Question: I've read different articles/columns in the magazine over the years about tires, but I'm still not clear on one particular point: How do I, as a layman, know when I can mix and match tires? Any idiot should know that all of the tires have to be the same size. But some articles have suggested that one should make sure that all four tires come from the same manufacturer, have the same tread pattern, and so on. Is all of this to avoid binding in the transfer case? There are times when I still have two good used tires left from one set and two good used tires left from another set. Can't I run them together?
Brent Baker, Columbia, MO
Answer: In a perfect world we'd all be running on brand-new tires that were all the same make, model, and size. We'd never drive anywhere without making sure all four were inflated to the ideal pressure, perfectly balanced, and aligned properly. But by the very nature of a lot of our 4x4s-this never happens.
The tires are arguably the most important part on your vehicle, so it's not a place to cut corners. As a rule you should run the same size tire in all four positions. You should not mix radial and bias-ply tires, and if you have directional tires, they should roll the direction the manufacturer intended. If you're going to mix and match tires on your 4x4 the best results come from putting the matching tires on the same axle. We'd put the better tires on the front because they're the ones that stop and steer your vehicle. They're also the ones that you'll feel vibrating the most if they are out of balance.
Question: I have a '73 FJ-40 with a Rancho 2 1/2-inch spring lift, a shackle reversal, a Chevy 350 engine, an SM420 transmission, a 2-inch body lift, and 35-inch Pro Comp Xterrains. I'm not happy with my spring's articulation. I have a friend with Old Man Emu springs that perform much better than my Ranchos. Is there anything that I can do to help them? I have been told that Rancho springs for the FJ are junk and I should just toss them. But I can't afford to replace at this time. I remember reading something years ago about opening the spring wraps. Is this a good idea? If so, I have four wraps per spring, which ones do I open? Any help would be greatly appreciated.
Robert Castle
Tucson, AZ
Answer: You can make any leaf-spring pack perform better off-road with a little massaging. You can try opening up the spring clamps on your Rancho springs to see how they respond. But if you pull all four clamps you'll most likely wear the springs out as they may flex too much. We'd try removing the clamps behind the axle first. Leave the ones in front of the axle in place because they limit axlewrap. You could also try disassembling the leaf springs and sanding and painting each leaf to reduce internal friction of the pack. We've found that rubber bushings in the spring eyes will let the pack twist more than urethane bushings, but they won't last as long either.
Question: What's the best gearing for my '97 Dodge Ram 1500 4x4 shortbed? The factory tag under the hood says that I have a 3.50 axle ratio now. The truck has a 5.9L V-8 with a four-speed automatic transmission and a Dana 44 front and 9 1/4 rear axles. The truck has about 140,000 miles on it and I bought it with a Superlift 5-inch suspension lift and a 3-inch body lift. It rides on 37x12.50-15 Super Swamper SSRs.
Jeff Button
Sgt. 1st Class
Fort Irwin, CA
Answer: A lot of it depends on how you're going to use your truck. If Dodge is putting 4.56 gears under its new Power Wagon, and that truck has 33-inch-tall tires, we think you should go with at least low, if not 4.88s. We have experience with a '94 Dodge that has 37s with 4.56 gears, and it feels pretty strong, but its engine has been modified pretty heavily.
Question: I'm looking to get a 4 1/2-inch Rough Country lift kit for my Jeep Cherokee XJ. Rough Country's Web site says I need a slip-yoke eliminator kit and/or a constant velocity (CV) style front driveshaft. But I have no idea what either of these things are or where to get them. The site also says I might need to extend my rear driveshaft. Are there special kits I can buy to do this or are there special shops I can bring the truck to?
Austin Mathews
Ironwood, MN
Answer: A slip-yoke eliminator (SYE) kit is used to convert the rear output shaft of your Jeep's transfer case to use a bolt-on U-joint yoke, instead of the slip-yoke style it has now. The upside to this conversion is that it permits the use of a longer rear driveshaft to handle the extra driveline angle caused by the lift kit. An SYE also makes it easier to use a CV style driveshaft to further reduce driveshaft vibration. An SYE kit for your Jeep's NP231 transfer case is available from Currie Enterprises (714.528.6957, www.currieenterprises.com), Advance Adapters (800.350.2223, www.advanceadapters.com), Teraflex (801.288.2585, www.teraflex.biz), and JB Conversions (337.625.2379, www.jbconversions.com). Your local yellow pages will list a local company that can make you a new driveshaft (or two).
Question: Recently my '90 fullsize Ford Bronco with 237,000 miles on it had some rear brake problems. I took it to a mechanic who told me that my rear differential axle oil seals had failed and wiped out the rear brake shoes. He said he could fix the brakes, but not the seals because there was a bolt broken in my axle that would prevent him from removing the axleshafts, and replacing the seals.
He told me I could drive it home (after he redid by rear brake system) but the axle seals would still leak. Should I try to fix the axle I have? Or get a new axle with a locker in it?
Nathaniel Canales
Corpus Christi, TX
Answer: This is a very common headache with C-clip axles. One way or the other, you're going to have to fix the leak. The gear lube dripping past the seals is likely what caused the brake shoes to fail in the first place.
You could certainly buy your way out of the problem and get another 8.8-inch rear axle to replace the one you have. But we'd at least try to replace the axle seals in your current axle first. To do so you need to remove the center block that forces the axleshafts apart and remove the axle C-clips from both axleshafts. But to do that, you're going to have to remove that bolt in the differential. It's a hardened steel piece, so they have a tendency to break as you described. First we'd try using a broken-bolt extractor kit (EZ Out). Drill the center of the broken bolt with the recommended size drill bit, and then try to back the bolt out with the left-hand thread extractor in the kit. Be careful, because it is very common to break the extractor off inside the old bolt.
If the extractor breaks, or doesn't work, we've seen people drill out the entire bolt with a left-hand spiral drill bit, and remove the center block. If you damage the case taking the bolt out you'll need to replace the carrier. A stock carrier sells for around $150 at the dealer, so it would be a good time to install the Detroit Locker (800. 328.3850, www.detroitlocker.com) or ARB (425. 264.1391, www.arbusa.com) you always wanted.