How to flush a transmission

[BlenderWizard]

Alright, when I get around to flushing my tranny, I think I'm gonna move it over to synthetic fluid. I am, however, wondering just what I need to do to flush my tranny properly to make the switch. I know the torque converter holds a lot of fluid, and dropping the pan simply won't have an effect on what is in there. I'm a pretty hardcore DIY guy, so "hit me with the 411" on how to drain and flush a tranny.

[rjirvine]

Not that this helps, but my local dealer charges $117 for a flush. I think I'm going to have them do it. I know there is a new Dextron IV out, I'm going to see if they will flush it with that.

[jethro_3]

I had my flush done as a full power flush, pan dropped lines hooked up and all fluid changed for $115 complete. Can't beat that to ensure all the fluid was pushed out.

[draboo]

I have never tried this. But someone told me they tried it and it worked.

find out which tranny line is which. The warmer of the two is the feed into the radiator and the cooler one is the return.

somehow securely connect some clear plastic hose to both return and feed lines,each long enough to reach in front of your truck and insert each end into a 5 gallon plastic bucket.

Find out the fluid capacity of your transmission. Pour that amount into the return bucket.

Start truck. The feed line should be spitting fluid into the one bucket and the return line should be sucking it in at about the same rate. If the fluid coming out is visibly darker than the stuff going in,it will be easy to tell when its flushed out completly..the fluid will change to a brighter red coming out,easily noticeable in the clear hose.Plus,when your fluid is almost gone from the return bucket,its time to check the fluid level,I would think.

Again,I have never attempted this,I just take it in and have it changed myself,but it sure sounds like it would work.

Any comments yea or nea??

[MagicRat]

That post was mostly good, but usually the return line doesn't suck much. Instead, try doing a pan and filter change as you normally would. Then, before you start it, disconnect the line and put it in a bucket.
Then start the truck and pour new fluid in to the trans filler/dipstick pipe, until the fluid comes out the ine really clean.

[draboo]

Originally Posted by MagicRat

That post was mostly good, but usually the return line doesn't suck much. Instead, try doing a pan and filter change as you normally would. Then, before you start it, disconnect the line and put it in a bucket.
Then start the truck and pour new fluid in to the trans filler/dipstick pipe, until the fluid comes out the ine really clean.

Now THAT makes more sense. Now I think I understand why those machines the shops use have a pump in them with a pressure gauge. I noticed that they check the fluid level and adjust the pressure throughout the process.

edit: I think there isnt any return pressure. I believe its all pushed thru with the feed line,thru the radiator,then just "pushed" back to the tranny.

[internic]

i can see how the pump would more push than pull. anyone think it would work if you connected a hose to the (return-to-transmission) line, and elevated it a good 4 or 5 feet, and jammed a funnel in the hose, and dumped it in there at a rate to match the fluid coming out of the other line?

[BBKG]

Originally Posted by MagicRat

That post was mostly good, but usually the return line doesn't suck much. Instead, try doing a pan and filter change as you normally would. Then, before you start it, disconnect the line and put it in a bucket.
Then start the truck and pour new fluid in to the trans filler/dipstick pipe, until the fluid comes out the ine really clean.

I asked my dealer if they supply a new filter and he told me they flush the tranny through the filter? Is this correct? I'm assumin they're going to use the same filter when done. I'm bringing my own 16quarts of Royal Purple Max ATF, should I get a filter as well? If so, which one? Advance Auto Parts has Deep Pan filter kits and 16 & 17 hole kits???????

[horse482]

GM uses two different depths of tranny pans on the 4L60E, the filters are not interchangeable. One is 2 1/4 the other is 2 7/8 inches deep.

[EA6BMECH]

Well seeing I doubt your gonna tell a difference in the running of the tranny. I'd just change the fluid in the pan out, run it for a few days and do it again. You'll get enough fluid changed to justify it IMO. I would do that with my Camry. About every few oil changes, I'd pull the plug (thank you Toyota) and then stuff another 2.5 qts back in it. That way the tranny fluid stayed pretty fresh. Unless your hell bent on running synthetic, that's too much time and $$ to bring my car/truck in to have someone else do it.

[TwentyPints]

at what milage should you flush the tranny, as well as other fluids?