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June 2008 4x4 Truck Tech Questions -Tech Line

Posted in How To: Tech Qa on June 1, 2008 Comment (0)
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June 2008 4x4 Truck Tech Questions -Tech Line

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Techline
Four Wheeler
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Los Angeles, CA 90048.
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More On Chevy Throttle Bodies
Question: I couldn't help but notice that you said that 1995 was the last model year for the 305ci engine in Chevys ("TBI Engine Swap," Feb. '08). Well, that can't be because I own a '96 Chevy with a 305 from the factory. I also don't have any problems with towing because I towed a '52 3/4-ton Dodge Power Wagon on a dovetail trailer with my truck, and there was no bogging down or anything.
Tyler Dotson
via fourwheeler.com

Answer: I am sure you're right, as you actually own a truck with that engine. Yours must have been an early-production '96 as it still has the throttle body. I am no expert on Chevy engines-I just went by what my reference books show, and that was that in 1996, Chevy changed the motor quite a bit with what they called the Vortec 5000 block. This motor had 305 cubic inches with the same bore and stroke numbers, but they called it the 5000 due to the fact that it had a bore and stroke that works out to be 5,012 cc (if you multiply 0.061 by 5,012, you actually get 306 cubic inches). It was also code-named the L30. It had much better cylinder heads and sequential center-port fuel injection in place of the throttle-body setup. The pre-'96 version was considered a low-performance, fuel-mileage engine. In other words, a real dog when it comes to pulling a heavy load.

Now here is a piece of trivia for you. In 1980, because of new and unusual emissions regulations, the only motor offered in Corvettes that were sold in California was a 180hp 305! Go figure.

Anyway, thanks for bringing this up. Now I am sure to get experts writing me to say I am wrong, only half right, or don't have a clue to what I am talking about. Actually, I welcome them. As old as I am, I can still learn a thing or two.

Spare-Tire Adapter For Grand Cherokee
Question: I have a '95 Grand Cherokee Laredo and I was wondering where I could get an adapter to relocate the spare tire to the back of the vehicle like your '96 Grand Cherokee 75,000-mile project truck.
Doyle Daughtry
Monroe, MI

Answer: The first one we used was actually a Mopar accessory that came from a Jeep dealer. It rattled and moved around a lot, and we just were not impressed with it at all.

We finally changed it out for a Tomken (719/395-2526, www.tomken.com) rear bumper and tire carrier. The early production model had a latch that rattled and was hard to use, but the updated version is much better and we are very happy with its operation.

We did make a couple of modifications to it for our particular application later on that will be shown in our "Project Ain't It Grand-er" series in an upcoming issue.

F-250 4x2 To 4x4 Conversion Tips
Question: I have a '92 Ford F-250. It has the 7.5L 460 and 4.10:1 gears in the rear. She's only a 4x2, but I'm considering doing a 4x4 conversion. The truck has sentimental value, so that's why I am considering this. In other words, I will never sell this truck, ever. I figure the best thing to do is just to buy a 4x4 chassis of the same year and have the gears match and what not.

Should I just swap over my cab and box and everything else? Can you provide me with any insight here?
Scott Weeks
Prince George, B.C., Canada

Answer: I have touched on this subject many times before and I am sure it will come up many more times in the future. Over all, both time- and cost-wise, you are a lot better off trading in your 4x2 for a factory-built 4x4.

Now with that said, you're on the right track. However, that may be easier said than done. So let's say you buy a real beater 4x4-you know, one of those advertised as a "great firewood hauler"-because you're not really interested in the condition of the body. Now you find that the drivetrain is completely worn out. Just about every axleshaft, gear, bearing, seal, and U-joint has to be replaced. Maybe that is OK and maybe it's not, depending on just how much money you want to spend. The good thing is that when you're done, your truck may be relatively new drivetrain-wise. Or maybe you buy a rollover with what looks like only body damage. The only way to make sure that the axlehousing or the frame is not bent is by putting it on an alignment rack. You could get lucky, and only maybe a spring is bent-or it could be that everything is trash.

Whatever you do, I would advise against just buying an axle here, a transfer case someplace else, springs from another source, and so on unless you have lots of time and patience and are willing to have your truck apart for a considerable amount of time while you run down the little parts to make it all work. It's important to remember that even within a model series, there can be mechanical changes that may or may not allow a direct bolt-on, so be ready to cope with that.

I think that the most important thing to remember when taking on a project like this is to have all the parts and pieces on hand before you start, be able to recruit enough people to help you make the body transfer, and above all, don't set a deadline as to when it has to be finished.

