So the wifes yukon is the 2500 chassis and has the 8.1L with the 4L80e trans, it is upshifting WAY too early and when i put my foot in the throttle after it will not down shift to speed up. Ill take off from a stop and it starts in first then almost soon as im rolling goes to second then seems by the time were at 35 its in overdrive, as mentioned i can mat the throttle and just lugs its way up to speed. My liuck has been super shitty lately .

I drove it the whole weekend with no issues and parked it, i believe the same day or day right after i cant remember as my shift has my days all jacked i went to drive it down the road and this started. It just throws me off that it ran fine all weekend parked it and then now this the very next drive.

Anyway is this a TCM issue, valve body issue, converter, or what? I still have the truck to drive around and get to work and what not but just want this fixed so i have both vehicles back.

Any input is appreciated and thanks in advance.

 

Sounds like VSS issue..is it 4wd?
my buddys truck did weird stuff like that and replaced the VSS and fixed it.

 

Yes sir its 4wd, it has said service 4wd for a few days now but i honestly didnt think that would have a direct relation to the trans.

School the noob on autos here whats VSS, if that even deals with the trans.

 

I would get it scanned and make sure to look at all the different modules. There has to be a code of some sort for this to happen. Keep in mind the trans is only going to shift when the TCM commands this and then the solenoids make it happen. This is not a trans related issue if I were a gambling man. You have as mentioned above a VSS issue, TPS or controller issue if I had to guess. Look into these things and I'd bet your going to find what you need to address. HTH Vince

 

Thanks for the input fellas ill give the ideas a look and i was laying down last night thinking about it and VSS is Vehicle Speed Sensor right haha and of course TPS Throttle Position Sensor.

I dont think its the TPs cause it will rev fione in neutral and park with no issues so i would assume it is working correctly. Also there arent any Lights on the dash coming on.

 

My truck is a 2000 Yukon xl2500 and it's doing the same things exactly that you are describing I would love to know what it is for sure

 

The OP hasnt logged on since 2015 so im not sure he is going to see this.