Question: I have an '03 F-250 Super Duty with the 6.0L diesel hooked to the five-speed Torque Shift transmission. Thus far I have installed the leveling kit to raise the front end, installed a turbo timer, rear airbags, 35-inch tires, and a K&N air-intake system, along with an auxiliary bypass oil filter. My next project is to work on the exhaust system. But I am getting mixed signals as to whether I should get a turbo-back system or an after-cat system. I live in central Utah and have to retain the catalytic converter to be legal. A lot of the aftermarket systems eliminate the cat altogether, but I have found a few after-cat systems. No one I've talked to can give me a horsepower difference between the two types of systems. My local exhaust shop told me that if the cat has to be retained, the factory 3 1/2-inch downpipe is just as good as any aftermarket 3 1/2-inch downpipe with the factory cat. What's the deal?
John Andrews
via 4wheeloffroad.com
Answer: Here's the deal: Catalytic converters are more restrictive than a section of straight pipe of the same diameter. Very few states emissions-test diesel vehicles on a yearly basis at this time, so some truck owners remove the factory catalytic converter to improve exhaust flow. It's illegal-but it happens. Diesel trucks used in competitions should remove the cat because the excessive fuel that gets pumped out the exhaust (that makes the black smoke) could cause it to plug up over time.
That said, we think you should keep your cat and add an after-cat exhaust system to your truck. It's up to you whether you replace the factory downpipe you have now with an aftermarket piece. They typically will flow more, but as your exhaust shop said, you probably won't feel the difference with the cat in place.
Question: I have a '90 Jeep Wrangler YJ with a four-cylinder engine and five-speed transmission. I want to run 33x10.50-15 tires with about a 4-inch suspension lift. What I would like to know is what axle gears and locker should I put in the factory axles to handle these tires for general wheeling and daily driving? Do you think I need hydraulic ram-assist steering?
Mike Garland
Conway, AR
Answer: A set of 4.88 gears and a rear Lock-Right (864.843.9231, www.powertrax.com) would be just about perfect for your combination. It would give you a 2,300-rpm cruising speed at 55 mph in Fifth gear, a 50:1 crawl ratio, and enough grunt to cruise around town without killing the clutch. Plus you'd have the added traction of a rear locker-without a huge investment in a rear axle that you'll outgrow if and when you move up to 35-inch tires.
I have a '99 Jeep Cherokee. It has a 4-inch suspension lift and a small set of 30x9.50-15 Dueler AT Revo tires. I have run into a few problems with it when certain parts of the engine get wet when I'm out playing. I have lost two alternators (due to drowning) and one computer for my transmission. The alternators where lost in part due to their location at the bottom of the engine. The transmission computer was lost when the hood was covered by water. I know submerging the Jeep in water isn't good, but it does happen. What can be done to protect vital parts from too much water?
FC Marshall
Milesburg, PA
Answer: If you can't keep your Jeep out of the water, you're going to have to keep water out of your Jeep. First let's think about where the water is coming from. When you splash through a mud hole or water crossing the tires spray a huge amount of H2O (under high pressure) in every direction. Your engine's cooling fan and serpentine-belt system can also pull a ton of water into the engine compartment and throw it all over the place. You can't seal everything in a waterproof bag, but you can help direct and deflect some of the water away from the vital components. We'd try using large rubber mud flaps as shields that cover the space between the bottom of the radiator and your Jeep's oil pan. What you want to do is make it harder for water to come in, but still give it a way to drain out. Our other tactic would be to convert the Jeep to a set of electric cooling fans that you can turn off just before you enter the water.
Your alternator problem is common, but often it's the grit in the water that kills them-not just the moisture. Get in the habit of carrying a can of electrical parts cleaner (available at any auto parts store) and flushing your alternator out after every off-road trip to prevent damage. We'd also think about relocating the alternator to a higher place in the engine compartment. Unfortunately we know of no aftermarket kits to do this.