Transmission shift ?

[Davis]

Another problem on my 1994 dually. The transmission will seem like it is slip shifting when it goes into overdrive sometimes but only under a load.It does not do this all the time. Is this a early sign of transmission failure or could something be replaced or adjusted ?The fluid is still red and not brown. I would appreciate any advice. Thanks Davis

[charliepeterson]

Try getting the truck scanned for transmission codes. Inside the pan on the forward side of the valve body is the torque converter solenoid. On the back side of the valve body is the 1-2 and 2-3 shift solenoids. If no codes look very carefully at the plug for the transmission harness, both ends for bent,corroded or loose pins. These transmissions are very good.

[Davis]

Charlie P,
Thanks for the reply. There are no codes.I am going to change the transmission fluid in the next week or so and will check on those componets. Thanks Davis

[arrowheadracing]

I have the same problem. Only under full throttle or close to it. The trans first started to slip only shifting into od. Now I notice it a little in the other shift of the gears. Under part throttle the shift is good and firm , so I know its not clutches. Are these solenoids prone to failure ? The trans fluid in the truck has been changed every 30,000 miles and the truck has 140,000 on it now. Its a 95 4x4.

Thanks

[charliepeterson]

Our fleet has many of these transmissions and they get the s*** kicked out of them and we don't see too many failures but the maintenance is very good. Yes these solenoids can fail and yes GM did have some issues with the first generation 4L80's in the internal wiring harness. GM upgraded the harness.
I would guess that over time we might see more issues in the shop but for the most part not yet. When you can't get a code from the ECM it is much harder to make it fail so you can "fix it right the first time".
The inside of the pan will really tell you what's going on in the transmission.