Can I use the cruise control , from a 1994 plymouth voyager, onto a 1989 plymouth voyager?

I have a 1989 plymouth voyager, 2.5 engine size, automatic, I am having problems with the cruise control, when I,m driving 65 mph, it will work, but then slowly it would decrease speed, then I gotta keep pushing the cruise control, every 3 seconds to keep it to hold the same speed, why, is it doing this?can I exchange the one from the 1994 plymouth voyager, 3.3,engine size