Q In some of the pictures of trucks, on the axle by the differentials is something that looks like a disc brake. What is that called, and what is the purpose of it?
A What you are looking at is a pinion brake found on many 2½-ton Rockwell axles. The Rockwell axles have very heavy drum brakes from the factory, and by removing them you can lose up to 150 pounds of weight. This also removes issues of mud contamination of the drums and shoes. Adding wheel-end disc brakes isn’t impossible; in fact, companies like Boyce Equipment (800.748.4269, www.boyceequipment.com) offer both pinion and wheel-end disc brake conversions. The pinion brake kits are much cheaper at around $400 while the wheel end brakes are closer to $1,250.
If you run a pinion brake it works similar to a wheel-end brake except that the brakes are applied prior to the axle gear reduction. A pinion brake also works better with some sort of locking differential like a Detroit Locker or spool to disperse the brake to both wheels evenly. A rotor mounted at the pinion will also spin much faster than wheel-mounted brakes, which causes them to heat up more at speed. On the Rockwell the driveline spins 6.72 times for every one tire rotation. This means at 55 mph the rotor will be turning at nearly 370 mph! Driveline brakes are a great off-road–only option, but should not be used on the street.
Q As an off-roader and mountain biker with a full suspension mountain bike, I have always wondered what the significance of the uptravel/downtravel (or sag) is and how it impacts off-road performance. For instance, I see desert race trucks that look like they are set to ride around 80 percent into their travel. It seems like it would be harder to bottom out the suspension and would put unnecessary stress on components. If more uptravel was allowed to absorb the impact from landings, wouldn’t it work better? I realize this would raise the center of gravity and increase the possibility for a rollover, but it also makes sense that if the truck sits at 80 percent into its travel, when it lands a jump the first 80 percent of the travel won’t resist compression enough to slow down the landing, which will be left up to the last 20 percent. This is how it seems to me, and I would love for someone to clear this up for me and correct me if I’m wrong.
A There are a lot of different reasons for how the suspension of a 4x4 is set up. Most stock vehicles run the suspension halfway between full droop and full compression, so that half of the shock shaft is showing. Competitive rockcrawlers often run the suspension with mostly downtravel, so very little of the shock shaft is showing. This keeps their center of gravity low, and since they rarely go extremely fast but need the suspension to droop out into holes and over boulders, it keeps them stable. The go-fast desert type off-road racers often err on the side of 50 percent or more uptravel, so a larger amount of shock shaft will be showing.
This is contrary to what you have seen, so yes, you are wrong, but maybe the trucks you viewed were on display and not ready to race. In fact, the less wheel travel a desert racer has the more uptravel they will factor into the suspension. This is so that if they are bombing across the desert and hit a big ditch or washout, the suspension is able to soak it up quickly.
For a trail rig I would recommend a 50/50 split between up- and downtravel from ride height, but you could adjust this slightly depending on whether you like to run rocks (more downtravel, less shock shaft showing) or run fast (more uptravel, more shock shaft showing).
The Key to Bigger Tires
Q I’m looking for a cheap way to beef up my ’97 F-150 4x4. I want to run 33-inch Mud Countrys but am not sure what to do. What would you recommend to beef it up? It’s currently all stock.
New Haven, CT
A Look into a set of leveling torsion bar keys. A torsion bar key rotates your torsion bars slightly, effectively forcing your A-arms down and raising the truck. Many suspension companies such as Pro Comp (www.procompusa.com), and Revtek (www.revtek.com) offer these and claim a 32- to 33-inch tire will clear. Slight trimming may be required.
Q I have a ’96 Ford Ranger that needs a new transfer case, and I want to swap in a solid axle in the near future but don’t know where to begin. I have been following the “Ranger Rehash” [Mar. ’12 and ongoing] and would like to know what the transfer case is.
A Ali Mansour’s Danger Ranger is running an Atlas transfer case with a 5:1 low range. The stock Borg Warner case was swapped out for the additional low-range gearing of the Atlas early in the build. The original build is available for viewing online at 4wheeloffroad.com.
2 to Go
Q I am 17 and I have an ’01 Chevy ½-ton pickup. I love to wheel and it’s a great truck, but there is a problem. It’s only two-wheel drive. I still do take it off-road, but I can only do mild trails. I know I will never be able to do hard wheeling, but I would like it to be more capable. I have already lifted the truck 2 inches and put slightly larger and better tires on it, but with an open diff I lose traction too easily. Also, having the 4.3L V-6, power is lacking. It seems that a locker and replacing my 3.08 gears with lower gears would be the best option. What would be my best gear ratio and locker? I’m on a tight budget, but I have a job and could afford it with some saving. Also it is a daily driver so I would need the gears to also offer decent mileage.
Vernon Center, NY
A Your truck isn’t a terrible project truck. Yes, it could be better, but as you’re learning this takes time and money. You should seriously consider whether spending money on the 10-bolt is worth it. If you have any inclination to upgrading the truck down the road with parts like a transfer case and solid front axle, then you may want to look into a corporate 14-bolt, and if possible one from a military truck with 4.56 gears and a Detroit Locker already installed. This is, however, opening a can of worms, as you’ll need eight-lug wheels, probably a new driveshaft, and to move the spring perches and buy new U-bolts. For your 10-bolt a set or 4.10 or 4.56 gears and an Eaton posi or Truetrac (www.detroitlocker.com) or Yukon Dura Grip (www.yukongear.com) differential will get you headed down the trail pretty quick, but realize that the parts alone will run you almost $900 and then there is proper install.
