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November 2008 4x4 Truck Tech Questions - Nuts & Bolts

Posted in How To on November 1, 2008
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Submission Information
Confused? E-mail your questions about trucks, 4x4s, and off-roading tech using "Nuts, I'm confused" as the subject and include a picture (if it's applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I'll be checking the forums on our Web site (www.4wheeloffroad.com), and if I see a question that I think more of you might want to have answered, I'll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes.
Write to:
Nuts & Bolts
4-Wheel & Off-Road
6420 Wilshire Blvd.
Los Angeles, CA 90048-5515
fax 323.782.2704.

E-mail to:
nuts@4wheeloffroad.com

Locked Or Lincolned?
Question: I was hoping for a little help. I am debating on whether to put Detroit Lockers in my Scout or weld the gears. The shop owner that just put TBI on my Scout recommended that I get a get a pair of chromoly axleshafts and stronger U joints, and then weld the gears versus putting in Detroits. This is due to the poor handling characteristics of the Detroits on the street.
L.R.
via 4wheeloffroad.com

Answer: Other than cost I don't think welding your differential is a better idea than running a Detroit. A welded differential won't turn as tight as a Detroit and it will increase tire wear. Plus to weld a differential takes some skill, and if it fails you can end up with bits of steel in your gears which isn't good. Also a Detroit Locker isn't unruly if your tires are the same diameter and tire pressure. I've daily driven a lot of Detroit Locked 4x4s and it's weird the first time it unlocks with a bang, but eventually you get used to it and learn to enjoy the reminder. I vote Detroit over welded diff unless it's a low-budget build and the cost of the locker will break the bank.

Ali's Answer
Question: Is there a Web site where I can find out the largest size tire that will fit on a particular vehicle? I've found sites that give the OEM size, but that doesn't help those of us who have an extra set of tires lying around, and they look like they might fit. Specifically, will a set of 31x10.5R15LT tires on 15-inch wheels (from an older Bronco) fit on an '00 Explorer that originally had P255/70R16 tires with 16-inch wheels?
John C.
via nuts@4wheeloffroad.com

Answer: Congratulations, this very issue has the best tire fitment chart of all time by our very own wise guy Ali Mansour. Check it out on page 42. As for your Explorer, the metric tires convert to a 30.5x10R16 so they are just a 1/2 inch smaller in every direction than the tires you want to swap on. Unfortunately, unless you are using wheels from a Bronco II, you will have a different bolt pattern. Early Broncos were 5-on-5 1/2, while Explorers are 5-on-4 1/2.

Recycle, Retread
Question: I'm curious if I could get some contact info on some of the companies that do the small tire recaps. I run a junkyard and am curious if I can become a seller for them and/or provide some tire casings for them. Any info is greatly appreciated.
J.R.
via 4wheeloffroad.com

Answer: Recaps are a great way to get some less expensive off-road tires. What used to be High Tech Retreading is now known as TreadWright (877.439.0759, www.treadwright.com).

Age = Knowledge
Question: Can Rick Pw and Fred Williams both give me an answer on this, because Rick seems like the "Jeep guy," and Fred seems like a "fullsize rig guy." I recently purchased an '81 Chevy pickup from my father-in-law that has a 350 motor and tranny, a Dana 60 front, and a 14-bolt rear. I also own a '69 CJ-5 with a 225 V-6, a Dana 27 front, and a Dana 44 rear that is pretty original except for 31-inch BFGs. I'm not sure if I should do some more mods to the Jeep like a lift, winch, and so on to make it the "ultimate trail mobber," or swap the Chevy big-boy parts into the Jeep and make it a big Ultimate Adventure-worthy rig? Also my buddy gave me his '96 ZJ with a blown tranny for free. Should I do the same thing I was thinking about doing to the CJ to the ZJ? And of course a part of me even wants to build up the Chevy and just sell the ZJ, because there's no way I could part with the CJ. I just don't have the time and room right now for all three.
Big Mike
via 4Wheeloffroad.com

Answer: Pw's off on some wild adventure for his 52nd birthday, so I'll have to give both our answers.

Pw's Answer:
Everyone needs a truck and a Jeep so sell the ZJ, spend the money on a tank of fuel for the fullsize, and use the rest to fill the cooler in the back of the CJ. Use the truck to haul home old Jeep parts; use the CJ to go exploring.

Fred's Answer:
Pull all the 1-ton parts out from under the fullsize and stuff them under the CJ-5. Stretch the wheelbase to deal with the automatic and larger transfer case. Add 38- or larger-inch tires, ram-assist steering, a full cage, and some long-travel suspension. This will of course require a lot more time and money than the Pw version, and this is probably why most of my projects are stuck in the shop while Pw is out on some wild adventure.

