Transmission fluid flush and change advice

[GK813]

I'm going to change the transmission fluid in my VS Ute, I was going to put some clear hose down the pipe where the fluid level stick goes and suck out the fluid but I see I have a transmission radiator in front of the normal coolant radiator, should I remove the outlet of the radiator to suck out what is in the radiator or just use the fluid level stick location

 

[vs-lover]

There are multitude ways of doing this and it depends on what you want to replace and how much coin you want to spend.

Most times the job is done half arsed by just dropping the pan, replacing the filter and then just replacing the pan on and using a new gasket and then refill, which only fills the pan up again.

To me that's a half arsed job as the Torque Converter is still full off old black fluid that will just mix with your new fluid and start the degrading process again really quickly.

When I do a trans fluid change I will remove both the lines that go to the cooler / radiator and run one side into a bucket and the other suction line into the new trans fluid source.

Then start the car and watch it pump out the old while sucking in the new. This will happen really quickly so you have to watch it carefully and have two operators. Unfortunately to do this properly it will require around 10 litres of fluid to be used until it's totally clean, but this way the whole trans will have clean and new fluid throughout and not just a cocktail of old and new mixed together.

BTW Trans fluid is put out on special quite often and this is the time to buy it and do that job, not when it's at full price.

 

[woteva]

I always suck it out the dippy hole before dropping the pan as it reduces the risk of spillage.

 

[Skylarking]

When I do a trans fluid change I will remove both the lines that go to the cooler / radiator and run one side into a bucket and the other suction line into the new trans fluid source.

I thought the trans pump pushed the fluid out of the trans and through the cooler before going back into the trans. It can’t suck in new clean fluid, only blow out old crappy fluid

I thought that’s why many start their engines to push out the old fluid and then stop the engine when the trans fluid coming out starts to stutter. At that point, the pan is almost empty so it’s topped up via the trans via the filler tube (filler hole). Then the start/stop process is repeated about two or three more times... The second to last time you may want to drop the pan and change filter

(bit of a thread drift follows)

As the trans pump pushes fluid out, I’ve always thought a nice big 200mm clear pipe could be fashioned up with a floating piston separating two chambers. The dirty chamber would be empty with a floating piston separating it from the clean chamber. With the piston to one end so the dirty chamber has little volume, you could fill the clean chamber with 10 litres of nice new trans fluid. The you could connect the trans output line to the dirty side and the trans input line to the clean side of this flush tool.By starting the engine, the trans pump starts to push out the old fluid, which pushes on the floating piston, which pushes on the clean fluid forcing it into the trans...

Ideally the pipe should be clear so you can see what’s going on and the piston should have seals to stop old fluid getting past it into the new fluid but it doesn’t sound like rocket science to home fashion such. The tube material should be strong and dimensionally stable at +100C. But I haven’t found suitable clear 150-200mm pipe that can handle +100C without deforming which can be used as a basis of such a home made tool... Grey plastic sewer pipe could be used but with such you can’t see where the piston (which isn’t ideal). You could use grey pipe and dimension it so it can flush the average 6l80 clean and use a short clear input tube to the pipe... I’d think fashioning such is doable for the home handyman... just don’t blame me if the dimensions are wrong and the pipe bursts throwing fluid everywhere Hence a clear pipe makes it easy to see that you need to shut engine off before the piston gets to the end of the tube and it all goes boom... Such doesn’t resolve theneed to drop the pan to change the filter

Anyone make up such a home flush kit?

 

[vs-lover]

Yes you are spot on correct, it's been a while since I've done a full "SHAMPOO" as it used to be called.

The trans does actually pump it out and you have to manually stop and fill it up again, thus why you have to start and stop constantly once the pan has been drained.

Yes the last time I did one was around 2 years ago and I forgot about the manual filling, anyway thanks for pulling me up as it's reminded me again of the process.