There is the possibility that your rear axle is a semifloating 14-bolt, but these are rarer, and although they are stronger they are still not an excellent axle to invest in if you plan on big tires down the road. Unfortunately I have to say it: If you want to go that route, you may be better starting with a 4x4, but if simple dirt roads and easy mud holes are your playground for now, get the gears and posi and go have fun.
Tall, Skinny & Strong
Q I have ’99 Powerstroke and I think I’ve outgrown the flotation mindset in tires. I’d like to find a 36-inch-tall tire in a 91⁄2 to 101⁄2-inch width. Along with a load rating to support the weight of the truck as well towing 7,500-plus pounds. Any suggestions?
A The closest I can find are Interco Tire Q78 Super Swampers (www.intercotire.com), which measure about 351⁄2x91⁄2 inches on a 16-inch rim, but these are only rated at 2,750 pounds, or Load Range C. There are some special Michelin military tires in a 9.00 R16 that measure around 36 inches tall and have a 3,750-pound rating per tire, which would be about perfect. Unfortunately these are nearly impossible to get new and just as hard to find used. If any readers out there know of a good tall skinny mud tire around 36 inches with 91⁄2 to 101⁄2 widths, please email us with the subject “tall skinny & strong” and we’ll pass the info on.
Q I have an ’81 Toyota pickup I purchased with a 2-inch body lift, a Marlin Crawler, and a 22R engine. I live about 25 minutes from the Rubicon. I am dying to run the trail, but money is tight and I only have 31-inch tires and open diffs. You guys have been on the trail a lot, and I was just wondering where I should put the little money I do have. I really want lockers, but I live in the snow and some lockers make driving in the snow impossible. Or should I do a lift?
A Ugh! I would definitely say go with a locker first, but snow is a concern, especially in such a small vehicle with a light rearend. I think your best bang for the buck would be either a selectable rear locker or a winch. The selectable locker, like an ARB Air Locker (www.arbusa.com) would allow you to turn the locker off for snowy roads and would work with the 22R and Marlin dual cases perfectly. The winch would be a different direction, as it would give you an escape route if the open diffs don’t get you through an obstacle. I almost always suggest a rear locker first, but in your case a front locker may be a third choice. You could stuff an Eaton Truetrac (www.detroitlocker.com) up front and then have three-wheel drive from the front end only when shifted into 4x4.
Tires larger than 31s would help also, but that requires the lift and then the snowball effect of gears and so on. If I were you I would choose (A) a friend who has run the trail to go with you and bring a strap if you get stuck; (B) a rear Air Locker; (C) a front winch; or (D) a front Trutrac—in that order.
Finally, contact the folks at Marlin Crawler (888.94-CRAWL, www.marlin crawler.com) and go on the annual Marlin Crawler Round Up.
Nuts, I’m Confused
To Space, and Beyond!
Q I have an ’81 Toyota pickup with 41⁄2 inches of lift and 35s. I am planning on putting a rear axle out of a newer Toyota pickup in it because they are wider. Since my front axle will now be narrower than the rear, are wheel spacers the best way to make the front as wide? I’ve heard people say that wheel spacers wear out wheel bearings faster, then other people say don’t worry about it.
A Are wheels spacers a bad idea? Yes and no. Wheel spacers, like many off-road parts, can require special attention and maintenance. On your truck the best option would be the most expensive: Find or build a front axle that is equal in width to the rear axle. This is not easily done, though the Jeep Wagoneer six-lug Dana 44 may be close depending on what rear axle you are choosing.
A set of wheel spacers is a viable and less expensive alternative. Wheel spacers can add leverage and wear to your bearings, but so can large tires, short-offset wheels, and off-road abuse. For a wheel spacer 3⁄4 to 1 1⁄2 inches thick I wouldn’t be overly concerned.
One thing I would recommend is to vigilantly check and retorque the fasteners on the wheel spacers. Because the wheel spacers bolt to the wheel hub and the wheel then bolts to the spacer lugs, this requires removing the wheel and checking the inner fasteners at the very least after the first 100 miles of driving. It’s not a bad idea to check them every time you abuse the truck off-road, or change the oil, as added insurance. You should also check steering fasteners, brake lines, driveshaft bolts, spring U-bolts, and any other moving parts. All of these can be trouble if not examined now and then for loose or broken parts.
Since your question addresses a concern many off-roaders wonder about I’m picking your letter as our letter of the month. Synergy Suspension is going to supply you with a set of wheel spacers for your Toyota. Synergy offers hub- and lug-centric wheel spacers as well as wheel adapters in case you need to make your wheels match an axle with a different bolt pattern. The spacers are made of billet 6061-T6 aluminum with steel wheel studs. For more information visit www.synergysuspension.com or call 805.242.0397.
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