Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

October 2010 Nuts & Bolts

Posted in How To on October 1, 2010
Share this

Floating or locking?
Q I'm 15 and I own a '78 Ford F-150 that was my grandfather's. I'm considering a 4-inch lift and 35s. It's nothing extreme, but I want it to be capable. I would like to convert the 9-inch differential to a full-floater, but I don't know whether to wait on that and get a locker first, or should I get a full-floater conversion kit and then just weld the spider gears inside of the carrier? I've been debating this for the last four months and would really like to hear someone's opinion on it.
Zach R.
Olivehurst, CA

A Before you spend money on a full-floater kit, let's compare it to a locking rear differential. A full-floating axle is good because it takes the stress off your axleshaft and puts the entire weight-carrying load on a spindle that is bolted or welded to your axlehousing. This is smart if you are carrying heavy loads, plus if you break an axleshaft you can remove the internal shaft parts and the wheel and hub can stay in place. These are all good points. However, by choosing this you have decided to then weld up your rear differential instead of buying a locker.

A selectable locker like an ARB Air Locker or automatic Detroit Locker will allow some differentiation of tire speed when going around a corner on the street (but not when the ARB is engaged); this is not true of a welded or spool rear diff. This differentiation of tire speeds is much better for tire life and axle parts. You don't want to wear out those new 35s right away, do you? If it were me, I'd keep the semifloating rear axle setup and instead get a quality locker (the Detroit is usually less expensive). If you can afford it, get a 35-spline unit and upgrade to some quality 11/2-inch 35-spline semifloating rear axleshafts I think you'll have a very strong rear axle capable of living up to the 35 long enough to pass the truck on to your grandson someday.

Which J?
Q Hi. I am 13 years old and currently in possession of an old WWII Willys Jeep. I am planning to restore it or at least make it roadworthy. I was wondering if you could tell what it is by the photos and where I can find parts for it in Ontario, Canada.
Tylor F.
Ontario, Canada

A I showed your photos to the resident Willys flatfender Jeep expert here (Editor Péwé), and after drooling over the photos he determined that it is a '50s/'60s Willys-Overland Kaiser-Frazer CJ-3B. The larger speedometer signifies it as a later model, probably in the mid '60s. However, Kaiser-Frazer, the company that owned Jeep at that time, started discontinuing the Willys name in the mid '60s, so yours may be early '60s. A great early Jeep information site is The CJ3B Page,

I don't know of a Jeep parts house in Ontario, but there are many good restoration/modification companies out there such as Willys America (, Willys Overland (, and Walck's 4 Wheel Drive (

Dynatrac Dilemma
Q I have a '79 Jeep CJ-7 and cannot decide what rear axle to put into it. I'm 29. I bought my Jeep when I was 16 and have been modifying it ever since. It was my daily driver for many years; however, I still drive it as much as I can. My old Renegade is far from stock now. It has a Cummins 4BT engine, an NV4500 transmission, a Dana 300 transfer case with a TeraLow 4:1 kit, a Grand Wagoneer front Dana 44 that has been narrowed to widetrack CJ width, an ARB Air Locker, 4.10 gears, and crossover steering.

My dilemma is the rear axle. I have an AMC 20 with 4.10 gears, a Powertrax locker, custom six-lug Moser one-piece axleshafts, and Grand Wagoneer backing plates and drum brakes. The axle is, you could say, U-shaped, not straight. The axle seals leak a bit, the diff-cover is smashed up, I recently broke a shock mount, and to make matters worse, last month my left rear wheel was not tightened securely and my brake drum came crashing to the ground and damaged my brakes. The brakes work, but will not pass inspection. I have previously vowed not to put any more big money into the rear axle (yes, "big money" includes the cost of new brake drums and pads.) I built up this axle 10 years ago (same time I built the front 44). Soon after, I decided that I would just put a Dynatrac Dana 60 in my Jeep when the AMC fails me.

The CJ is turning 37-inch rubber, and I want to start wheeling longer distances. I live in Pennsylvania and would like to get out to Moab in the next year or two. So, I'm now married five years and have a 20-month-old son and another child on the way. What rear axle would you recommend for this particular setup? My desire is a Dynatrac ProRock60, but I would have to be very intentional about saving up for it, and even that would take longer than my Jeep can wait for a new rear axle. I've considered having an axle from a fullsize truck cut down to fit my CJ, but I really like the high-pinion idea (since my Jeep is sprung-over).

