SAND TIRES
I’ve been told by a local surf fishing guide that the A/T tires on his larger truck dig in too much thus making it easier to get stuck. The A/Ts currently on my Pathfinder work fine but I wonder about how your A/T tires will work in the sand on a Tundra 4x4 Double Cab standard bed.
Barry Mendelson
assume by “your A/T tires” you mean the two Pro Comp All Terrains that are available. Less aggressive tread patterns are generally considered best for sand... and I agree in principle. Using that criteria, the Pro Comp Radial All Terrain would be a better choice than the Xtreme All Terrain. In practice, having an adequate footprint for the weight of your rig counts as much the tread pattern. Overly aggressive tires will be more of a liability given an equal footprint. Because you can only fit so wide or tall a tire to your rig, being able to air down becomes key. You can double the footprint by airing down. My opinion is that most any radial off-road tire with a reasonably flexible carcass, driven properly and aired down significantly, can work adequately in sand. Driving technique counts for a lot. If beaches and surf fishing are your “thing,” then a less aggressive A/T with a big footprint and a flexible carcass is your huckleberry. These attributes combine everything that works well in sand into a tire you can drive on the street.
E-BRAKE LOCKER
I was told that if I set my parking brake just about half-way that it almost locks the rear end and aids traction. Is this tip true?
Jeff Young Orange County, CA
Well, it’s not true that it turns your axle into a “locker,” but it does help a little, especially if you already have a limited slip. The first rule of differential operation is that the average of the two wheel speeds will always equal ring gear speed. That applies just as much as when the vehicle is going straight, turning or stuck with one wheel spinning. Let’s say the ring gear is at 100 rpms for all the following examples. Going straight, the ring gear and both wheels are all at the same speed (100+100/2=100). In a turn, one wheel speeds up and the other slows down but if you average them, they are still equal (125+75/2=100). With one wheel on a rock and the other in goo, the spinning wheel will spin at twice the ring gear speed but averaged by two wheels, the rule still applies (200/2=100). The other differential constant is that torque takes the path of least resistance and flows to the tire with the least traction. The limited slip type diff works on the principle that if you apply some braking to that low traction tire it has to transfer some torque to the other side. Most limited slips do that with clutches splined to each axle to supply that braking force. If you slow that 200 rpm spinning tire from the example above to 150 rpm, then the other tire will now have 50 rpms more(and some torque) to play with. That’s what the parking brake does, it slows the loose tire down and helps transfer some torque to the other side. This works especially well with low bias (loose) factory style limited slips, when the difference in traction side to side exceeds the built in braking action of the clutches. The partially applied parking brake augments it. Back in the “old days” ‘wheelers would separate the two parking brake cables and put a handle on each. If the right wheel started to spin, they’d pull up on that handle and slow the wheel down, transferring some torque to the other side. Obviously, applying the parking brake will have limited effects and should be done only short term, but it’s a timetested trick that works. It does NOT work on true lockers, only open diffs and limited slips.
“NEITHER RAIN NOR SNOW...”
I have a ’99 TJ with 35 inch Pro Comps and a 6-inch Fabtech lift installed at the 4 Wheel Parts Indianapolis store. I would like your advice on the best lockers for my stock axles for snow/ice driving and the best gears for mainly road driving. I am a physician and have to get to the hospital in any weather.
Perry Griffith, M.D. Indianapolis, IN
I’ve got a prescription for you, Doc. Too bad I can’t write it out by hand and really make you work to read it. My semi-legible chicken-scratchings will go toe-to-toe with any M.D.! First off, you didn’t say which Pro Comp tires. The old-style mudders will be a handful on ice. The new style XTreme mudders and the XTerrains are better, but your best bets are either of the Pro Comp All-Terrains. I think the Xtreme A/T would get you the best combo of street and trail performance. As to gears, it depends on which engine you have. If you have a six, 4.10:1 at least, with 4.56:1 preferred. If a four, 4.56:1 minimum, with 4.88:1 preferred. Finally, as to lockers, I’d suggest the Auburn ECTED (www.auburngear.com; 260- 925-3200). It has a mild limited slip capability but will lock up 100 percent when you want it to. The mild limited slip capacity can be an asset during inclement weather street driving. The Detroit Truetrac (www.eatonperformance. com) is also a very ice and snow friendly unit, as I have found for myself. Of course, you could go with the legendary ARB Air Locker (www.arbusa.com; 425-264-1391) as well and be totally open on the street with the capability of being 100 percent locked when you want it. All of these can be used up-front, those with limited slip characteristics will cause your front driveshaft to spin and if it’s not angled and balanced perfectly, you can end up with a vibration. The cure for that is either a locking hub conversion (Warn/www.warn.com; 800-543-9276) or get that drive shaft perfect.
