Replacing transmission fluid

[joegr]

A fluid exchange adds no stress to a transmission. The machine has a big cylinder with a moving disc in it. On the right side of the disc is fresh transmission fluid. The transmission pumps old fluid (from the cooler line) into the left side of the cylinder. This moves the disc and forces new fluid into the cooler return line.

To the transmission this is no different than normal running, except that old fluid gets exchanged with new fluid. I've never understood to thought of replacing only 20 to 30% of the fluid at a time. Imagine if oil changes were done that way.

 

[JoshMcMadMac]

With the lines, cooler, and TC; your lucky, like I said, to get 30% of it out..

Not looking for an argument, just trying to prove points to my theory..

Good thing, because that is an argument you would lose. I can get 7-8 quarts out when I drop the pan, which is half. I will also reiterate the need to replace the filter, which cannot be done without dropping the pan anyway.

A fluid exchange adds no stress to a transmission. The machine has a big cylinder with a moving disc in it. On the right side of the disc is fresh transmission fluid. The transmission pumps old fluid (from the cooler line) into the left side of the cylinder. This moves the disc and forces new fluid into the cooler return line.

To the transmission this is no different than normal running, except that old fluid gets exchanged with new fluid. I've never understood to thought of replacing only 20 to 30% of the fluid at a time. Imagine if oil changes were done that way.

I disagree, as this is not how the transmission is designed to run. If you did this while the transmission were operating, that would be different. Using a machine forces fluid past stationary parts that should be moving, and if not operated properly easily overworks the transmission.

As for oil, it does not have a 50k+ drain interval, nor a 15 quart capacity.

 

[joegr]

...I disagree, as this is not how the transmission is designed to run. If you did this while the transmission were operating, that would be different. Using a machine forces fluid past stationary parts that should be moving, and if not operated properly easily overworks the transmission...

Clearly, you must have seen different machines from the one I am. I am talking about the engine running and the transmission's pump pumping the fluid. There's no pump on the exchange machine I speak of.

However, it's clear that you are set in your way and that's that.

 

[oddball]

I think Josh is talking about the flushes where they use a high pressure pulsating machine to force fluid through the system. Agreed that seems a little nutty unless you have a specific issue like a known clog. Some theorize that the pulses can push a piece of debris out of a safe place and into a solenoid or clutch pack, causing failure.

This is also a theory that fresh fluid can shock a tranny and cause failure. Seems like a stretch to me.

As always, more opinions than fact all around. In general, keep the fluid fresh, replace as much as reasonable, use the correct fluid.

As a point of interest, I did a full flush (disconnected cooler return, hand-pumped new fluid) on the LS since it had been 150k miles. My other vehicles (00 altima, 06 sienna, 72 cutlass) I've always just drained the pan. The LS gets preferential treatment.

 

[Right on the Mark]

I myself will never pay for or have a flush done on my cars. Now thats MY cars everone else is different. I do the pan drop, clean,filter if the converter has a drain plug that gets emptied. I think of LS peeps as alittle more hands off in doing car work. More of suit and tie guys so suck and fill great for them. I don't think of LS owners as a 1980 clapped out Tempo driver that does not have 2 nickels to rub together.

 

[JoshMcMadMac]

Clearly, you must have seen different machines from the one I am. I am talking about the engine running and the transmission's pump pumping the fluid. There's no pump on the exchange machine I speak of.

However, it's clear that you are set in your way and that's that.

As oddball pointed out, the machine you speak of sounds much better than what is typically used for a transmission flush. No need for condescension...the process you are describing actually sounds great, like a blood transfusion.

I think Josh is talking about the flushes where they use a high pressure pulsating machine to force fluid through the system. Agreed that seems a little nutty unless you have a specific issue like a known clog. Some theorize that the pulses can push a piece of debris out of a safe place and into a solenoid or clutch pack, causing failure.

This is also a theory that fresh fluid can shock a tranny and cause failure. Seems like a stretch to me.

Thanks for the added clarification, oddball, that is more what I am familiar with. I also agree that clean fluid alone is highly unlikely to instigate failure.