Trim pump oil or trans fluid ?

[buzmacdowell]

Older trim pumps say 5/30 sae oil on them, but it seems that a lot of people use trans fluid...what is the best to use....and why?

[XstreamVking]

Use what it says, is my 2cts. Only difference would be a faster action with the thinner trans fluid.
Might have o-rings that won't like trans fluid though.

[Jim Speros]

I agree uses what says. I do however recall a time when ATF was what is said to use. I don't immediately recall an example other then a 3 ram system. It may have been an old K plane pump. I suspected ATF was used for anti foaming.

[Chaz]

If the pump and cylinder are fairly new (don't leak down) I use AW-32 (10 wt.) hydraulic oil. If it's going in a Powerglide or turbo 400 with a trans brake, I add a quart of F-type ATF to a 5 gallon pail. It gives the fluid some color, so I or the owner can see when (if) it's starting to blacken the plates and band.
If it's going in something that's gotten loose over time (or I want to tighten the converter a couple hundred RPM) I'll use AW-46 (15 wt) .
My Motion has a Capalino helm and old azz Marine Machine rams .. (both have been gone thru) I use AW-32 for the steering as well ... :thumbsup: