Leak in the vaccume lines.
If you go to corvettemagazine.com and click on there tech link they had an article that tells you step by step with pics how to repair the headlight motors
Corvette Magazine Tech Articles has a step by step process including photos. http://www.corvettemagazine.com/2002/february/c4lights/light1.asp
in the front (driver side) wheel well under a 6x6 cover mounted to the wheel well facing forward there are 3 relays 2 are for the headlight motors left and right
Go to http://www.corvettefever.com/howto/33098/index.html. This gives full description for rebuilding C4 headlght drives.
The plastic gears in the headlight motors are weak. I had the same problem with my 1984 Corvette. You can get a new motor, but it's much cheaper to get new gears. Check out the C4 section at CorvetteForum.com for a how-to on replacing it.
General Motors, they have been the only one to produce the Corvette.
The Chevrolet Division of General Motors.
It is made by Chevrolet which is part of General Motors.
GM in U.S. (G.M. stands for General motors)
98-00 Trans Am Headlight motors reverseI bought some corvette headlight motors on eBay for my 98 and they work backwards, also the head light contol module looks Identical, but there again will make the headlights work backwards. Hope this helps.