Wants To Build A Plug-In Unimog
Question: I am considering an electric-powered off-road vehicle. I would like to convert a Unimog 411 hardtop to electric power using a DC system. My concern is creating the effect of compression braking. Any experiences or ideas?
Eric Pringle
Cerritos, CA

Answer: I don't think that the world is quite ready for an electric-driven off-highway vehicle due to the many complications involved. However, with that being said, an electric off-highway vehicle would be very cool.

First off, the amount of battery capacity to handle the loads would have to be quite high. Keep in mind that most battery-powered cars available are small and lightweight, and have a very limited mileage range. With current technology, the battery design for something used off the highway ... well, it just isn't going to happen overnight. What could be worse than having your battery go dead miles off the highway without a plug-in site? Plus, electric DC motors usually have a limit of around 2,200 rpm. So without going through a transmission with an overdrive unit, overall speed would have to be limited to electric-motor rpm.

There are a couple of ways to tackle this project, and both would require a motor/generator along with a battery pack. The simplest would be to have a motor/generator somehow incorporated within the driveline of the vehicle, with the vehicle's original motor also providing power. The electric motor would have to be mounted just behind the gas/diesel engine and in front of the transmission. That way, it would be like one of the current hybrid cars. Naturally, there would have to be some kind of specialized control unit that would decide when to use the electric motor. All this would add weight and a very complicated system to the vehicle.

The second and most ideal method, while perhaps not practical and overall speed-limiting, would be to ditch the transfer case as well as the driveshafts and somehow mount a motor at each wheel, right next to the portal section of the axle. This way, you would be able to control the amount of power to each wheel as necessary. Just imagine being able to apply total power to a wheel with traction and just let the others roll along. For this to operate properly, it would take a highly sophisticated computer feedback system to be able to distinguish between wheel slippage, such as when going around a corner and/or when extra traction is needed, plus the necessary program to change the field load to each motor when using it as a braking system.

So what it comes down to is, you had better have a team of electrical and mechanical engineers as well as mega-dollars to tackle a project like this.

Scout II Axle-Swap Sources
Question: In response to "Scout Dana Swap for CJ-7," (Mar. '08), here are some links and info that may prove helpful.

Several companies offer reverse shackle kits that allow for full-width Scout, GM, fullsize Jeep, and Dodge axles to be installed under later CJs. A few are Poison Spyder Customs (www.spydercustoms.com), Expert Off Road (www.expertoffroad.com), and Mountain Off Road Enterprises (www.mountainoffroad.com). Also, according to FAQs on the Binder Bulletin site (www.binderbulletin.org), '80 Scout II front axles have 2 degrees of caster built into them. Caster correction bushings can also be purchased that allow for up to 1.5 degrees in caster for earlier Scout front axles from Super Scout Specialists (www.superscoutspecialists.com). Hope this info helps!
Brett Henderson
Conifer, CO

Answer: You're right-these companies do have full-width axle kits for CJs, and I am well aware of their existence and perhaps should have included them. I didn't for a couple of reasons. One, they are shackle reversal systems. Not that I'm against that, as I am a real supporter of rear shackle solid front mounts. They take a lot of stress off the spring and spring mounts, and do improve ride quality. The serious rockcrawlers don't like them because they allow the axle to move rearward when it's up against a solid obstacle. By contrast, with the shackle in front, it forces the axle forward and into an obstacle for better traction.

Here is where I see the problem, and I did mention it in my initial answer. The steering box has to be moved forward to accommodate the longer pitman arm when using the Scout axle. This makes for more fabrication work to make a correct steering-box mount. I think that it would be impossible to move the box forward using the kit from Expert Off Road due to the design of their kit that utilizes a new front bumper (which, by the way, I think is really cool).

Shackle reversal kits also move the axle about 1.5 inches forward, which makes it mandatory to move the steering box even further forward. Not that someone with some good fabrication skills couldn't do this, but then again, if he had the skills in the first place, he wouldn't need to buy the kit, would he?

Shackle reversals also require a driveshaft with about twice as much travel as a standard shaft. So when you factor in the cost of the new long-travel slip-yoke front driveshaft and an outboard spring mount kit ($400 to $500), new steering knuckles for the Scout axle, and all the miscellaneous parts to make it happen, the Scout axle doesn't look all that inviting.

And that, again, brings up the subject of caster angle. My reference book shows the '80 Scout at 1 degree caster and all the earlier years at 0. Even if the '80 model year had 2 degrees (and how many '80 Scout axles are you going to be able to locate?), and even if you used some offset caster bushings that offer 1.5 degrees of increase, that is not nearly enough caster angle for good handling. (I like to see 5-7 degrees.) Not to mention the fact that the pinion angle will totally suck. The only real way to correct the pinion angle/caster angle is to cut the weld holding the steering knuckles to the axletube, rotate them, and reweld.

Anyway, thanks for your insight on this and I really do appreciate readers setting me straight on issues and offering alternate solutions to problems.

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