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Buy diesel engine for big towing jobs

2012 GMC Sierra 3500 HD SLT

2012 GMC Sierra 3500 HD SLT Credit: Handout

Dear Doctor: We are looking for a new American brand truck and want advice on what to search for. We need a truck that would be good for towing a gooseneck 3-horse and combo living quarters with a GVW of 14,000 pounds. What would you recommend for the auto transmission, engine (preferably a gas engine), and gear ratio? We travel in several states and need a truck that can handle with ease the hills of Pennsylvania, West Virginia, New York and Tennessee. We're retired and ready to travel. Richard

Dear Richard: First, a gasoline engine would not be my choice. The diesel engine will do everything, plus more. The diesel engine is well worth the extra $7,500 or so. Today's diesel engines are quiet and have excellent performance and fuel mileage. The gas engine will struggle with a loaded trailer on inclines. The heavy-duty automatic transmissions are built to last and will perform as designed. If I were buying a truck to tow, I'd be shopping in the General Motors lineup. The reasons are many, including the ease of servicing the engine and room under the hood. A gear ratio of either 3:73 or 4:10 is most common and either will keep the engine in the power band.

Dear Doctor: I own a 1985 Corvette with 41,000 miles -- it's mainly a weekend driver. When starting the car the lights on the vehicle, including the dash cluster, flicker at idle. The flicker diminishes when the car is at operating temperature, although it is still detectable. The other electrical problem is the radio. Sometimes the only sound is a static buzz. I was told the problems are related to a weak diode in the alternator. What should I do? Howard

Dear Howard: The easiest way to rule out a problem with an alternator diode is to unplug the alternator and start the engine. If the flicker goes away, then the alternator could have a weak diode or an internal problem. I recommend a Bosch rebuilt or Delco replacement. It does sound like a faulty alternator. These mid-1980 Corvettes do have a history of dash cluster faults, as do the radios. The good thing is both can be rebuilt by a number of good companies, including BBA remanufacturing in Taunton, Mass., for the dash, and United Radio in N.Y. You can also go to Mid-America Corvette for replacement parts.

Dear Doctor: I own a 2009 Dodge Challenger R/T (5.7 Hemi) with the manual transmission and just 12,000 miles. The only modification is a Mopar cold air intake that was installed at the time of vehicle purchase. The filter is a dry element. When should it be changed? Also, I heard about a catch can for the engine (catches oil). I'm told that supposedly when you hit the gas hard the oil bypasses the P.C.V. and goes back into intake. Do I really need a catch can? Louis

Dear Louis: Your Dodge Challenger R/T is a great all-around car with lots of power from the factory and lots of add-on performance equipment that can be installed -- the most common are the fresh air intake and free flowing exhaust combined with a computer reprogramming. We've also installed many superchargers that add additional horsepower without any negative effects. As for adding anything else, I do not recommend it. On your air filter replacement timing, just use a light to make sure you can see the light through it. If not, then change the filter.

Dear Doctor: I own a 2000 Buick LeSabre with only 63,000 miles on it. In cold weather, when starting in the morning I get a very extreme thump in the entire undercarriage system that makes me feel like the transmission is about to fly right out of my car. For years I have been trying to get my problem solved with no success whatever. Two dealers and one good mechanic told me that this is a design flaw with no remedy, including replacing the catalytic converter. What do you think? Sal

Dear Sal: I doubt this is a design flaw. It sounds like the transmission is building too much pressure and causing the clutch pack to lock into gear and not simply glide into gear. I suggest you have an inspection of the fast idle speed and all engine and transmission mounts.

Dear Doctor: I have a 1994 Ford F-150 V-6 with only 66,000 miles. It has begun to burn way too much gas -- I am getting about 6 miles to a gallon. I have it serviced yearly and my mechanic hasn't found anything that needs repair in the gas system. I drive this truck about 50 miles a week. There is no leakage in the driveway or any sign that gas is leaking when parked. Is there a hose or valve that only opens when driving that is actually leaking out? Ginger

Dear Ginger: On vehicles built prior to 1996 the OBDI computer system has a limited ability to monitor engine functions and will not necessarily set a "check engine" light. Functions on your truck that can impact gas mileage are engine temperature, oxygen sensor operation, PCV system, fuel pressure and EGR valve operation. Normal items like the air filter and air filter inlet will need to be checked, as well as the ignition timing. Making sure the transmission is shifting into high gear, making sure the brakes are not dragging and the tires have proper air will need to be reviewed too. All of the above items will contribute to poor gas mileage. -- Junior Damato, Motor Matters

Junior Damato is an ASE-certified Master Technician. E-mail questions to

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