Question: I have a 1981 Datsun 310 with only 10,000 miles on it. The front tires are showing some wear and I was about to rotate them until an auto mechanic suggested that I not do so on a front-wheel-drive car. His theory was the front-wheel tires would wear out first and to replace just those two when they wear out. Is this sound practice?--D.M.K.
Answer: The proper procedure for rotating tires used to be fairly simple because it was uniform for almost all cars, but that was before front-wheel drive and before radial tires.
Today, you could do almost anything in terms of tire rotation and be in compliance with one or another recommended procedure. The important one you want to be concerned about is your manufacturer's recommendations, which appear in the owner's manual.
Nissan recommends tire rotation every 7,500 miles. It suggests you rotate all four tires in a crisscross pattern, with the rear tires going to the opposite sides on the front and the front tires going to the rear on opposite sides. In other words, your left rear tire would go to the right front and so on.
Incidentally, this procedure is a change with respect to the practice recommended when radial tires first came into wide use on automobiles. At that time, it was thought that reversing the direction of rotation, which occurs when you change a tire from the one side to another, would damage the tire.
Many experts now dismiss that concern with respect to modern block-tread tire design. The much less common rib tread design usually still follows that practice of not changing the direction of rotation. In any event, the manufacturer's recommendation is the key thing to follow.
Q: I purchased a 1985 Oldsmobile 98 with a V-6 engine in September. When driving around town, the transmission will periodically disengage with no warning. In a few seconds, it will re-engage. The dealer replaced the transmission governor, but the problem continues. What could be the cause?--R.M.
A: Although GM has had plenty of trouble with its transmissions, that particular problem is unusual. I would suggest that you make sure that the transmission is actually disengaging, because you may be mistaking a normal operating characteristic.
That transmission, a four-speed overdrive, has a system that allows it to "free wheel" when you lift your foot off the accelerator. It may give you the sensation that the transmission has disengaged, but it is designed to free wheel when the engine isn't supplying power.
In any event, a governor has little to do with keeping the transmission engaged. Its function is to control the transmission shift points. I suggest you go to a GM dealer with a good transmission mechanic and have it inspected.
Q: I own a 1972 Toyota Corolla with 156,000 miles on it. At 141,000 miles, I had a new clutch put in. My main problem is vibration that comes from the clutch. I'll accelerate to 40 miles per hour with only a slight vibration, put the car in neutral and the car almost shakes apart. It continues to vibrate at higher speeds. I have had the tires balanced, the front end aligned. How is this possible?--W.B.
A: The key thing is to determine whether the vibration is related to engine speed or road speed. If you bring the engine speed up to driving speed and you don't get any vibration, it is unlikely to be in the clutch.
You should reinspect the drive shaft and universal joints, which were disassembled when the clutch was put in. If they are incorrectly aligned or loose, they will cause the vibration you are describing. An imbalance in the drive shaft can be very difficult to detect.
Ralph Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.