Topnos

I really need your advice.

I have a 06-2500-4x4 (with a 5.9 and a stock auto transmission) at around 85,000 miles. About a month ago I started to experience the shuttle shifting phenomenon. I replace the governor solenoid and the truck shifted great for a day. The second day I started to have issues again, so I disconnected the batteries for about 30 minutes and reinstalled the Hypertech programmer. Again, I had a great transmission for a day or so. Now, I have the intermittent, shuttle shifting, or whatever you want to call it. It does not seem to be caused by transmission heat, time of day, time of operation, or anything else. Rather, my transmission woes seem to be luck of the draw.

However, I have been fortunate enough in the time experiencing this to verify that the issue is as follows:
1. The truck starts of in 1st gear and shifts without problem;
2. The truck starts off in 3rd gear and doesn’t shift until TQ lock-up or 4th gear;

I have noticed, that the when I am fighting these transmission woes, the transmission stays in 3rd gear even when stopping at a light or sign, almost like the TQ doesn't release. Sometimes the transmission will go into 1st gear if I manually shift it down to first though (or it will stay in 3rd gear even when shifted into 1st).

Any ideas on the cause of the problem? Will the GM governor solenoid conversion fix it? Should I get a shift enhancer?

Your advice and input is really wanted and appreciated.

Hypertech

When you connected the Hypertech programmer, the first function it preforms is a DTC code check with the ECM. (unless it's a very old unit)
Did you get any DTC codes that may give a clue ?

Topnos

No, no codes present when going back to stock or when programming to-performance mode.