Confused? E-mail your questions about trucks, 4x4's, 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
Question: Why is a U-Joint called a U-Joint?
Dave H.
Missoula, MT
Answer: Good question. U-joint is an abbreviation for universal joint, an age-old concept for transmitting power through a shaft with an angle. Every few hundred years somebody reinvents it and it is then named after them such that it has been known as a Cardan joint or Cardan shaft after Gerolamo Cardano in the 1500s. Then it was a Polhem knot after Christopher Polhem, or a Hooke's joint after Robert Hooke in the late 1600s. It wasn't until Henry Ford began making cars that it was christened the universal joint. Most of the people I talked to assume Ford named it a universal joint because it can be used in many different angles and applications in an automobile such as in a steering column, front steering axleshafts, or driveshafts. The universal joint is a strong way to transfer power from one shaft to another at an angle, but often the greater that angle the weaker the joint. This is why it isn't a good idea to force your axles to do excessive climbing or crawling when the front wheels are turned unless you are outfitted with strong U-joints.
Question: Why is a tire called a tire?
Tom Boyd
via 4wheeloffroad.com
Answer: A tire is called a tire because if you drive for a long trip on a set of tires, such as the long drive home from a great week of wheeling in Moab, you are bound to become tired. That's not really true, but it sounds good. Actually I think the truth is that tire is a derivative of attire such as clothing or accessories. Thus if you want to dress up your truck you need to find some better attire or better tires. I prefer my trucks to be dressed in something taller than smaller and usually in a dark blackish color with some sort of aggressive treadlike pattern.
Question: Why is a portal axle called a portal axle?
Dylan E
Corona, CA
Answer: Another great question! A portal axle is an axle that has gearing within drop boxes at the end of the axlehousings. These offer increased ground clearance but they also transmit the rotation force of the axle from one level at the axleshafts down to and out the stub shafts at the centerline of the lower gears in the portal drop box as can be seen in these photos of some prototype military axles. In researching the term "portal" I came up with a few definitions. First is one in the construction and architecture industry where a portal bridge or roof of a building has a top crossbeam supported by two legs at either end of the beam, similar to how the axletube is supported by the drop boxes.
Another definition comes from the science-fiction or fantasy literature where a portal is a magical or technologically advanced doorway between distant locations. This could be applied to the driving force being transported from the upper axleshaft down to the lower stub shaft through the portal gearbox. Though I doubt whoever named the portal axle was referring to some space odyssey/magic cave type thing when he was describing these axles.
By the way, I also found a heavy metal band in Canada named Portal, and many portal axles are heavy and made of metal, but the band only formed in the summer of 2000 and portal axles have been around at least since the '40s, if not earlier.
Finally I began thinking about how the power is transmitted into the axle at one level and comes out at another lower level and I realized that it is similar to a periscope in a submarine where you look in at one level and through a series of mirrors you can see out at a higher level. In fact, I think the proper term for portal axles could be periscopal axles, but I'm pretty sure no one would know what the heck I was talking about if I said that.
Question: I have a '77 Jimmy with a 12-bolt rear end, a Dana 44 front end, and an NP203 I think. I am not sure about what gears I have, but was thinking about changing them. Should I put the same gear ratio in both front and rear, or keep them different? If it is better to keep them different, then how far should I keep them apart?
Bryan
via 4wheeloffroad.com
Answer: You definitely want the same gear ratio front and rear, or as close to the same as possible, say within 0.03 points. So if you have 4.10s up front you would want between 4.07 and 4.13 in the rear. The only time you want different ratios front and rear is if you are running different size tires front and rear, but for the majority of folks, or other specified applications running the same ratio front and rear will work best so that the transfer case will not bind when locked in four-wheel drive.