Got It Backwards
Question: In mid-engine rigs that you see in rockcrawling, what keeps them going forward when the engine is turned 180 degrees? Do they switch the transfer-case outputs or am I thinking about this way too hard?
M. McKenzie
via 4Wheeloffroad.com

Answer: Most of the time they build custom axles with the centersection turned upside down so it gives them ground clearance and turns in the correct direction. Some use a V-drive that corrects the drive direction. These are made for the marine industry, but have been used in many desert race trucks with rear-mounted engines pointing the opposite direction.

Tow Winch Tech
Question: I need some info on a winch for a '67 K20 Chevy with a 465 four-speed and a 205 transfer case. Is there a PTO hydraulic winch I can mount on my transfer case similar to a tow-truck setup? I have been looking in all the parts catalogs and can only find the one that connects to the power steering.
Bill H.
via 4wheeloffroad.com

Answer: The SM465 four-speed you have, like many older-truck manual transmissions, has a place for a PTO drive. Ramsey (918.438.2760, www.ramsey.com) and MileMarker (800.886.8647, www.mile marker.com) make a full line of hydraulic recovery winches. Most of the dealers can also supply the PTO hydraulic drive pumps, reservoirs, hoses, and control valves.

Budget Bigger
Question: I've got a '96 5.7L 4x4 Chevrolet K1500 pickup and it's hands down the best truck I've ever had. But as we all know, a good truck can always be better. And by better I mean taller, louder, and just plain bigger. Now I'm not someone who can afford to lay down $1,500 or more to achieve this goal. And so I was wondering if there is any way to get the look and the performance of a jacked-up truck without having to break the bank.
John K.
via 4wheeloffroad.com

Answer: You are on a tight budget, but don't fret. If you want your truck louder you need to modify the exhaust. We actually like a subtler exhaust note while wheeling, but going with some Cherry Bomb (www.cherrybomb.com) glasspack mufflers should help increase the rumble without breaking the bank. As for lift, that's going to be expensive with your IFS truck. My advice is to spend your money on a set of 33-inch tires-or 35s if you're willing to trim a bunch of the body to make them fit-and just go wheeling. Save up your money and swap in a solid axle when you have a few grand in the bank.

Nuts, I'm Confused
Spring Versus Sprung
Question: I own a '99 TJ, a typical red TJ on 35s. I have been doing research on custom suspensions in order to build my own. A lot of times I see reference to unsprung weight but I never find more on this. My question is how does unsprung weight affect the vehicle? Handling? On road and off? Can you please explain this to me?
Alison
via 4wheeloffroad.com

Answer: This is a great tech question and something that most off-roaders don't think about until it's too late, thus it wins this month's "Nuts, I'm Confused" tech question prize. Unsprung weight is the weight of any components not supported by the springs of your suspension. So the axles, tires, and wheels are all unsprung weight, whereas the chassis, body, engine, transmission, and transfer case are all sprung weight. Shocks, springs, and suspension links that cross between the sprung and unsprung are divided evenly between the two sides.

In 99 percent of motorsports the goal is to have as little unsprung weight as possible since this is weight that rides along the ground and is affected by the terrain. Lighter unsprung mass allows the tire to better follow the terrain over various imperfections. Lower mass objects are easier to accelerate and change directions. Hit a rock and the unsprung weight must ride up and over it, cross a pot hole and the unsprung weight must drop down in and up out of it. At the same time, in most cases, the sprung weight should be significantly higher than the unsprung weight. This enables the suspension to move rapidly below the chassis without affecting the attitude of the chassis. This means that the driver within the vehicle is isolated from the wheel movement. If the unsprung weight is the same or higher than sprung, the chassis has less ability to isolate itself from the wheel motion. Then the more sprung weight you have the more power you need to move it. It's sort of like that schoolyard game dodge ball-a small guy can move faster but when he gets hit by the ball (unsprung weight) it will knock him on the ground. A big guy is slower but the ball will hardly affect him. Imagine you are tossing an apple in the air and catching it repeatedly. Your arm will not likely move down too much as you catch it. This is because you likely weigh significantly more than a tennis ball. Perform the same toss with a big watermelon and it will likely affect the posture of your shoulders and back. This is because it is much closer to your same weight.

The wild card comes in with rockcrawling. This is the one motorsport where a lot of unsprung weight seems to work because it lowers the center of gravity (CG) and helps plant the tires, but as soon as you include speed like in the rock racers, the additional unsprung weight becomes a detriment. In fact we have seen many rockcrawling competitors fill their front tires with water or lead shot to help lower the CG.

In any case the shocks need to control the movement of the sprung and unsprung weight, and since your question is so good, Edelbrock (310-781-2222, www.edelbrock.com) will be sending you some of its Extreme IAS shocks. These have the patented Ricor IAS technology with a 46mm IAS valve for superior control. This system delivers superior control in demanding conditions by keeping the tires on the ground without sacrificing all of the comfort on the highway. The shock tubes are rolled closed, not welded, for a no-leak seal. A 5/8-inch-diameter Nitro Steel piston rod won't chip or flake, making for excellent off-road durability. Plus these IAS shocks are now zinc-plated and "clearcoated" for long life, and available for lifted trucks with OE mount locations.

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