I have a '97 Ram 1500 Sport 4 x 4. Over 120k miles. Driving on highway about 60 mph. Noticed overdrive light is on; tried turn off by pushing O/D button. Light would not turn off; transmission wouldn't shift on take offbut only once. RPMs up; transmission overheat light comes on then check engine light. Drive to nearby shop (families). Father-in-law looks at truck & drives and eventually gets the same problem. Code comes up bad sensor of some sort; replaced sensor. I drive again and not 5 miles problem happens again.

Question: has anyone had this problem? Is it a bad transmission or a simple speed sensor? Or a bad O/D switch? We can't seem to find the problem and don't want to replace the transmission if it doesn't have to be. Thanks.

DPJ