DIY ATF exchange?

[Paul]

How bad of an idea is it to attempt a fluid exchange by yourself? I'm talking about hooking up a reservoir of 16 quarts Mercon V to the tranny cooler return line, and a catch tank for old fluid to the tranny cooler out line, then letting the tranny pump at idle do the work. Same method as used by dealers, sans the expensive machine. Can it be done? Tips? Thanks in advance for your advice.

[finster101]

I don't think the reservoir tank will work. While the pump pushes the fluid through the cooler it picks up from the pan. The machines you refer to have a pump to replace the fluid being pulled out. You can do this by having a catch can with a hose from your cooler running into it. Have the replacement fluid ready (all caps removed) start the car and begin pouring the fluid down a funnel into the trans pan. Watch your catch can and you can guage how much you have pumped out. when you get near even, turn off the car re-attach your cooler lines check and adjust the trans fluid level as needed. We did this before we had the machines.

[Paul]

Thanks for the info!

[BAD MERC]

You are one of a few that do that! I did it about every 30K on my 1995 Taurus (AX4N), got 172,000 miles out of the tranny. The ONLY reason it failed - the 1 - 2 shift accumulator spring broke and slammed second gear on the upshifts. Probably could have gotten 200K out of it otherwise.
I don't think the reservoir tank will work. While the pump pushes the fluid through the cooler it picks up from the pan. The machines you refer to have a pump to replace the fluid being pulled out. You can do this by having a catch can with a hose from your cooler running into it. Have the replacement fluid ready (all caps removed) start the car and begin pouring the fluid down a funnel into the trans pan. Watch your catch can and you can guage how much you have pumped out. when you get near even, turn off the car re-attach your cooler lines check and adjust the trans fluid level as needed. We did this before we had the machines.