VIBRATION RANGER
The center carrier bearing on my ’93 Ranger wore out, so I removed the shaft and took it to a driveline shop. After I reinstalled it, I now feel a vibration that is at its worst at about 45 mph. I recently read in your “Corporate Clunkorama” in the August issue that I was supposed to mark the location of the U-joint bearing caps in the yoke. Could this be my problem and is it correctable?
Jason
It’s possible that’s your problem, though there’s more to it. All you have to do is unbolt it, rotate it 180 and try again. Try it at both ends separately. You may still find some yellow factory marks on the flanges. If so, align them and test. Do make sure that the flange is seated properly. I have heard of guys who got grunge between the two surfaces and had vibrations after... the bolts work loose then too! Also, make sure that none of the weights have been accidentally knocked off the shaft. If so, have the shaft rebalanced. You may have more going on, however. Two piece driveshafts are double trouble. You did not mention if you have a lift, which complicates the issue. You have three U-joints that have to be phased and angled properly to avoid vibration. The t-case and middle U-joints should be phased the same. The rear will be 90 degrees from the middle joint. I’m not sure if the slip yoke on a Ranger has a master spline, but the only way to get one of these driveshafts out of phase would be to have separated the two rear sections at the slip yoke and reinstalled them out of phase. When properly phased, the forward yoke on the rear driveshaft should be exactly in line with the rear yoke on the shaft. If the Ranger shafts have a master spline, it’s impossible to get it on wrong. If you have a lift, well, it’s about impossible to get the driveshaft angles right. Normally you’d lower the carrier bearing a skosh to minimize vibration. The Ranger setup is tricky because the carrier mounts on top of the crossmember, so you can’t just use spacers to drop it a little. To lower it on a Ranger, you must revamp the crossmember and all that attaches to it. Getting the three angles right involves a bit of guesswork and trial and error. Overall, with lifts, the easier solution is to go with a one-piece driveshaft. You could go with a custom shaft or a ‘98-up Ranger (or Mazda B) Extended Cab one-piece shaft (47 inches weld-toweld). It bolts right up. They come in steel or aluminum, steel preferred for a trail rig. You then need to modify the crossmember by removing the carrier bracket and also you have to clearance the fuel tank skidplate. With lifts, you sometimes have to relocate the crossmember forward. I’ll save some space here and refer you to a great Ranger resource. The Ranger Station (www.therangerstation.com) has a great tech How-To section, including one on this conversion.
THE HUB’S THE RUB
I have a ’99 GMC Z71 three-door pickup. The transfer case is push button controlled. How can I keep the front driveshaft from turning full-time? I think this reduces gas mileage.
Berry
The short answer, Berry, is that you can’t. At least until someone comes up with a locking front hub conversion... which I could not find. That said, the drag is fairly negligible. It might not even show up outside the normal error margin normally found when checking mpg. My only suggestion would be to put a slippery synthetic SAE 75W-90 gear oil in the front diff to reduce the drag even farther.
A CHANGE IN TIME
I have a 2006 Jeep Liberty CRD 4x4. Under the topic of oil change intervals, the owner’s manual only states time not miles. The vehicle is driven little, like about 4K a year. When I purchased the vehicle, the service manager, along with the service personnel, told me to go by mileage which is listed at 12,500 miles. They said, “See you in three years.” They said this because the vehicle is operated under “normal” conditions, it’s a diesel and comes with synthetic oil. I have a hard time accepting this. Do I go by what the Jeep dealership is telling me or should have it changed once a year (4K miles) or maybe split the time and have it changed every 6K miles, which is the interval for hard use?
Rhonda Kay, GA
Like you, I’m surprised that Jeep doesn’t have a mileage interval. Is it confidence or ignorance? The old three-month interval is overkill with today’s very good oils but there is a good reason for a time interval. Oil oxidizes, even as it sits, especially once it’s been used. Synthetics are a lot more resistant to this than conventional oils, so they can go longer, but it still happens. I don’t know what oil Jeep installed in your Liberty but I doubt it was designed to last three years. Maybe it would hold up fine... maybe not... but I doubt you want to be a guinea pig. Let’s be practical here. We don’t want to waste oil resources by dumping the oil too early. At the same time, we don’t want to risk having the oil go bad over time. In your humid climate, you are more at risk than someone in a dry desert climate. My opinion is the same as yours. Either do it at 6K (6,250 miles is the exact number) or annually. If you do it annually, spring time is the best time to do it... right after whatever passes for your “cold” season down there. Otherwise, wait until you hit about 6,250 miles. Either way, buy a top-brand synthetic, diesel rated (API CI-4) oil. You may want to read this and next month’s “Four Wheel Finesse” for more info on lubricants.
