Truck: '97 Jimmy 4.3 2-door auto 4x4.

Trans: stock 4L60E with fresh fluid & filter, correct levels.

What it's doing:

When first started up, the truck acts normal. Park/Reverse/N/D all act normal. Truck starts in 1st gear, and upshifts twice normally to 3rd. Then it's stuck. It will not upshift into 4th, and it will not downshift out of 3rd if I slow down. This throws a fault code that is picked up by a scan tool that the trans fails to downshift. When I take off from a dead stop from then on, the truck starts in 3rd. I can manually downshift the trans and it will go into 2nd fine.

The only way for me to "clear" this is for the truck to sit when parked for awhile, and then it will start in 1st again like normal.. but once it gets into 3rd it just stays in 3rd.

Any ideas?

This is the 2nd trans I put in the truck, so I'm really not looking forward to rolling the dice on another junkyard unit, so I'm hoping maybe there's a simpler fix... shift solenoids, etc. ??

 

Sounds to me like the trans is going into sluggish mode i call it can't remember the pro term, but my best guess is one of the shift solenoids is either gone bad or broken. they are located next to the filter when you drop the pan. The 2-3 shift can be broken very easily if its not in the right position when someone puts the filter in. happen to me once a while ago.

 

Yeah, I need to take a morning off work and take it in to the trans shop near my house.

I had read online that these 4L60E's default to 3rd in fault mode, but given that this always starts in 1st, I'm hoping that it's a solenoid issue or something.

Automatic trans are something I have very little knowledge of. All my other cars, and my preference, is to have a manual trans. I guess I need to do some more homework.

 

Not sure if it's something I caused...

but the trans shop said the 3-2 shift solenoid was bad. They replaced that and it's good to go! Woohoo!

 

Glad to hear everything worked out for ya. thanks for the update
have fun!