Stock 94 CD Player

[38camaro302]

I got a buddy's stock cd player from his 94 z28 when he bought my system from me. The connectors on the back are all the same and it worked fine in his car. When I try it in my car everything works, and it plays. The problem is that the volume when it is at the very MAX only sounds like its turned down real low. It is not as loud as it should be. Also, my speedometer doesn't work when it is hooked up in my car. Why is this? My stock cassette player works fine in my car. Anyone know why this is?