rustypigeon

I know a lot of people here disconnect the cooler lines to flush the transmisson. I am just wondering where the return line goes. I am wondering if the return line serves as a lubrication function to something. Is it likely to damage something if I disconnect the lines to give the tranny a good flush? In the past I have just drained the pan in frequent (15k) intervals and my fluid always stays bright red.

It is a '94 Pickup with an A340F transmission by the way.

ayev8r

If the fluid is always red,and you change it often...leave it alone. Most times people flush, is because they never change the fluid, and it gets a build up everywhere. Dealers think its a good idea....but only if they do it. Dealers stealers.

mattaway

i'd stick with the ol' drain and fill method myself, but if you're going to have it flushed, make sure the flush machine operates off the the tranny, and isn't a "force-flusher" most flush machines force the old fluid out, and force new fluid in, which can cause more harm than good.

JDMSLIK

I used to work at this tranny shop before I started my apprenticeship. The place was harsh old school. Was owned by this cheap italian who'd been running it for about 40 years. Before I tell you how we used to flush em I gotta say this guy had an impeccable record and was considered second to none when it came to customer service. Highly recommend going to him if your in the vancouver bc area. He's good and he tries to save his clients money.

First we drop the pan and filter, replace the filter and put the pan back on. Then we'd hook the cooler lines up to the flush machine. It's been awhile so bare with me. I can't remember what the term or the machine was but it would just circulate smoking hot atf through the cooler. We'd let it sit on there for about an hour, cleaning out the coooler. Then we'd put longer extension hoses on the cooler lines to the transmission. One of the hoses (the one that pumps the fluid)would be in an empty 5 gallon bucket. The other hose (the one that sucks the fluid) would go into a bucket with about 20 litres of fresh atf. Then you start it up in park. When the one bucket is full and the other empty shut off the vehicle. Re-attach the cooler lines and check your level.
Problem with flushing AT's is the only way to change 100% of the fluid is to drop the transmission and replace the torque converter.
The reason I like this method is you don't really need an expensive machine to do it. Unless you want to clean out your cooler.

Jay351

Thats exactly how my old school mechanic tought me to flush automatics.. He said its the least harmfull and overall best way to flush a tranny.

rustypigeon

I am just wondering if the return line going back into the tranny serves any lubrication function, or does it just empty into the pan. If it just dumps into the pan, I may flush. I just don't want to damage anything if the return line is serving some other purpose.

The return line in my tranny looks to high up in the case to be just dumping into the pan. It almost looks like it is going somewhere... like to a clutch pack or something.