Transmission Fluid after 90k+miles w/o flush

[RAWVORTEC]

So I got the tahoe from my dad in 2008 and it had 170k on it. It's now at 266k. I have never touched the transmission because, honestly, i never thought about it. It's been super smooth for such a long time, but now, it just feels off. I want to get under there and change the fluid. What is the best way to go about doing this? This is a 99 5.7 4l60e

 

[laredo1307]

Do you know the last time it was changed? At 266k I would really leary of changing all the fluid. Definitely DO NOT take it somewhere and let them do a transmission flush. This could be catastrophic. If anything I would drop the pan, replace the filter, add enough new fluid to replace what came out, and keep on truckin. You've managed to make it past the average life span on these trannies so just take what you can get and save for a rebuild down the road.

 

[ScubaJim]

Do you know the last time it was changed? At 266k I would really leary of changing all the fluid. Definitely DO NOT take it somewhere and let them do a transmission flush. This could be catastrophic. If anything I would drop the pan, replace the filter, add enough new fluid to replace what came out, and keep on truckin. You've managed to make it past the average life span on these trannies so just take what you can get and save for a rebuild down the road.

I have even heard some horror stories about changing the filter. You may want to consider taking the pan down inspect and then just refill. Just my 2 cents.

 

[ccapehartusarmyINF.(ret)]

what do you mean by off is it slipping i mean with that many miles the clutchpacks are probably about done at 266k miles id bite the bullet and rebuild it
probably changing the fluid will make what ever yer noticing worse

 

[mcm1209]

I have 243k on mine and just bought it a month ago. No idea when the fluid was changed last.
Fluid is dark but not crazy dark. She shifts fine so I'm not going to touch it. Just make sure she is full and drive it until it brakes
Its what I'm planning to do. I do take it easy though

 

[laredo1307]

I was around 180k when mine start acting up. I kept checking the fluid and getting high readings. I bought an extractor pump and remove enough to bring it down to normal and sure enough it bit the bullet 2days later.

 

[RAWVORTEC]

Haha sounds scary. I may just leave it. And if I ever downshift into 1st, it'll almost not catch that gear. It wont automatically catch at least. Kinda skips a little. So when it does break. What should I add to the transmission to make this thing shift better and perform better