Transmission issue

[Phillip]

I have a 91 C2500 5.7L 2wd. From what I looked up it has the 4l80e in it. When the transmission warms up after about 5 miles, it will downshift into 3rd gear and won't shift back into 4th. After I park and turn the truck off and then start going again. It will shift fine into 4th then after a few miles starts doing the same thing again. There is no service engine soon light but I jumped the connector to pull any codes. I'm getting a code 85 which is a prom error. What could the problem be? I read it could just be the input speed sensor that's bad and the problem might go away if I replace the sensor.

Sent from my SAMSUNG-SM-N920A using Tapatalk

 

[BIG_KID]

91 should have the 700R4
TV cable controlls the trans
How's the 1-2 and 2-3 shift

 

[Phillip]

91 should have the 700R4
TV cable controlls the trans
How's the 1-2 and 2-3 shift

No, the rpo codes says it's a 4l80e. I also double-checked and its a 17 bolt pan. The 1-2 and 2-3 shifts are perfect. I read that it's probably a faulty input speed sensor on the transmission

Sent from my SAMSUNG-SM-N920A using Tapatalk

 

[BIG_KID]

Oops, your right. Sorry