I have a 2004 Z71 with the 5.3 engine. About a week ago i backed in my drive, opened my gate (left truck running) , got back in to back up and I had no reverse, drive or 1,2 or 3. I turned the truck off and cranked it back up and all gears were there, everything worked great. Went down the road, pulled into a parking-lot to unload some materials, put it in park, unloaded materials (left truck running), got back in and again no reverse, drive or 1,2,3 - turned truck off and cranked it and all the gears were back, everything worked great. Before this first started happening I have had no issues at all with the transmission, this came out of no where. Would appreciate any help I can get. Thank you

 

First check for trouble codes, even if the CEL isn’t on. Almost any parts house will check codes for free if you don’t have or want to buy a code reader.

Regardless of codes or not, disconnect the negative battery cable and then remove the transmission connector for inspection. It’s on the right rear of the transmission, just above the pan and behind a heat shield. A pair of long reach 90* needle nose pliers make removing it very easy.

Inspect for signs of transmission fluid inside the connector - this is a well known problem and can cause the issue you describe. If there’s any fluid residue at all, the internal wiring harness needs to be replaced which is easy to do by dropping the pan.

If you’re not sure that fluid has leaked into the connector, clean it with electrical contact cleaner and compressed air, then drive the truck for 10-15 minutes and check again.

If the connector looks clean, inspect the harness between the trans and PCM for damage and repair as necessary.

Also check that the shift cable end is in good condition - the bushings can wear out and prevent the manual shift lever from engaging the correct position inside the trans.

 

I am out of town working but as soon as I return home I will do all that you suggested and report outcome , Thank you