BIGMAC

I was at the track this past Saturday and made four strong runs on a newly built race-spec 6L80E. All shifts were good.

However, on the last run the transmission went into neutral on the return road. I lost reverse also. By shutting the car off and restarting it I was able to go forward or reverse for a short distance before going into neutral again. By repeated shutoff / restart I was able to limp the car back to the pits and onto the trailer. I scanned for transmission DTC’s and there were none.

Ideas on what is happening? Are there diagnostic/repair actions that can be done locally, or do I need to have transmission pulled and sent back to the remote builder?

Your reply will be appreciated as my 6L80E transmission nightmare continues!

da6speed

Not saying this is your issue but this same thing happened to me once in a truck I had with a high mileage 6L80. It would drive for a bit until it warmed up and then it would lose all gears, coast to a stop, shut it off, crank back up and it would have gears for a 100yds or so and then quit pulling again. I had a friend that was a GM tech stop by with a tech2 scanner and it showed zero codes or anything wrong. Result was the converter went out and filled pump up with trash, wound up putting a whole new transmission in it.

grinder11

A great argument for installing a new converter with a new trans. It sounds like you're correct on the OPs trouble. The pump pickup screen gets plugged, the pump cavitate's/starves for oil. When you shut it down, the junk blocking the pickup falls off the pickup, and goes to the bottom of the pan. When started, it starts sucking junk, but moves forward until it becomes blocked again.......