4l80 no 4th for about 10 minutes
 

So I have a 1997 K2500 burb with a couple month old 6.0 swap. It has the 97 4l80 with an transgo HD2 kit (about 50K on the shift kit). Last weekend I installed a used converter I got from a friend. It's a sonnex tripple disk billet converter he used in his truck. I wanted to change converters becasue I wanted a little higher stall than stock, and a month ago I was getting hard 1-2 trans shift issues after driving on the highway for over 15 minutes. Through research and other people with that issue, they said it was their stock converter starting to fail at lockup on the highway. the past couple weeks the trans has been fine though. But last weekend I installed this converter and also replaced the Lube Regulated Pressure Regulator Valve with the Sonnex one with the hole in it, since i have heard that this needs to be replaced when adding a tripple disk or you can stall when selecting gear. SO I did this, did a fluid/filter change, and it was fine for the first day. Then I noticed going to work the next morning it felt like it wasnt going into 4th. And if I stayed in the throttle the converter would seem to lock, but now im locked in 3rd not 4th. the strange part is with HP tuners the ECU is saying that i am in 4th when I am obviously not. however after about 8-10 minutes of driving it will then go into 4th. And once it finally goes into 4th, it will shift just fine the rest of my commute stop and go and highway. Untill I turn the truck off and go drive again. When It is stuck in 3rd I have played with the shift selector and nothing happens. I am going to swap back to the other valve this weekend to see if that fixes it. Anyone have any insight on this issue or ideas?

When you are in 3rd on the freeway and give it more gas do the rpms just rise?

they dont rise if I give it some gas, because i believe my converter is locked. unless i give it more then it shifts to third and unlocks, although its already in 3rd.

the hard 1-2 shift usually comes after a transmission component slipping code. have you set any codes? i believe its p1870 code

I never set off any codes. I believe you were the one to answer my other post a few weeks back... https://www.performancetrucks.net/fo...riving-549562/

i would have someone more knowledgeable look at it. Mine ended up costing me the converter and the trans. it took about ia year but it finally shit the bed.

I changed put that valve from the sonnex one with the hole to the old solid one. Truck doesn't stall when going into gear which is good. However I am still not getting 4th gear. All other gears shift fine. The converter locks fine. And the Ecu thinks that it is in 4th. Idk where to go from here besides some trans shop. I really don't want to have to rebuild a trans right now.

I had one do this a long time ago (4l60 tho) it ended up being a slipped O-ring on the servo. Not sure if this applies to the 4l80 and I'm not a trans builder but it's worth a look right?

I dont believe the 80 has servos like the 60.

I trying everything I can before having to drop this trans, so I installed a remaned valve body. Took it out for a spin and it's doing the same thing, and if anything now 4th comes in even later (have to drive more). It didnt come in until the trans was almost at 150 degrees. The trans used to shift into 4th about 10 minutes into my drive to work. Now it didnt shift into 4th at all today on the 20 minute commute. is it possible this is some sort of electrical issue? I dont think so though because if it was a solenoid then I wouldn't have 1st gear either.