Flushing Auto trans by pulling return line?
 

Hi all, i've been wondering if i could flush the transmission oil by pulling one of the oil return lines from the oil cooler? I've already dropped the pan and changed the filter, but i know i only got about half of the old, dirty fluid out.
I was thinking pulling the return line, put in it a oil container and let it run in nuetral until it runs out of fluid( or close to it). Shut it off, fill it back up and do this over until the fluid comes out clean. I've never done this before, so i don't know if it's a good idea or not and i don't want to mess anything up.
Any ideas?
Thanks
Brent

sounds risky but you might be ok if there's no load on it. The pumps need oil all the time.

Edwin

I've never tried it,but a friend of mine does it every time he services his trucks tranny. He says it does waste some fluid,but his has 300,000 miles on it with out a rebuild. His truck is a 1st gen. cummings with three speed auto. :)

It's a bit tricky, and you will waste some tranny fluid, but it's best to add fresh fluid as you're dumping the old (from the cooler line) into a 5 gallon pail. Get a funnel that flows well and just keep pouring fresh in untill it comes out bright red in the pail. Most better speed shops/parts stores will sell a pressurized can of flush that you can blow out the heat-exchanger in the radiator with. For that process you unhook both lines from the exchanger and just blow this stuff through. My buddy, who's a 20 year automatic tranny tech veteran, will not hook the cooler lines back to a fresh tranny w/out doing the exchanger flush.

Flushing it out thru the clooler line is the only way to get it all out! (out of the cooler, torkconverter and lines)........BUT if the fluid is black, (no red tint to it) I would pass on the flush cus the the truck may not move at all after your dunn!


IF IT BLACK, REBUILD IT, OR DRIVE IT TELL IT FAILS!!!!!

Yeah, i was thinking about dumping it in as it is draining out to keep oil in it. It isn't black or burnt. No chunks so it should be ok. It doesn't really even look too bad now, but i want to do a thorough job.
Brent

I did this on Dad's truck, it works great, just have one person running the ignition, and one watching the fluid because you don't want to run that baby out. Good luck

What Matt said. It's definitely a 2 persion job.

You don't have to turn the truck off to do this. Just put it in neutral to get fluid pumping then back into park to add fluid. One person can do it just making sure not to drain too much at one time. It is easier with two though.

Carl

I replaced my own fluid once on a Ford bronco. They even had a drain plug in the TC. NEVER AGAIN! The mess I made is still showing on the garage floor. You see Ford had a better idea. The Drain to the TC faces forward. When the fluid came out it hit the exhaust crossover and that acted like a yard sprinkler. You can guess the rest. 15 pounds of kitty litter later I had a dry floor. The large tote that I was using to catch the oil ws only dampened.
The next fluid change ws done at the service garage with a really neat system that ties into the cooling lines and uses the vehicles transmission pump to force the old fluid out and the new fluid in. Well worth the $80.00 spent and it took half as long. It will even tell you if the strainer needs changing. [coffee]