828790vetteman

1990 Coupe, L98, Automatic, with 54,000 miles

In the last month or so I have noticed that my Vette has been making a few odd sounds. The first sound is one made by the transmission, sounds sort of like a "squealing stretching sound" (tough sound to describe) when the transmission is shifted into reverse. It does not always make this sound, it seems to be at random times. The other sound that is bothering me I only seem to hear when it is cold out (during my morning commute). It seems to be coming from somewhere under the hood and sounds like a knocking sound, usually heard under light acceleration, I have not ever tried accelerating harder to see if it increases with rpms, but my guess is it would. I am afraid if I started to accelerate harder I might be making a mistake due to the fact that I don't know whats the source of the problem. I am at a loss to what these sounds are the car does not use any oil or leak any kind of fluids to speak of. Back in July every fluid was changed including the transmission. Since July I have put about 2,000 miles or so on the car so everything should still be good. Any help would be greatly appreciated on either of these two sounds.

Thanks Matt

85 500 horse

The first thing I would do is check to ensure your tranny fluid is filled up to the proper level. Make sure your car is level and is properly warmed up and running when you check it. It's possible that when the shop changed your tranny fluid, they didn't put enough in. The color should be a pinkish red.

That sound you are hearing under the hood might be pinging. Light pinging is not detrimental, but if it gets loud and very noticeable, there is a problem and that could lead to serious engine damage. If you're running regular gas, try putting a couple of tankfuls of premium in.

Also, if you're in a cool or cold climate and you're using the wrong grade oil, you could be hearing the lifters. If it's cold outside, make sure 10/30 is used.

Try these suggestions and see if anything helps.

828790vetteman

I have always run premium gas in my car, despite the higher prices. For the oil I currently have 5W-30 in there, I live in NC where we generally see high tempatures in the mid 40s to low 50s during winter, and lows in the low 30s. Also for the transmission I will have to check on the level of the fluid and get back to you.

Thanks Matt

FullShred

The first noise may be a bad u-joint. If so, the noise can usually be heard if you shift from drive to reverse and back again repeatedly.

Does the second noise kind of sound like clicking? If so 500 Horse is probably right - pinging. My stock '90 L98 always pinged a little bit under mild acceleration. If it sounds more like a knocking sound, it may just be a exhaust leak. That can make sounds like your engine is coming apart

Good luck

kenv

My `87 makes a wierd noise when I shift into reverse early in the morning. I was told that this was normal, & that it had something to do with the ABS.