Not shifting properly

2005 GMC SIERRA
130 MILES • 4.8L • V8 • 2WD • AUTOMATIC
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CRAG63
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I went from a stop to hard acceleration, at about 35 mph the engine bogged, I took my foot of the gas and floored it again and the engine over revved. Now the truck wont shift out of first until about 35 mph. when going down the highway it stays in third until you left of the throttle.Then it will shift to overdrive, but as soon as you push on throttle it goes back to third.It still shifts smooth but I have basically have to shift out of first with my foot, like a manual.There is no engine light on and no codes.
Aug 24, 2019 at 1:04 PM
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ASEMASTER6371
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Good afternoon.

I would first suggest changing the fluid and filter. See if there is any debris in the pan on the magnet.

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

The throttle position sensor is the key sensor to transmission shift points. If you damaged the sensor from the hard pedal push, it would affect the operation.

https://www.2carpros.com/articles/automatic-transmission-problems

You need a scan tool that will monitor the signal from the sensor to the PCM.

Roy
Aug 24, 2019 at 1:40 PM
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CRAG63
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Hi Roy, when I put the truck in second it stays in first and wont shift at all even when I let off the gas.The mechanic who used a hand scanner and didn't get a code. took it for a drive and said it was the solenoid, why no code a broken number 2 band? The oil isn't burned and the color is good. the transmission was serviced 30,000 miles ago.
Aug 24, 2019 at 3:01 PM
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CRAG63
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Hi Roy. If it was the TPS, shouldn't I get a engine light or code?
Aug 24, 2019 at 3:05 PM
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ASEMASTER6371
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If it was a solenoid, yes, you would have a code.

If it was a band, no there will be no code. That is mechanical. There are no codes for mechanical failures.

No to the TPS. It could still be in adjustment but sending a wrong signal.

Roy
Aug 24, 2019 at 3:30 PM
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CRAG63
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Thanks Roy.
Aug 24, 2019 at 4:25 PM
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ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
Aug 24, 2019 at 4:26 PM