Joe's4l80e

First time here and looking for help thank for your thoughts, not sure where to post my question either

I have a 4l80e in my 2000 Sierra 2500 4x4
Third gear and forth gear don't shift until the rpm hit 4000 , the engine speeds too high and the speedometer hits 60km/hr before shifting into 3 and doesn't shift into top gear until it reaches 100km/hr. It's hard to tell if 1st and 2nd are working properly they appear to be.

Last year after a set of clutches burned up I decided to do the tear down and rebuild my self. I picked up a complete set of clutches, steel plates, seals and gaskets and new pressure switch and other solenoids

Took my time , cleaned it all up, put it together and after a little trouble shooting a broken wire to get the wire to the VSS resolved, I noticed the shifting was at a higher speed and RPM peeked at 4000 to shift gears . All and all it was running ok so I continued to drive it like that for a while and never got back to trouble shooting it. Now I just lost reverse gear when it was stuck in the snow jack-knifed with a trailor of plywood in the snow, My thought is the reverse got cooked or the servo piston pin is damaged. Now I got two things to fix while its out,

Any idea where to start trouble shooting as to the original shifting problems. I have been researching what makes the tranny shift and I'm still unclear about the process. The computer gathers it info from either or a combination of sensors VSS or TPS etc) and then would energize the solenoid to shift at some point,

mrvedit

You certainly are posting in the right place.
The shifting is completely controlled by the computer based on the TPS and VSS sensors and the tune in the PCM.
However Reverse is completely controller by the trans, nothing electrically is involved.

The loss of Reverse sounds like an internal problem which will require removing the trans. I assume the shifter reaches Reverse and that you have Park.

Later, after fixing the Reverse problem, if it still doesn't shift properly, connect a scanner which reads the commanded gear to confirm whether the problem is in the trans. Most often it is not.
Often late shifts are causing by a sensor problem, such as the TPS reading a much higher value than it should.

The trans also adjusts its line pressure according to the load on the engine which is determined by the PCM reading the MAF, MAP and TPS sensors.

Hopefully one of the 4L80E gurus can give you advice on the loss of Reverse.

Joe's4l80e

Thanks for the info mrvedit, hopefully I can get all back together again
Just finished removing the transfer case and tranny
The transmission fluid stunk burnt so that wasn't good. lots of black ugly oil. quite depressing actually for me as I was hoping for the best. It was almost gummy the oil
Yes to your assumption about my shifter reaching park and reverse. And I do believe that park was working before I tore it down
All my clutches looked new still but stunk from the dark tranny oil. and i was expecting to find the reverse band burnt but instead it was front band (the intermediate) that was fried down to the metal and the drum was scored badly (gauged up).
there was a snap ring was loose, dislodged and scuffed up too
Its mid night now so that as far a I got tonight
I got read up some more

any ideas what's going on, did this happen over time from a lack of clearance from the pin . or could of jack knifing a trailer getting stuck and rocking it cause it to go like that ?

Joe's4l80e

So .still at it and still need help
Considering the damage I had to the direct drum from the band being torn down to metal I decided to pick up a used tranny from kijiji and put it in
I was debating on opening it up before i put it and decided against it as i didn't want to risk it in case I screw up something. I regret it now

anyways but a second tranny in and still got no reverse. what the hell

could the used tranny have no reverse as well, what are the odds of that?? the guy said it worked fine when he pulled it

or is there something from the electrical end, the pcm or a transmission computer that can be causing the reverse from engaging the reverse gear.

I read on one sight that a safety feature could be locking out the reverse from working after I slammed the original trany in reverse from drive but I haven't been able to find out any more about it.

So while it was blocked up in the garage I unplugged the plugings to the tranny and drive still works but no reverse.

Took it for a ride and its a smoother shifting tranny than my original tranny but the rpms still seem to high before shifting gears
It shifts at 35 km/hr and then at 60 km/hr and again at 80 km/hr and I think - but not sure but again at 100km/hr.

at one time it would not go over 100km/hr and the rpm would not go over 2200 rpms as if it locked down with a governor ??? I'm thinking maybe the TPS sensor ?

any thoughts ,,, especially could a bad electrical connection stop reverse from working:ban

1984 elcamino

So I'm having shifting problem it will rub to 3000 RPM and then run through the gears but won't rev past 3000 RPM and in first and second gear it will rev out to 2700 rpm before shifting at any throttle position so it trys to break you neck on the shifts

So a little back ground information 6.0ls with a truck Norris cam makes 420hp to the wheels on motor, trans is a 4l80e built for 1000hp has always shifted great till a couple of days ago fluid is spotless I'm running a tci trans controller nothing has changed with the tune nothing is different it just outta the blue started shifting like garbage

So the interesting part when you let it sit you can drive it completely normally but the moment it's hot or you make a hard pull in it, it goes into a limp mode type thing like what I was describing above

I'm stumped please help