"99" 2500 Tranny Problem

2500 guy · 03-06-2007, 01:18 PM

Hey everyone, just bought a used 99 2500 4x4 silverado with the 6.0 liter motor. Have noticed that there is a malfunction in the Tranny.. It seems to take itself out of overdrive and downshifts to 3rd gear, and When it drops out of OD to 3rd, it starts shifting really hard in 1,2,&3rd on take offs.. The tranny won't go back to overdrive and shift well until the truck is turned off long enough( about 30 seconds) to reset the onboard computer... It seems to be triggered easily by towing any load, or driving into a stiff head wind..There are no error codes stored in the computer. I Have changed the TP sensor on the throttle body and cleaned it , but no other sensors. Any ideas or experiences out there that can help me diagnose this problem would be greatly appreciated. Should I change the Vehichle Speed Sensor,and which one should I start with If I do( 1 external 2-internal)?Thanks---2500 Guy

mrjohnwayne · 03-06-2007, 02:45 PM

Might want to check the alignment of your PRNDL switch. It is located on the tranny where the shift lever goes into the tranny. There will be 2 marks that must be lined up while in park. Not sure but a suggestion.

chevyguy · 03-07-2007, 10:22 PM

Run the codes, I alomost bet its your TPS. Had it do the exact same thing in my 97

03-06-2007, 01:18 PM	#1
2500 guy Junior Member Join Date: Mar 2007 Posts: 1	"99" 2500 Tranny Problem Hey everyone, just bought a used 99 2500 4x4 silverado with the 6.0 liter motor. Have noticed that there is a malfunction in the Tranny.. It seems to take itself out of overdrive and downshifts to 3rd gear, and When it drops out of OD to 3rd, it starts shifting really hard in 1,2,&3rd on take offs.. The tranny won't go back to overdrive and shift well until the truck is turned off long enough( about 30 seconds) to reset the onboard computer... It seems to be triggered easily by towing any load, or driving into a stiff head wind..There are no error codes stored in the computer. I Have changed the TP sensor on the throttle body and cleaned it , but no other sensors. Any ideas or experiences out there that can help me diagnose this problem would be greatly appreciated. Should I change the Vehichle Speed Sensor,and which one should I start with If I do( 1 external 2-internal)?Thanks---2500 Guy

03-06-2007, 02:45 PM	#2
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,221	Might want to check the alignment of your PRNDL switch. It is located on the tranny where the shift lever goes into the tranny. There will be 2 marks that must be lined up while in park. Not sure but a suggestion. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

03-07-2007, 10:22 PM	#3
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	Run the codes, I alomost bet its your TPS. Had it do the exact same thing in my 97 __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

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