4L80E flush

[moose1]

I have read some of the talk about changing the tranny fluid and flushing all the oil out by disconnecting the cooler lines. I called our local dealer and he said not to do this because it will dammage the tranny because parts are still moving. He also said that because I have about 110 miles on it that flushing is not a good idea. Any thoughts would be appreciated.

95 td ext cab 4x4

[Spindrift]

I've just finished with this whole business. Lots of different opinions on this one. I'm changing over from dino oil to a synthetic and since I know my tranny had regular service (85K), I'm not too concerned about the flush, followed by the exchange. I've heard that if you haven't serviced a high mileage tranny, or you've bought it used and don't have the service records, you might want to think twice about a flush. You can still go ahead with the exchange. I also learned that a lot of service centers didn't differentiate between a "flush" and an "exchange". The flush is a chemical cleaning of the tranny before the new tranny fluid is added, or before the exchange...if you're going over to a synthetic.

[richard7]

Replacing the old oil in the converter by disconnecting the cooler lines will not damaged the transmission. Leaving the old oil will.

You have to understand that when doing it, it only stop the lubricating oil to the rest of the transmission for about 15 seconds. But the transmission doesn't work or turn the wheels! So no damage can occur.

I did this procedure probably over 100 times. I never had a problem and I never heard a problem with this because you can't! I have only heard dealers and manufacturers saying to not do it (because they often prefer you to keep the old oil in to sell you parts and service).
It is well known in the towing industy that you can't tow a rear drive vehicule without disconnecting the driveshaft. This is because the automatic transmission is turning but not the pump to insure lubrication. But the fact is that they do it if it is only for a short distance because is is not enough to damage it. there is some oil remaining to protect. This is much more hard then the 15 second of missing oil to non-turning transmission components!

To protect your transmission, I suggest that you put an auxilary filter kit in the cooler line; and don't be afraid to change your oil, leaving the old oil in will break your transmission. If it breaks soon after you change it, it would have break with the old oil too, because the damage was already there!

[moedog]

I HAD MINE POWER FLUSHED AT 50,000 AND CHANGED TO MOBIL 1 SYN. WITH NO PROBLEMS, HOWEVER NEXT TIME ITS DUE, I WILL DROP THE PAN AND REPLACE THE FILTER, THAT IS THE DRAW BACK OF FLUSHING, YOU DONT GET A NEW FILTER. IF I DIDNT KNOW THE TRANNY HISTORY I WOULD DROP THE PAN AND GET A NEW FILTER AT THE MINIMUM.

[moose1]

Thanks guys. I think I have my terminology mixed up. I am changing the oil and filter, not flushing it (whatever that means). Richard7 the dealer said that disconnecting the oil lines would cause junk to be sent thoughout the system and dammage the tranny. ??? Thanks.

[1995 6.5 TD 2500 4x4 ext cab 4:11 4L80E]

[GARY PAGE]

I have heard the same information regurading flushing the tranny after 50K miles. To that I say if it's got crap in it get it out and let's see what happens. If it's going to fail let's get on with it...my 02...

[eracers999]

Im with Gary on this one. If flushing is avoided then all your doing is leaving crap in there to help seal up a problem. If the tranny is still good then flush it. You wouldent just change 1/2 of your engine oil would you. If the oil isnt clean then i would get it out of there.
Kent

[moose1]

Tranny fluid never changed, checked with dealer from previous owner.

I did it! I put a 3/8 tube on the top tranny cooler line, ran it to the bucket,turned on the truck, ran it till it burped, dropped the pan, replaced the filter, put in 4 liters at a time and turned on the truck and pumped out old oil till it ran clean, added a tranny additive and it was done. Thanks for the info. The Page Rocks.


95 td ext cab K2500 4:10 180,000 km

[tanker]

Well I must chime in here as well. :D I have drained mine, changed the filter, then disconnected the cooler line, and added new fluid, while pumping out the old, almost each year since 1995, on mine. Same transmission (2nd engine :mad: ) and almost 150,000 miles with a lot towing in the summer heat, crosssed the country coast to coast 4 times, Canada to Florida, and it still works, shifts fine. And mine is toting over 18,000lbs when towing. ;) So if this was a problem with lack of lubrication, I should have been to "Aamco's" transmission shop a few times already. I can see if you would run it dry for some amount of time, that could doo some damage, but adding as it pumps out carefully should not hurt anything. smile.gif

[Scooby]

Ive used the 'pump out method' too , with no problems. Just change the oil and filter as you normally would, fill it up, remove the return line from the cooler back to the tranny, start er up, and watch the fluid pumping out. I dont let it run too long, and I stop and add more fluid. Once the fluid coming out looks clean, I hook the line back up, fill the tranny up, and its good to go. I dont let the pump 'run dry' while doing it. I just did my wife's Grand Prix, when switching to Amsoil, and I think I used 10 quarts. I may have pumped out more than necessary, but I was trying to get a good flush. Thats my .02