wood to lay out a chassis design that you then build from steel tubing. I have seen a buggy built as a marketing vehicle for Eaton/Detroit Locker that has an aluminum chassis and it is pretty slick. I would imagine that with the advances in plastic technology and carbon fiber you could build a buggy if you had an enormous budget, though I'm not sure either would survive serious rock rash the way steel will, but I'd gladly be proven wrong to see them built. As for wood, I'll tell you what, build a safe reliable wooden rock buggy and I'll send you a license plate.

Q I am having trouble with my 350 transmission. It keeps shooting fluid out of the dipstick. I pressure-washed the tranny and can't find the vent tube ( I thought maybe it was plugged). Am I going in the right direction here with the problem and can you help me locate it?


A If you are going mud bogging, then you very well could have plugged the vent, which is located on the upper driver side of the transmission just as the bellhousing slopes down to the body of the transmission. However you need to suck out whatever is clogging the transmission vent. Don't push it in. Also if you have enough mud in the vent to clog it shut, it might be time to drop the pan and check for dirt and grit.

Q I have a '72 Chevy 3/4-ton 4x4 with a manual transmission. The problem I am having is I recently rebuilt the 350, and added the Victor Jr. 64cc chambered 23-degree heads, which have an angled spark plug and I am using the ACCEL shorty plugs. Can you help me in finding some headers to fit this application? So far I have tried many styles but the constant problem on all of these is clearing the fifth-cylinder spark plug.


A I took your question to Edelbrock and got the following answer:"The Doug Thorley Tri-Ys cleared our angle spark-plug heads, or try the new Edelbrock block hugger (PN 65743)."

Q I want to get rid of my 2-inch suspension lift and 3-inch body lift that came with my '99 Jeep Wrangler. I purchased this as my first vehicle that I drive daily and wheel often. I am really wondering if I should go with a 4- or 6-inch suspension lift, and if I should spend the extra on a long-arm kit?

Daniel K.

A I agree you should ditch the 3-inch body lift as I would go with a 1-inch body lift or none at all. However, I would keep the current 2-inch lift springs. I assume you want to stuff taller tires under your Jeep, but check out this photo of Chris Durham's TJ. Chris runs 40-inch tires with a 1-inch body lift, front spring spacers, a set of long-arm suspension links and a fiberglass high-clearance hood he sells through Chris Durham Motorsports (864.420.1274) along with liberal rear body tub trimming. I think this is a better way to go because it keeps your center of gravity low, making it great for steep climbs, sidehills, and high-speed wheeling. His Jeep is limited in the amount of uptravel it has, so it's no desert race truck. It has Dana 60 axles to hold up to the big 40-inch tires, but the same recipe could be applied to a Jeep running smaller tires and still work well.

Q I recently purchased a set of AAM axles out of an '05 Dodge 1-ton truck. I am going to put them under a '98 Jeep TJ. Are there any aftermarket suppliers that offer gears and lockers for these axles?

Justin F.

A There are gears and lockers available for the front axle. I know ARB offers a selectable locker as it is the same used in the GM 9.25 IFS I installed in the Red Sled Project. I also know that you can get 3.73, 4.11, and 4.56 gears from Randy's Ring & Pinion. Currently no one is offering a rear locker for the rear AAM 11.5 axle, though there is a limited slip from both General Motors and Randy's Ring & Pinion and rumors of a rear locker coming from ARB and a Truetrac coming from Detroit/Eaton in September. Rear axle gear ratios being offered are 3.42, 3.73, 4.11, 4.56, 4.63, 4.88, 5.13, and 5.38.

Q I know a body lift is helpful when it comes to making room for a bigger motor or a different transfer case, transmission, and so on, but when you're out wheeling and flexing on some of these unforgiving trails, doesn't this give you a higher risk of damage due to the increased amount of space between the body and frame itself?


A Yes, you are exactly right. Every body-on-frame vehicle must deal with frame flex, especially when a 4x4 is off-road and the suspension is all twisted up. Though most frames are designed as a rigid structure, few to none are completely flexproof. This is why there are bushings between the body and frame. If you use taller bushings and attach the body with longer bolts you are giving more leverage to both the body and the frame. When you're off road you'll be giving the bolts and body or frame mounting points a real workout, and if they fail you're in for a serious mess when your cab falls off your frame. This is why I recommend using a suspension kit and body trimming to clear taller tires rather than a body lift. I feel you want the suspension to do all the flexing and the body and frame to work as a solid base. If looks are all you're after, then body lifts over 1 inch are fine, but even at highway speeds there are significant forces acting on body and frame so I would never recommend over 3 inches of body lift.

