Change atf or not?

[diyer2]

Here I go again, I change fluids more often than the severe schedule. It has served me well, my 93 Silverado trans went 250k, my work truck, not easy duty. 

Then I switched to Amsoil OE products, worth the cost to me. 

[lizard-navy-keep]

late to this thread but yeah replace ATF.  you have nothing to lose.  

 

bought my truck with 5 miles and around 19k the 6l80 acting goofy.  called dealerships to utilize my precious warranty and got told transmission guys are backed up 6 weeks and i'd have to leave the truck and no loaner.  After losing my previous truck to the 6 speed rumble strips i started swapping out a gallon atf every 6 months and added the thermal bypass.  

[customboss]

Maybe use this ? First I’ve seen it offered. 
 

 

[Black02Silverado]

Keep changing it until it is a good red color. 

[diyer2]

I think you are starting this fluid change late, good luck.

[Black02Silverado]

4 hours ago, diyer2 said:

I think you are starting this fluid change late, good luck.

He might be, but I have seen good results from customers that started this late so there is hope.

[Atlas]

Why not drop the pan, change the filter, and do a couple of successive drain/refills while it's warm (thermostat open, if still equipped).

 

It's not that hard, or expensive, and accomplishes replacing 95% of the fluid at once.

 

 

It's like when people do this with power steering and use a little turkey baster to suck a little bit of fluid out and replace it with new over several oil changes. Jeebus... Pop the dang return line, hang it into a pan, plug the reservoir and have someone keep it full with new fluid while you crank the wheel lock to lock (with the engine off). It takes 10 minutes to do, and then you're done, completely flushed the system with clean fluid which should be good for another 20-30k before you should change it again. Hang a power steering filter on there for a gold star/ bonus points.

Edited November 28, 2025 by Atlas

[MikeBMW]

This may come back to haunt me, but I've had my truck in every 5000 miles for a drain and refill, with filter, on the transmission - never a transmission flush.
Along with the fix from Chevrolet TSB 21-NA-199.pdf, no issues with 98K so far.

Edited December 30, 2025 by MikeBMW