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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 35
by Bob Hagin
Q. I own a 1995 Chevrolet Impala SS and recently the owner of another SS stopped me and asked if I had my factory differential gasket changed. He told me of failing axle bearings and directed me to the Impala web site for more information. My dealer refuses to acknowledge that there is any problem and says that G.M. has never issued Technical Service Bulletins or other alerts on this topic. My SS is not a car I use every day and I reserve it for long drives and therefore I have only 12,000 miles on it. In the print-out I got from the Impala website, it gives the part number of a suitable Fel-Pro gasket to replace the original G.M. part. Should I get one and have my dealer install it or is it already too late? I don't hear any strange noises. Of course I'll have to pay, since G.M doesn't acknowledge the problem. I'm hoping you will have other "sources" which will give you the real word on this matter.A. Alldata, the on-line repair time source, says that the retail time to remove and replace the gasket is .5 hours on a warranty and .8 hours retail. For the answer to whether a problem exists, I called the Tech Information desk of Fel-Pro, the manufacturer of the gasket in which you are referring. I was told the problem is that the original equipment gaskets don't have "holes" in them that allow differential oil to "mist" down the left and right axle tubes and provide suitable lubrication for axle bearings. Under medium or hard use, the bearings apparently fail, then produce a grinding noise from the differential. Since the bearings ride directly on the axle shafts, they go too. As an aside, the tech rep said that Fel-Pro sells 150,000 cover gaskets for the 8.5-inch "big" differential alone. A qualified mechanic can do the job but be careful that it doesn't void your warranty.
Q. About 18 months ago I bought a clean '87 Cadillac Cimarron with 93,600 miles on it. It has a digital oil pressure indicator that reads in segments of 10. The oil pressure is under 40 PSI at idle but as the engine speed increases, the pressure goes right to the top and stays at 80 during driving. Some guy suggested that it's the oil pressure sender. This car uses oil, about a quart in 500 to 800 miles. What causes this? is there a danger the engine will be damaged from high oil pressure? Four months ago, a mechanic reattached an automatic transmission wire that had been disconnected. A week later at a stop sign, the transmission locked up and it wouldn't move. I had the wire disconnected again and there's no trouble now. I've been told the problem is in a solenoid and the torque converter. Should I report this to the manufacturer? Do you think they should fix it?
A. After nearly 100,000 miles and more than one owner, I don't think Cadillac will be willing to help you. If you have it fixed, your fuel mileage will increase a bit but that's about all. Have a mechanic install a test hydromechanical oil pressure gauge to see if the pressure is actually 80 or if the sender is bad. High pressure usually isn't a problem unless it gets around 150 and than it could blow out some gaskets. The problem may be a faulty pressure relief valve.
Q. I know that all modern cars and trucks are computer-controlled and so is my 1995 Plymouth Neon. It is many miles over the warranty limit at 65,000 and I'm concern that the infamous Y2K "bug" will affect my car when it's computer reaches the year 2000. Am I going to have trouble and should I have something done about it before next January?
A. The consensus is that there will be no Y2K "glitch" in cars and trucks when the change-over occurs. It would only happen if a vehicle maker used a two-digit date coding which would result in the computer reading "00" or zero year. Chrysler products have used four-digit codes.
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