Overdrive Isses with Automatic Transmission

Q: Why won’t my automatic tranny shift into overdrive at wide open throttle?

A: It’s designed not to shift into overdrive if your foot is all the way to the floor. You must be at 2/3 throttle or less before the tranny shifts into OD. So when you hit the top of 3rd gear, you’ll have to let off the gas to allow for the shift. But putting your foot back into it will probably cause a downshift resulting in the same problem.

B and M makes a kit modified kickdown valve (part # 70237) which fixes this problem. It costs about $30 and can be ordered through the Summit or Jegs. GM also makes a modified upshift valve which it included in police packages and that part # is 8673948 and sells for around $15. This will allow the tranny to shift into OD at full throttle.