Q I have a '76 Chevy with engine trouble. I thought of rebuilding the 350 that it has in it now and then my attention turned to the '88 plow truck in the yard with a blown transmission. The '88 needs more work than it's worth but has a relatively new 350 General Motors crate engine in it (under 50,000 miles). This engine runs great and is a TBI 350. It sounds like a great swap with improved performance and better fuel economy, which is obviously more important than ever. I wonder why I haven't seen this swap more often. Is there a reason that it's not more common? Is there a wire harness kit to make the swap easier and more dependable than the standard backyard hack-fest.

Justin G.

A In my view the TBI 350 is one of the most dirt-simple fuel-injection systems out there, and swapping one into an earlier Chevy is pretty easy. You can get a great wiring harness from Painless Performance (817.244.6212, with all the connections labeled and the engine should bolt in where your '76 350 is currently. You'll need to add an electric fuel pump or look into one of the mechanical Race Pumps (336.476.9720, for fuel injection. The ECU from the '88 will be needed as well. And though the TBI power isn't the top of the line compared to some crate engines, it's still reliable and strong enough for most trail wheeling.

Q I decided to put a fuel cell in my truck, but heard I should ground the fuel cell. How would I go about doing that? Where do I attach a cable? Or do I even use a cable?

Austin P.

A Yes, I spoke to the crew at JAZ Products (800.525.8133, and they recommended attaching a grounding wire to the steel fuel filler neck of the fuel cell and running it to the chassis. If you have a steel or aluminum tank, you can run a grounding strap from anywhere on the tank to the chassis if it is not mounted to the chassis already, but definitely run the grounding strap on plastic fuel cells.

Q I have an H3 with a leveling kit. I like the gas mileage I get with the 33-inch tires; however, I like the look of larger 35s. Would it be smarter to purchase 35-inch tires and mount them on the factory rims with new gears, or put them on new rims that I would then swap on when I hit the trail? If I get the gears, would my gas mileage stay the same?


A Even if you match the ring-and-pinion gearing to the new tire size it's doubtful you will keep your current fuel mileage. The added weight of the bigger tires, the larger rolling resistance, and the decreased aerodynamics of the larger vehicle are not going to help, so I'd definitely recommend a second set of tires for your Hummer for off-roading. Unfortunately, the lower gearing would help you when off-road by maintaining a factory-spec powerband with the taller tires, but luckily the H3 comes with either 4.10:1 axle ratios stock and many are equipped with a 4:1 low range in the transfer case so hopefully you have the lower gears in yours and I believe you will be fine with the slightly larger 35s off-road.

In this time of astronomical fuel prices it makes sense to watch everything that can help squeeze extra miles from every gallon. Unfortunately most off-road upgrades do not aid mileage. That being said, I like your plan of simple bolt-on additions that can transform your truck before an off-road trip and then be changed back before your next drive to work. Though it may be a little extra work, it is a good way to have your cake and eat it too.

In fact, there are many tricks to upgrading your 4x4 for off-road use that can then be removed after the weekend. For example, a receiver-mounted winch, off-road lights with quick-disconnect wires, and even leaving your heavy tool and recovery bags at home during your daily commute can reduce weight and save fuel. In the perfect arrangement you'd have a set of 35-inch aggressive mud-type tires for your off roading and then some narrow 33s of a milder street tread that you run at higher pressures during the weekly commute. Things like exhausts and intakes can have mixed results depending on the manufacturer, but the theory of a better breathing engine should produce mileage gains. I haven't tested enough of these to tell you which make is proven.

Since saving fuel is an important step every off-roader should consider, I'd like to award you this month's Nuts, I'm Confused letter. To help you get started saving fuel and continue wheeling wild trails, I'd like to award you a new set of Classic style wheels from Mickey Thompson. These highly polished wheels will look great either as your street or trail rims and will get you started on a backup set of wheels and tires for your dual-personality Hummer. The wheels are available in 15x8, 15x10, 16x8, 16x10, 16x12, 16.5x9.75, 16.5x12, 17x9, 18x9, and 20x9 sizes to fit most popular truck and off-road applications.

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