Question: I usually downshift through the gears to slow down my car before applying the brake. I figure I will save brake wear this way. Will this harm anything?--E.J.
Answer: You will cause less wear on your brakes, but you're more than doubling the wear on your clutch. If you wear out your clutch, you'll wish you only had worn out the brakes. A new clutch can cost several hundred dollars, whereas a good brake job for four wheels will cost $150 or less.
Using the transmission to slow the car is advisable only on long, gentle grades, where you are not constantly downshifting in and out of gears, such as when you approach a stoplight.
In addition to wear on the clutch, it's not sound practice to cause the engine to increase its speed drastically from idle to very high rpm. That goes for using the transmission on hills, as well. Watch that red line.
Q: I have a 1974 Chevrolet Suburban with a 454-cubic-inch engine. It runs great in normal street driving, but when it is necessary to accelerate up a grade, the engine sputters and coughs as though it is not getting enough gas. I have rebuilt the carburetor, put on an electric fuel pump and checked all the fuel lines for leaks, but to no avail. Any suggestions?--C.D.V.
A: Your assessment that the engine is not getting enough gas may very well be correct, but it is possibly that the problem could also be too much gas. If the engine is spewing black smoke, it's probably flooding due to too much fuel.
If you have installed an electric fuel pump, it should have been located at the rear of the car, near the gas tank. You should also have installed a pressure regulator, so that no more than six pounds of pressure is being delivered to the mechanical pump.
Excessive gas pressure can force gas past the shut-off needle in the carburetor float bowl, leading to gas flooding of the engine.
If the engine is not spewing black smoke and you feel confident the problem is lack of gas, you might check to see that fuel filter is not clogged or that the rubber fuel line is not crimped.
It is also possible that the fuel float is set too low, keeping too small a reservoir of gas in the carburetor. That would be adequate for level driving, but when the engine demands extra fuel it wouldn't be there.
Q: I own a 1983 Honda Accord Hatchback. It seems to vibrate and shake after I drive it for a while in the morning. It also seems to do it when I park downhill. I've taken it to several places and nobody seems to be able to find the cause of the vibration. What would cause this?--M.H.
A: Such a vague problem could be caused by a problem in the engine, suspension or clutch. If you really want the problem fixed without wasting a lot of money muddling around, you're going to have to be more specific when you speak to your mechanics.
The problem you describe could very easily be clutch chatter, a problem that occurs when you are shifting gears on a manual transmission. It results when the single friction disk inside the clutch vibrates between the two metal pressure plates.
It just as easily could be engine mountings that are vibrating at certain engine speeds. Or it could be an engine that misses at certain warm-up temperatures. Many engines go through a period of roughness during their warm-up.
You should have had a Honda service mechanic inspect the car to make sure the vibration is not safety related, such as if it is a loose engine mount. Unless this vibration is severe or causes a stall, it may be nothing more than an aggravation that you'll have to live with.
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.