Transmission not shifting into overdrive

[Joe shmow]

I have 2002 Chevy Silverado with 4.3 engine.  After driving about 30 miles it shifts out of overdrive and will not shift back into overdrive. But if I stop, shut the truck off and let it sit for a minute, when I crank it back up its fine for another 20 or 30 miles.  Could this be a censor or something electrical?

[Jsdirt]

I'm not a transmission guru, but I remember the solenoids in the transmission on these models being a common failure point. Could be the 3-4 shift solenoid ... but only if the solenoid needs to be energized in order for 4th gear to be used. I've forgotten how these solenoids work. I do know if the 1-2 fails, it will start out in 3rd gear, so it's entirely possible the 3-4 works the same way.

[riverbanks]

Possible brake light switch failure?or is the engine struggling at all?

[ronrymanr]

Greetings I have been checking grounds. I have an internment shift problem that sometimes knocks out the speedo and rpm gages. The codes point to shift selinoids which were replaced. I did a hard reset and will give specific codes in another thread. Can you tell me where to find these ground atachment s are they all at the engine block? Im curious as to why the problem will reset not always by unhooking the positive side of the battery for a minute or 3? Thank you for your experience and help. 1995 k2500 Cheyenne i believe there are 16 bolts on my transmission pan. 350 engine.[emoji223]

 

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[Hillwood]

Clean and tighten the ground right below the driver's floor at the cab mount..
ALWAYS UNHOOK THE NEGATIVE BATTERY CABLE FIRST! You can't arc the positive then.

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[ronrymanr]

Is there a way to test shift selinoids when removed from the transmission?

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[Hillwood]

We have to start with getting codes.. How does the fluid look and smell?

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[swathdiver]

2 hours ago, ronrymanr said:

Is there a way to test shift selinoids when removed from the transmission?

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They can be tested on the transmission with a Tech-2.  This scan tool can also pull up the internal trouble codes that are most certainly stored in there since it won't go into 4th too.

[Jsdirt]

Not just a Tech 2, but ANY scan tool with bidirectional capabilities.

[ronrymanr]

Thank you

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