FUMING JIMMY
I have a ’77 GMC Jimmy and when I have the top off or the back window down, I get tons of exhaust fumes in the cab! Everyone I talk to says there is nothing that can be done. Is this true?
Roy Cole
I noted the same problem with my old ’83 Blazer. I observed two things, the first being that if your exhaust pipes exit out the back rather than to the sides, it’s much worse. I also noted that those roof air scoops they used to offer seemed to make the problem better. They fitted on the roof over the back window and kind of scooped air down onto the back window. I don’t know if they are still available. As a final observation, I have found that downturned exhaust tips seem to help also. From here, why don’t we put the call out to readers with K5 Blazers and Jimmys and see if they have any useful suggestions. I’ll post them in a followup.
BUDDY, CAN YOU SPARE A 35?
I have a Sierra and run 35x12.50-17 Pro Comps (34.4 inches) on 17 inch wheels. The gears are 3.42 (I’m working on that soon) which are not a big issue in flat Mississippi. The truck is a Z-71 with Autotrac. My concern is that the stock spare measures 31 inches. If I have a flat, will I damage anything running the smaller tire? How far can I drive on it and is it better on the front or rear axle? When far from home, a big tire is not always easy to find. Is it worth buying a used 35 inch tire as a spare?
Tony Gonzalez
It’s most definitely worth it to buy a matching spare, Tony. I’ll even go farther and suggest buying tires in fives (unless replacing with the exact same type and size of tire). That way, you can incorporate the spare into the rotation program and that really does add miles to the life of the tires by throwing in that fifth meat. That’s what I do. Ok, so I’m anal... but I always get more miles out of my tires than my buds. But I’ve also been low on bucks and only bought four, and driven with an undersize spare. If you are stuck with a smaller tire, put it up front and turn the Autotrac off. If your rig has locking hubs (yours doesn’t) unlock them. Yeah, it’s a pain in the wazoo if the flat is in back, but it could save your rear diff... especially if you have a locker or limited slip. It can overwork the rear diff, fry the clutches of limited slips and totally fritz lockers. Even up front, without hubs or CAD to disconnect the axles from each other, the front diff side and spider gears will be spinning in the carrier like an over-caffeinated hamster in a hamster wheel, but at least they won’t be under power. As to how far you can drive, if on a driven axle, as short a distance as possible. A lot depends on the size differential between the two tires side to side.
DAKOTA AIRBAG DEPLOYMENT DANGER
I ‘wheel a ’99 Dakota and was wondering about the airbags. How much does it take to set them off? I take some hard bumps and don’t want them going off unexpectedly.
Name unknown
There’s surprisingly little info on this. I’ve never heard of a single case of airbag deployment when ‘wheeling. It’s probably happened but it certainly isn’t common. The systems are sensitive to sudden deceleration, so a hard vertical bump shouldn’t set them off. A hard horizontal bump might, but a deployment would be more likely if it was a hard horizontal bump against a tree! All I can say is that based on what I’ve read, a freak airbag deployment offroad is remotely possible but not very likely. Unless you’re a Banzai type and then the odds go up.
CLICKING RANGER
I have a ‘95 Ford Ranger with the 2.5L four. Immediately when I start it up on cold mornings it will “click”. It does not do it all the time, but most times. It only does it with a cold engine. I don’t think it’s a lifter because I have run it for five minutes, shut it off, restarted it and it still did it. This also seems to eliminate that it’s an oil pressure problem.
Jordan J.
It might not be an engine problem (yet) but sounds like it could be an oil problem. It’s hard to diagnose a noise like this without being there, but a “clicking” noise that is evident cold but not hot is often a lifter. Not so much a bad one but one that isn’t getting enough oil. What viscosity oil are you using? You would do well to be reading the “Oil Finesse” series, part two of which is in this issue. If the oil grade is not suitable for the climate, the too-thick oil has a hard time being pumped and the last place to get oil is the upper end. And, yeah, it takes more than five minutes to warm the oil! My suggestion is to switch to a 5W-30 grade oil and try it out this winter. Synthetic oils, like Royal Purple (www.royalpurple.com) would help even more because they have very good cold weather flow characteristics. If you are in really cold weather, you might even try a 0W-30 synthetic. If you already are using the correct grade of oil for your winter, you could have a sticky lifter. There are a lot of additives out there that claim to work at clearing those problems up. I’ve never personally seen one work any better than simply going to a higher quality oil.