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1999 Chevy Silverado Transmission
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dchuck
New User
Mar 13, 2013, 1:26 PM
Post #1 of 7
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1999 Chevy Silverado Transmission
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I have a 1999 Silverado 1500. 5.3 V8. Truck has around 150k on it. My transmission will shift in and out of overdrive when going down the highway, has since day one. Year and a half and tranny still drives just the same as when it started. When its cold out though, the truck will shift into overdrive and stay just fine but when its warm I have to play with the gas by pumping it a little when going down the highway. I ran seafoam through it, didn't help. What could the issue even be? Nobody around home can figure it out.
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nickwarner
Veteran
/ Moderator
Mar 13, 2013, 6:07 PM
Post #2 of 7
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Re: 1999 Chevy Silverado Transmission
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Has anyone checked the pcm for transmission codes? Is this truck doing this while empty? Do you have a heavy utility body or anything on it? Has anyone watched the datastream with a scan tool to see if the TCC clutch solenoid is being commanded on and off as this is happening?
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dchuck
New User
Mar 13, 2013, 6:20 PM
Post #3 of 7
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Re: 1999 Chevy Silverado Transmission
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Yeah a friend that works at a shop ran codes and cleared them and I can't remember what code e said. It does this all the time. Not utility body or anything. And no data stream has been watched from what he said. What codes should I be looking for or what in the datastream should I look for?
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nickwarner
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/ Moderator
Mar 13, 2013, 6:29 PM
Post #4 of 7
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Re: 1999 Chevy Silverado Transmission
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Any codes that come up, post the code numbers up here. While driving with a scan tool hooked up, you want to see the command PID for the TCC lockup solenoid. See if it is coming on and off when your rev changes occur or not. If it is, the PCM is commanding it to. If not, the trans is doing it on its own.
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dchuck
New User
Mar 14, 2013, 7:38 PM
Post #5 of 7
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Re: 1999 Chevy Silverado Transmission
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We drove down the road with it plugged in and never got it to act up. Mainly because its cold outside. I watched the screen and as soon as it got to the point where it shift into over drive it showed tcc engaged and I'm sure that would say no when it kicks out.
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nickwarner
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/ Moderator
Mar 15, 2013, 2:36 PM
Post #6 of 7
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Re: 1999 Chevy Silverado Transmission
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guessing what it would read and not getting the truck to duplicate the issue isn't going to help you diagnose this problem. Everything tests fine when the problem isn't occurring. You need to get it to act up and be able to see that data pid to be able to diagnose which direction to take.
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dchuck
New User
Mar 15, 2013, 3:00 PM
Post #7 of 7
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Re: 1999 Chevy Silverado Transmission
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Ok ill have to wait till it warms up just a little bit because that's when it only acts up.
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