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Dexron VI or III

No. Too thin and doesn't live up to the better heat blah blah blah ... Wiped enough of it off the rear tailgate after transmissions in other things smoked off.
 
Whoa there hoss. Why are you flushing?
when a transmission dies and you rebuild/ replace it- flush lines and cooler.
Only time to flush a transmission is you know you are replacing it but HOPE to squeeze another 5,000 miles from it- maybe.
otherwise you don’t flush.
 
All this tranny talk lately has given me thoughts of doing a filter service to mine. Fluid is clean but I don’t know how many miles ago if it was ever changed! No known issues other than I think my TCC lockup might be weak plus I’d like to install a drain plug on the pan like the newer ones have.
 
Will L. said:
Whoa there hoss. Why are you flushing?
when a transmission dies and you rebuild/ replace it- flush lines and cooler.
Only time to flush a transmission is you know you are replacing it but HOPE to squeeze another 5,000 miles from it- maybe.
otherwise you don’t flush.
Click to expand...

Huh? I’ve twice flushed the trans on my wife’s 4Runner. I pull the return line from the cooler to the trans and place in a bucket. Start vehicle, dump 2 quarts, shut off, add 2 quarts, repeat until fluid is clear. Simple pan drain and filter change gets about 3 to 4 quarts, leaving another 9 quarts of dirty used fluid in the trans.
 
Big T said:
Huh? I’ve twice flushed the trans on my wife’s 4Runner. I pull the return line from the cooler to the trans and place in a bucket. Start vehicle, dump 2 quarts, shut off, add 2 quarts, repeat until fluid is clear. Simple pan drain and filter change gets about 3 to 4 quarts, leaving another 9 quarts of dirty used fluid in the trans.
Click to expand...

Will L. must be confusing a power flush where they use a machine to flush the transmission. Reportedly these will push around built up sediments in the transmission, causing them to fail shortly afterwards. I’ve seen guys making claims on the internet that the sediment is what holds the transmission together, so don’t disturb it. LOL

What I’m describing is using the transmission’s own pump to push fluid out, this after doing a pan clean and filter replacement. This does nothing more than what the transmission already does on its own.
 
@Big T I like your idea on that type of flush. It gets all the old fluid out that has degraded over time with fresh fluid in

I would like to hear what others think that know tranny’s. I may do this myself if it’s a good route
 
dbrannon79 said:
@Big T I like your idea on that type of flush. It gets all the old fluid out that has degraded over time with fresh fluid in

I would like to hear what others think that know tranny’s. I may do this myself if it’s a good route
Click to expand...

Well I know it’s been described here before. Also elsewhere. I’ve down two flushes on the 4Runner which supposedly has lifetime fluid. It has 270K trouble free miles on it.

Although not the original owner, I believe this is the original transmission in the ‘99 Burb which has 232k miles. I typically drop the pan and change the filter every 30K miles. It does have a deeper, cast aluminum pan with cooling fins and I have a trans temp sender in the drain plug.
 
I’m curious if the tranny will suck it’s own fluid lol. Like if we were to disconnect the cooler hose in front underneath stick the suction end in a bucket of clean fluid and the other in an empty bucket. After a filter change and refill of corse. Crank her up and let the tranny cycle the fluid
 
4l80 completely different than a Yota.
The clutch composition in 4l80e does not do well with too much new detergent in it once you have high mileage on it. If you do the service every 30,000 miles - then flushing out the lines and cooler wont hurt. But flushing out the trans itself often becomes failure.

In the fleet with hundreds of 4l80e we just ran it and never did filter even unless it was often towing a descent load. These pickups were usually driven hard, but not loaded heavy. And by driven hard- I mean wot from every stop until 10mph over speed limit.

And just for flashback fun:

To Flush or Not, 4L80E

What's involved in flushing the transmission? Is it really all that it's cracked up to be, or is it just a way for shops to get your $$$. How much does it cost on the 4L80E? How often should it be done?
www.thetruckstop.us
 
Dex/merc fluid only unless you want to deal with leaks and a possible rebuild in 6-12 months. GM says it's backwards compatible because the patent on dex3 expired, so they recommend there new fluid, and if your trans fails in 6+ months they get you for a replacement.
 
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