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OT Automatic transmission fluid

B

Bart CA

Member
Once oil is in the torque converter does it stays there
or it is exchanging/circulating in transmission while driving.

The dealers offer transmission flush or oil and filter change.

How many oil is required to flush the transmission to the
point that all oil is changed and transmission cleaned.

I am efraid that some used oil is returned in transmission in this process.

Just curious...anayway I always changed oil and filter I don't trust the
flush process.

Thank you in advance

Bart
 
The oil constantly circulates through the system.

Flushing is somewhat of a gimmick, it takes a lot of fluid to totally flush one.

If the fluid is dark and burned, the damage is already done. New fluid and filter may postpone the inevitable, but the reason the fluid is dark is because the clutches are failing.

If the fluid is still clean, no need to flush, just change the filter, replace what fluid came out, good to go.
 
I don't think there is anyway to get fluid from the converter to the transmisison. they are not connected and the converter on cars and light trucks don't swim in fluid either. even if they did there would be no way to ensure the right amount of fluid.

I think some converters have a drain/fill plug but most modern ones are throw a way.
 
i am not an automatic trans. specialist . but the oil does not stay in the converter. plus when engine is stopped converter is not full till engine is started.it all circulates around through the pump, converter, cooler, and valves and gears. if it stayed in the converter the converter would burn up. just like sitting at a stop light with your foot on the brake the converter is producing heat and more so with more engine rpm. early converters did have a drain plug but not nowadays.
 
I can't say about other brands but Fords had drain plugs in the converters. The couple I've done had two, 180 deg. apart. Take the lower cover off the bell housing and roll it around and drain one side then the other. The plugs were not near the edge of the converter housing so some still stayed in.
 
Fluid gets into the torque converter because it's pumped there. And it doesn't stay there because fresh fluid is always being pumped into the converter and displacing the fluid that's already there.

My opinion on flushes is that they wouldn't be very profitable if they used enough new fluid to flush out all the old fluid. But they certainly displace more fluid than a simple fluid change will. It's certainly unrealistic to think all the old fluid gets flushed out, which is not to say a flush isn't worth the cost. I've never paid for a flush but maybe I should have.
 
Depends on the vehicle, some cannot or should not be flushed as in some Hondas and Toyotas. Most GM cars flush out nicely, fluid travels all around, it does not remain in the converter. I typically run 12 qts through in a flush, and there is not really a good way to determine how complete the exchange is. Going by color alone, if the fluid is terribly dirty and black, almost no amount of fluid flushed through will stay clean looking. Flushing is maintenance only, if done regularly from new the fluid should stay bright and clean.
 
Why couldn't a bypass toilet paper filter similar to the ones used on engines be used to keep the fluid clean in the transmission? They keep the oil clean on engines when they are used.
 
They do have filters under the valve body in the pan. My duramax Allison has a spin on filter. Plus 1000 times better than that T. Paper set up that was used 70 years ago.
 
When I got my Duramax/ Allison, I undid the line going from the tranny to the oil cooler, ( cant remember now how I was able to tell which was the pressure and which was the return) slipped a hose over the fitting and ran it to a 5 quart oil bottle placed by the drivers' door, that I had placed a mark at the 2 quart level. I then started the truck, ran it till it reached the mark, shut it off, added tw0 quarts of tran fluid, emptied the old oil, and did it again and again until I had run through 16 quarts. I believe that I got about 90 percent exchange. I will do it again every 60,000 miles.
 
FYI, 2011 silverado the exhaust crosses over right under the rear portion of the pan and its pretty tight. The exhaust doesn't need to be removed but loosened at the manifolds and lowered slightly.

Dropping the pan on this truck you will use about 6qts
Fluid exchange machine is going to use about 16qts.
 
The above post was meant for other thread, but it's still related I guess. All fluid in the trans circulates when the engine is running. A fluid exchange machine does not allow old fluid back into the trans, but there is a going to be some mixing inside the trans while the process is going. This is probably why most machines hold a high capacity of fluid (i.e. 16qts). Would you want to replace only 5-6qts, and still have half or more of old fluid?
 
> Why couldn't a bypass toilet paper filter similar to the ones used on engines be used to keep the fluid clean in the transmission? They keep the oil clean on engines when they are used.

Transmission fluid doesn't get that dirty, and the big chunks of metal from wear are adequately captured by the transmission filter. The larger issue is that the fluid breaks down over time due to heat; no amount of filtering can prevent that.
 
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