There seem to be limited resources out there for my particular need. What have others done? What would you recommend? What could I do for, say, half the price of a ProRock and still be happy?
Marc D.
Manheim, PA

A I'm of the frame of mind that you get what you pay for, and I definitely feel that way about Dynatrac's axles. The company's sales guys, engineers, welders, and gear techs all strive to build the best parts possible. For example, I saw one of the Dynatrac welders take the time to start and finish the weld on the bottom of the axletube, out of view, making the housing look that much better, and this on a strong double-pass weld that holds the knuckles on the tube. It's that type of pride in one's work that makes you feel good buying Dynatrac products, products that are mostly made in America. Now, I'm not saying these axles are cheap.

Many Jeep guys stuff GM 14-bolt axles and Dana 60s from 1-ton '80s era pickups in their Jeeps with great results. These low-pinion axles do have driveline issues, but with the many wheelbase stretching options available this can be gotten around.

There really isn't an easy high-pinion rear axle option for your Jeep. Other than a custom-built Dana 60, the only other reasonable rear would be custom 9-inch housing like a Spidertrax or Currie with one of the true Hi-9 dropout carriers. These are very strong and could be built to your specifications.

I think the biggest catch is your wanting to narrow the housings. This will require special axleshafts, retubing the housing if done properly, and a complete rebuild of the axle inside and out. Before you go this route, I'd get a price from Dynatrac. I think you might find it in the same ballpark, and you would be getting completely new parts.

Early Explorer in Rubber
Q I am a 17-year-old avid reader that has just recently bought an SUV, a '03 Ford Explorer. It runs great, but over this winter I slid on ice into a curb and took a chunk out of my wheel, so I have been running on a spare. Where can I buy wheels and tires for an affordable price? I need wheels that can take me off-road and yet get me to work, to school, and possibly on trips down Interstate 5 here in Oregon. What would be fitting for my vehicle?
Chance E.
Medford, OR

A There are plenty of places to buy tires and wheels. I know there is a 4Wheel Parts in your area that can sell you different wheel-and-tire packages, as well as National Tire & Wheel and the Tire Rack. All these advertisers are in our magazine and have websites you can order directly from. I used to live in Oregon and I'd recommend a tire that is good in the rain (since the rainy season in Oregon is about half the year). You'll also want something that isn't too loud for highway driving and yet still has some aggressive tread for exploring the hills around Medford, not to mention the snow you'll encounter going up to Mt. Hood for snowboarding. I'd recommend an all-terrain tire, like the BFGoodrich A-T, Nitto Terra Grappler, General Grabber A/T, Dick Cepek Radial F-C, or one of the many Michelin truck tires. In fact, I had a chance to test the new Michelin LTX M/S 2 in both wet and dry terrain and it worked very well, though it's not as aggressive as some of the other tires mentioned.

Heirloom or Headache?
Q I inherited this great '93 FZJ80 Land Cruiser that my father special-ordered new from Japan back in the day. He actually had it made to his specs and waited for it to arrive in the U.S. I hope to preserve and enjoy it before passing it on to my little boy, who's 3 years old.

Here's the problem. The truck is cosmetically holding up great, but with 203,000 miles it is mechanically wearing out quickly. I used to say that it leaks oil like the Exxon Valdez, but a more recent environmental catastrophe sadly requires me to say that it leaks oil like the BP Gulf rig. I go through more than a quart every thousand miles, and it's getting worse. It uses oil and also leaks it from the pan.

The question for you guys is how do I go about dealing with a tired, old engine? I can have a local Toyota expert remove and rebuild my engine, but it will set me back $5,600. I could buy a supposedly low-mile engine from a very well-known West Coast Land Cruiser specialty supplier, but it will cost $7,200 plus core charge plus freight. I have looked into getting a used engine for around $1,500 (supposedly from a Cruiser that was wrecked with 42,000 miles), but I am afraid of buying a pig in a poke.

