I have a 1985 GMC Caballero with a 4.3 V6 engine. When I start the car the RPM is close to 2000. As a result when I place the shift lever in reverse the car jerks. I have had to have the transmission overhauled as a result of this jerking. Is there any way to cut back the RPM to 1000 to prevent his problem?
The RPMs are supposed to be high at start-up on a cold day. Being 25 years old, I doubt the high RPMs at cold start up are the main cause of your transmission issues. After that much time, anything on this truck is liable to break at any time.
If this truck still has the carburetor, there should be a adjuster screw on the choke assembly to control the idle speed. If it is fuel injected, this is controlled by the computer, and there is no adjustment.