6L80 help needed!!!!

[Dee Eastwood]

I have a 2013 GMC Yukon XL 1500 SLT with 6L80 transmission and 203,000+ miles. The problem I’m having, when I first start the truck and drive it, it drives and shifts fine until the transmission reaches 180°-190° at this point if I come to a complete stop and then press on the gas it won’t drive. But, when I turn it off and them on again it will shift right into drive and/or reverse with no problem. Once I brake and come to a complete stop and press the gas, there’s no movement,  it doesn’t drive until I turn the truck off and then on again. I also hear a whinning noise coming from the transmission sometimes when it's started and soetimes when shifting into 2nd (the sound is similar to the noise that comes from the PS when the fluid is low... but the noise isn't coming from my PS). I want to get a idea of what the problem may be before I drive into a transmission shop and they overcharged me for something that’s not the problem. 

[newdude]

17 minutes ago, Dee Eastwood said:

I have a 2013 GMC Yukon XL 1500 SLT with 6L80 transmission and 203,000+ miles. The problem I’m having, when I first start the truck and drive it, it drives and shifts fine until the transmission reaches 180°-190° at this point if I come to a complete stop and then press on the gas it won’t drive. But, when I turn it off and them on again it will shift right into drive and/or reverse with no problem. Once I brake and come to a complete stop and press the gas, there’s no movement,  it doesn’t drive until I turn the truck off and then on again. I also hear a whinning noise coming from the transmission sometimes when it's started and soetimes when shifting into 2nd (the sound is similar to the noise that comes from the PS when the fluid is low... but the noise isn't coming from my PS). I want to get a idea of what the problem may be before I drive into a transmission shop and they overcharged me for something that’s not the problem. 

 

 

 

Sounds like the fluid pump is gone.  Once it warms up its losing pressure and not maintaining it.  

 

Time for a rebuild or replacement unit.  

Edited December 6, 2024 by newdude

[mjm-1957]

The filter is full of metal from the torque converter and blocking the flow of oil to the pump. That trans is done.When you shut off the engine the metal falls back in the pan and the whole process starts again when you try and drive it.The whining is the pump starving for fluid and probably destroying itself.

[swathdiver]

You got your answer from Nick on the other forum.  Sure, my assessment might be the exact cause but unless you do it yourself, no transmission shop is going to make a partial repair.