2017 GMC Sierra 6L80 Transmission Fluid Change Advice

[Hexa Fox]

Hey guys, 

 

I recently posted about this but I think it was in another GM forum. I was specifically asking about troubleshooting my transmission then. To try and get right to the point, the transmission fluid in this truck has never been changed but the truck just passed 33,000 miles. In the past year or so I have been using the truck to tow some very light loads (probably around a ton with mower and trailer combined) and doing a lot more highway driving. I had started to experience what I thought was a slight slip in the transmission. I have already had a lot of recommendations and it seemed like a good choice at the moment was to replace the thermal bypass valve on the side of the transmission that the newer trucks have. It opens at 150 F instead of like 200 F. I have been trying to do some reading here but just figured I would come out and ask for some help.

 

My next step was to try to change the fluid as soon as possible to try and reduce the damage to the trans, increase the life of the trans and maybe even resolve or reduce the shifting I am experiencing. So today I was just taking a quick trip to town and while going up a slight incline the truck experienced a horrible shudder. It felt like it was taking time to find the gear and quite honestly it felt like it may stall the entire truck or something. To be entirely honest, I'm not even certain it was the transmission I just believe it was. 

 

Before this gets out of control, I guess what I am looking for right now is advice on the best route to change the fluid and any advice you guys may have. Also I have not driven the truck like a maniac or mistreated it either. Maybe I should have changed the fluid earlier but with 33,000 miles on it I thought I would have a little more time. Anyway I have changed the fluid in a 6L80 before but that was before they added the thermal bypass valve. In the past I ended up taking off one of the radiator lines and letting the pump help me get a lot of the fluid out. I have seen people still do it this way. As in they wait for the thermal bypass to open and add fluid and try to get out as much as possible but I'm not sure how dangerous that is or if there is just an easier way. I'm also aware of the exhaust blocking the pan, I know there are some tricks to getting it off, been there done that. I was hoping to get as much fluid out as possible.

 

I will leave this as is for now but any advice or feedback would be greatly appreciated. I kind of had half a plan to get a couple quarts of Lubegard, use Valvoline Maxxlife ATF, change the filter and just hope for the best. 

[Racer311990]

I use a fluid extractor to suck the trans fluid out of the dipstick tube. If I jack the front up a few inches I can get about 5 to 6 quarts. I do this every 10k but I bought the truck with 65k and the fluid had never been changed.

That first time i dropped the pan and changed the filter but there is no reason to ever do that again if you keep new fluid in it