Looking to build transmission flush machine, have a few questions

[fallenauthority]

Well I am amidst a new brain scheme of mine. Building a Trans flush machine. I have the whole setup drawn up, but I cant figure out one thing. I am going to use a pump to pump new trans fluid into a trans line while the trans pumps old fluid out. I havent been able to find at what pressure a transmission pump operates at. I need to find out how strong of a pump I should use, I know it cant be too strong so I dont want to get a pump that can force fluid back into the trans at too high of a pressure. Any ideas?

 

[BrooklynBay]

Keep in mind that the transmission has a built in pump, and will add pressure to your pump. Keep the pressure low, and the volume high. You don't want to force fluid through it. The goal is to get the old fluid out while adding new fluid into it.

 

[fallenauthority]

Well the setup I had in mind was to have the outlet line from the internal trans pump run through a line into a tank in my machine. Then have a dedicated pump to push new trans fluid from a fresh tank into the return line into the trans.

 

[BrooklynBay]

Add a spin on filter onto your set up. You could use a filter that is used on oil tank systems if you want to have a reusable set up.

 

[MrShorty]

I need to find out how strong of a pump I should use, I know it cant be too strong so I dont want to get a pump that can force fluid back into the trans at too high of a pressure. Any ideas?

I don't think you need much pressure. I know when I was looking through the manuals for my A4LD, when you want to test transmission fluid flow, you disconnect one of the cooler lines, and extend it up to the dipstick tube and let it pump into the dipstick tube (and from there it simply drains into the pan). I haven't looked at the expensive machines, but my understanding is that most of them hook up to the cooler lines (and I'm assuming that is your plan here as well). Which suggests to me that your machine could do the equivalent of pumping the fluid back into the pan which isn't under pressure.

With that said, I think it would be more important to look at the pumps flow rate. I would even expect that the expensive machines have a feedback loop built in so that the machine can match the inlet flow rate to the outlet flow rate.

 

[BrooklynBay]

The Harbor Freight machine uses shop air to provide the necessary boost pressure: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93019
http://www.harborfreight.com/manuals/93000-93999/93019.pdf