Questions and Answers

Chevy Silverado Dropped Oil Pressure Q. Vincent, I have a 1994 Chevy Silverado, 5.7 liter, 2WD, automatic transmission. P/S, A/C ABS, engine mileage approximately 8,000 miles. My situation is this: recently, while driving a four and a half hour trip, at up to 65 mph, all is well. When I accelerated to 70-75 mph (interstate), at around 2,300 to 2,400 rpm, my oil pressure started to fall off from 40 to 50+ psi, high volume oil pump, replaced a year and a half ago, to roughly 10 or so.

Backing off throttle below 2,300 to 2,400 rpm range restored oil pressure to normal. No dash light came on. With vehicle in park, there is no drop in oil pressure at higher rpm. Mechanical gauge and factory electric gauge match in all respects. All other parameters normal. Oil changes performed routinely. This is the first time I have ever encountered a situation of this nature, my own, or anyone else.

Appreciate your thoughts and expertise,
Claude

A. Is it possible that the distributor gear is starting to free-spin on the shaft? Maybe the roll pin is broken? I guess it would have run pretty bad if that happened. Either a bearing is coming out of place or the pump has a problem. I've seen a cam bearing walk out of place and cause oil pressure to drop. Could be an oil pressure sending unit starting to go bad.