I had a new transmission installed several months ago. They said to change the fluid after the first 5000 miles. I'm almost there and deciding if I should do it myself or take it to a shop. I can change the fluid and filter but I'm wondering about the fluid that remains in the cooler, lines, and torque converter. I don't just want to do a drain and fill, I want all the fluid changed because it's the right way to do it. I also want to replace it with a high-quality fluid and not mix with the old. Is this something I can do in my driveway or does it need to go to a shop?

 

A drain and fill is all you need. Especially with only 5k on it. Dexron VI is high quality fluid.

 

X2 agree

 

X3. If you would like to go one step better install a drain plug and put some magnets in the pan when you have it off. Then it will be easier when you change it next time and the magnets help steel particles from getting stuck on the electronic solenoid valves.

 

Could also just drain/fill, run a bit, drain, repeat another time or two. That will keep mixing the old in with the new, dilute it until mostly new fluid. Might wait to change the filter until the last drain.

 

A fluid exchange basically involves disconnecting a cooler line so that you can inject new ATF while the old ATF pours out of the transmission. When I saw it done it was up to the operator to decide when to stop based on a certain amount of ATF that was sold or to stop when the fluid looked good visually as the exchange machine held quite a bit of new fluid.
I don't know about your transmission but mine has a drain plug. You would be better off to dump the pan once in a while and spend 100% of your money on fluid instead of paying for the service.

 

Not considering cost, is there a difference in quality between the brands of Dex VI? I'd like to use the highest quality possible, even if it costs a bit more.

 

This is a great idea

 

This is exactly what I did with my '04 Express 3500. I used the quick disconnect top ATF cooler line in the radiator, used a clear vinyl line that fit snug over the end and ran it into a 5 gallon bucket. Removed dipstick and inserted the largest funnel that would fit the dipstick hole. Had a helper start the engine and as the old ATF exited the vinyl line, I poured new into the funnel into the dipstick tube. Helper shifted through each gear (with emergency brake on) for about 10-15 seconds each gear while I was performing the fluid exchange. After a couple of gallons the color exiting satisfied me as clean and red. Stopped everything, reconnected, checked and corrected atf level, test drove, then check and corrected level again and checked for leaks. Easy process and low cost.