Not shifting properly

Tiny
CRAG63
  • MEMBER
  • 2005 GMC SIERRA
  • 4.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 130 MILES
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.
Saturday, August 24th, 2019 AT 1:04 PM

6 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Saturday, August 24th, 2019 AT 1:40 PM
Tiny
CRAG63
  • MEMBER
  • 4 POSTS
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.
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Saturday, August 24th, 2019 AT 3:01 PM
Tiny
CRAG63
  • MEMBER
  • 4 POSTS
Hi Roy. If it was the TPS, shouldn't I get a engine light or code?
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Saturday, August 24th, 2019 AT 3:05 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Saturday, August 24th, 2019 AT 3:30 PM
Tiny
CRAG63
  • MEMBER
  • 4 POSTS
Thanks Roy.
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Saturday, August 24th, 2019 AT 4:25 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You are welcome.

Always glad to help.

Roy
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Saturday, August 24th, 2019 AT 4:26 PM

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