Several of my old tractor manuals mention washing oil for flushing gearboxes and crankcases. An Internet search yields almost nothing. Does anyone know what it was, and what do you currently use? Especially to flush a running engine without risk of damage.

I have heard that automatic trans fluid is very high in detergents and can be mixed with the engine oil. Any thoughts?

I'd also like to hear some of the horror stories of what you have found while draining long-neglected gearcases. I'll start:

When I was going thru my JD Model D I swear the goop in the final drive case was the factory oil (1942). It was the color and consistency of brownie batter, and took a week to mostly drain out. I ended up hooking my pressure washer to the water heater in my RV (propane fired- makes scalding hot water). That got most of it, then I ran it for while filled with diesel with some 30w added for lubrication. Good thing, because I needed all that diesel to thin the goop enough to put in the waste oil!

Years ago, I drained the trans. of a JD H, & the stuff was like liquid plastic...it formed a cone in the middle of the drain pan & took about 15 min. to flatten out. I was actually able to put my finger against the stream & push it over an inch or 2 to the side, & it just slid around my finger. I've never seen anything like it since. We kept the pan of stuff around the shop for a while just to play with, you could turn the pan upside down & it wouldn't run out. Another time I went to drain the engine oil out of an old A, & had to poke a screwdriver up into the hole to get it to drain. there was almost 2" of hard crud in the bottom of the case...
As for washing oil, I don't know what it might have been, I've always used Diesel to flush gear cases.
Ron in CO...

I had a friend of mine that worked on old tractors. He made up an old electric hot water heater (5/10 gall ) and an old sump pump and he would heat up ATF fluid and pump it in to the final drives etc and catch fluid in an old pan. The pump sat in the pan pumped oil into the heater through a hose to a hand wand with the end crimped so it would spray off to one side he could move it around (either going through the fill hole or an inspection hole) and get a lot of crud cleaned out. The warm oil seamed to really cut the crud. The oil probably was about 100deg not real hot.
May not be practical in your case but worked well for him.
I have also heard of people using straight Bio diesel to soke gear boxes etc the biodiesel seemes to cut gunk lose beter than regular diesel.

Russell