Water removal

Anyone ever tried heating up a tractor rear end with a space heater after draining the oil/water out? I'm tempted to try it and see if more of any lingering moisture could be removed from the drained rear end before replacing with new oil.
Maybe the water could be cooked from the 90 weight gear oil too if it's not dirty.

I've never found a good way to get it all out once it's emulsified into the oil. Maybe flush it with some diesel to thin the remaining oil and encourage more of it to drain. Heat would also help thin it but even if the water were evaporated it would still be trapped inside the case.

Any idea how the water got in? Bad shifetr boot?

Maybe get it as clean as it will drain over a few days, then refill it and check the drain occasionally (before use) to see if anything will drip out.

No matter how transmissions are drained, there always seems to be contaminated oil left in recesses. I've used baling wire tied to rag pieces, that fit through whatever holes are available, to mop out the oil. It's a pain but it does make a difference.

You might try some dry gas in the wet fluid before you drain the trans. The more expensive fuel injector grade (isopropyl alcohol) is a lot more soluble in oil than the cheap (methanol) stuff. Isopropyl alcohol should mix well with hydraulic fluid. If you drain the oil first, then flush with diesel and dry gas there will be a lot less water for the alcohol to remove.
{edit: If you don't drain first, there can be enough water to pull the alcohol out of the oil. If that does happen, the volume of the alcohol/water phase should be in the bottom of the sump and large enough to drain out. }

A quick search online found a test where 15% isopropyl was used in diesel fuel and run on a dynamometer, so it does mix well with diesel.

It won't cost much to try mixing an ounce or two of alcohol in some hydraulic fluid to see how miscible it is. I would run it long enough to mix well, but not under heavy loads.

EDIT: Back to the original questions.
If you drain the rear end and warm it up you will have to circulate dry air through it to dry it out. If you remove the drain plugs and run hot air through it with a heat gun or hair dryer, it will eventually dry the rear end out completely. The questions now are how long and is it worth the effort. A propane fired heater puts out a lot of moisture, so for drying things electric heat is better.

Drying the oil is the same principal. You have to blow low relative humidity warm air over or preferably bubble it through the oil. The hotter the better within reason. Hydraulic oil breaks down with heat and moisture, so there is the possibility that the water in the fluid has degraded it enough that drying it isn't worth the effort.

(quoted from post at 17:12:22 01/28/23)Heat would also help thin it but even if the water were evaporated it would still be trapped inside the case.

Click to expand...

You will not have much water. If you have any amount of liquid water in there and heat it until all of the liquid has evaporated with all of the plugs open, the relative humidity inside can't be over 100%. So warm it up, let it breathe and she'll be right, no worries.

I don't know exactly how big the case is. 10 is an easy number to use, so let's say the case volume is 10 cu ft. If the plugs are open, and air is free but not forced to circulate, the maximum amount of water vapor that a 10 cubic of air can contain at 100% RH and 90F is about 10 grams. At 70F and 50% RH, there will only be about 2 grams of water vapor. You have maybe 20 liters of oil so 0.01% water to dissolve in the oil.

Weight of water vapor in air




This post was edited by Dave G9N on 02/08/2023 at 11:22 am.