4L80E Coming out of OD

[DAtchley]

I've done the search and don't seem to find exactly the same thing for my year.

Now the transmission is behind a 1993 6.5 TD 2-wheel drive dually. Mechanical Injection.
Newer TPS already. 100k miles, 4.10.

I keep losing Overdrive. I can shut down the engine and get it to reset most of the time. But yesterday the temperature outside was 85 and it would not stay in OD at all.

It will be fine in the cool morning air and all the way to work (40 miles).

Coming home on warm days (+75) the transmission will start off with a HARD shift between 1st and 2nd. And the shift points are higher too I believe.
When this happens I already know I won't have OD. Mostly I started to just put it in neutral and turn off the key for 10-15 seconds.

Sometimes it will start to "hunt" when I'm speeding up, then just dump the OD. In the warmer weather yesterday it would just slip out of OD for no apparent reason for the short time I could get it engaged. Sometimes it will be fine until I come to a stop because of traffic and then I'll feel the hard shift to 2nd and I know I'm not going to have OD again.

This problem has been with the truck for at least 5 years or more. I just started to use it as a daily driver recently and noticed the effect the warmer outside temperature had.

Thanks

[midniteplowboyy]

Flash the codes, put a jumper wire across the "A" & "B" terminal of the diagnostic connector under the dash, turn the key to run position and count flashes from the service engine soon light.

You'll probably come up with, transmission component slipping , or something like that.

Mine had, code 68 Transmission component slipping, it will set this code if the TCM sees 50 rpm slip between engine rpm and imput shaft rpm for more than two seconds in OD with TCC locked IIRC. Mine was a bad converter.

Flash the codes, lets see what you got, maybe its just a solenoid or wire.

[DAtchley]

The only code I have right now is 22.

I have set the voltage on the Throttle Position Sensor to .5 volts at idle.

If it matters, this rig only has 107k miles, and has been used for light duty it's whole life. New engine from the dealer at 45k.

[Magnum97]

i had the same problem, a new tps solved it for me.
could be driving down the road just fine and at random it would jump out and not go back in, and for the first few months i could pull over, shut it off and restart, all would be well. finally it would no longer reset and go into OD, i replaced tps and all was well.

[stingthieves]

tps -- AND Replace the ignition switch also

Power and ground is everything

[DAtchley]

So I went back and reset the voltage at the TPS to exactly 0.5 volts at idle.

Then I decided to go up the street and have the Tranny fluid changed. BUT the thing would not even shift out of 1st! Damn, I thought. I'm working backwards on this thing.
I went over every connection and checked for something left off or loose.

While doing the connector checks I noticed that the "parking brake" indicator seemed to be on.
However, it was only dimmed. But not related to the parking brake. Just on slightly for no apparent reason. I happen to be somewhat electronically educated, and knew something was creating the path through this source, perhaps due to a bad ground on something.
I wiggled some connections in the fuse panel and the light went out. Cleaned everything up, and went for a test drive.

It works smooth! All gears, OD, even in warm weather.

Thanks to everyone that has posted on this topic. It gave me a great start on troubleshooting.