Then there's the option of buying a used engine that has been rebuilt. But then again, there's the issue of not knowing what you're getting. For example, I asked the supplier if the rebuild was done with a Toyota pistons/rings/seals kit, and he seemed strangely dismayed and confused.

Yet another choice would be to do a compression check and maybe just rebuild the top end and replace what needs replacing, including the oil pan gasket. The various choices-some with warranties, some without-are dizzying, literally.
Jason D. T.
Marietta, GA

A You're dealing with a modern-day family heirloom, Jason, so treat it as such. Keep the original engine and have it rebuilt by a qualified Toyota rebuilder with real Toyota parts. With this investment you'll have a practically brand-new truck, and your son can do the same rebuild when he inherits it. It's cheaper than buying a new Land Cruiser, plus this is the last of the solid-axle Cruisers, making it one of my favorites. Although I have not priced out this type of rebuild, your numbers put it in the middle of the options.

Jeep Junk or Jewel?
Q I have a Jeep '95 YJ Wrangler with 33s and a tired four-cylinder engine with over 250,000 miles. I have an older carbureted GM 305 that I would like to put in the Jeep. I've been told that none of the drivetrain is strong enough to hold the additional power of the V-8. Is this true? Will I have to change everything from the motor to the tranny/transfer to the axles? Can I get away with the engine swap? I keep getting conflicting answers, and my questions seem to spark heated debates.
Jake H.
Jasper, MI

A Your transmission is likely an AX-5, and your transfer case is probably an NV231 with a Dana 30 front axle and a Dana 35 rear. Though all are fine with a stock four-cylinder engine, the added torque and horsepower of the 305 will definitely max them out. Now, I'm sure there are guys out there who have a 305 with all the stock parts and giant tires and have no issues at all, but that doesn't make it right. For example, I have a friend who has a V-8 in his old Willys Jeep with the stock drivetrain. His T90 three-speed should have blown up by now, but he's a careful driver so it hasn't. If it were me, I'd replace at least the transmission to start and save up to replace the axles. I would change the transfer case last, as I think it's the strongest part in your drivetrain.

Nuts, I'm Confused!
Ups & Downs
Q What should I set my 4x4 suspension ride height or sag at? Modern dirt bikes all have about 12 inches of suspension travel, and all of the major manufactures recommend that the sag be set at roughly 4 inches (90-100 mm) or 33 percent of the total suspension travel. So basically, with the rider on board, the bike should sit with about 66 percent uptravel and 33 percent downtravel.

I have never seen ride height or suspension sag for 4x4s discussed in this type of detail. Everyone talks about how much lift they have or how much travel they have, but so far I have not seen any good information or "standardization" for ride height and sag on a 4x4 as it relates to total suspension travel.

I recognize that the ideal setup is probably different for a hardcore rockcrawler and Trophy Truck racer, but it would be nice to have a starting point.
Rich W.
Whittier, CA

A A vehicle's suspension moves in two main directions: down as the wheels drop into a hole or the vehicle comes off the ground in a jump, and up as the wheels go over an obstacle or the truck comes to a landing. I have found that most competitive rock buggies have a lot more suspension downtravel than up, and this is done to keep the whole vehicle low. However, these 4x4s are not very good at going fast, as the suspension quickly bottoms out.

Trophy Trucks and desert race vehicles aim for more uptravel than downtravel (droop) so they can soak up a big hit. Stock vehicles are close to the middle of the road, though they seem to err on the desert suspension setup. I like to run about 60 percent down/droop-travel and 40 percent up/bump-travel for my trail rigs, as this allows for good all-around suspension without getting too tall.

Desert trucks are often just the opposite at 30/40 down and 60/70 up (similar to a dirt bike), and dedicated rockcrawlers are closer to 80 down and 20 up.

This type of question tells me you are more interested in how a suspension works than in just clearing big tires, and that is important for today's four-wheelers. For this I'm awarding your letter this month's Nuts, I'm Confused prize: a set of General tires. General tires are found on a lot of different off-road vehicles, from desert trucks to rockcrawlers. General's new Grabber tire has been a big hit in the off-road racing scene, and you can get a set for your 4x4 if you're looking to explore the backcountry. For more info on General Tire check out

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results