1949 Model M transmission oil contamination - how clean

Purchased a really nice Model M a month ago. Transmission had water contamination, as expected.
I drained the milky fluid out, flushed with 1 gallon of diesel oil and drained that, added a gallon of motor oil to act as a flush. Still had quite a bit of contamination when drained.
Let sit for 2 weeks with drain plug open.
Added 1 gallon of GL-4 85/90 wt gear oil. Drove it around - still milky and some foam apparent.
Is there more than one drain plug? Per my factory shop manual, there is only 1 drain plug. And, the capacity is 6-1/2 quarts. Cannot add more than 4 quarts before full to the filler plug.
Looks like I will drain it again. Looking for suggestions. Maybe pull the shifter cover? Seems like 2-1/2 quarts of crud still in there, or I am not getting everything out.
Quality GL-4 isn't cheap, and I'd like to figure this out before buying more fluid.
 
Perhaps there is a build up of sludge preventing the oil from draining back from the differential portion of the transmission housing.

You could try jacking the back of the tractor up and see if more oil drains out?

If inclined you could remove the shifter cover and rear cover in order to do a better job by manually scrubbing with solvent and a brush or rags.

If it's been that neglected, no amount of "flushing" will get that crud out of there IMHO.
 
Let it sit a week and crack the
drain plug until the water seeps
out and tighten it back up. Use it
some and do it again. You should do
the finals too.
 
Yes, drove it around with the diesel flush.
Good idea about removing the belt pulley assembly and trying to clean the diff area. Hadn't though about that.
Already did the final drives - they were fine, No water, just that black lubricant I have seen many times in old tractors.

I presume taking off the belt pulley is not big deal. Will that allow a good view of the diff and any crud left in there?
Thanks for the help.
 
(quoted from post at 07:57:43 01/27/23) Yes, drove it around with the diesel flush.
Good idea about removing the belt pulley assembly and trying to clean the diff area. Hadn't though about that.
Already did the final drives - they were fine, No water, just that black lubricant I have seen many times in old tractors.

I presume taking off the belt pulley is not big deal. Will that allow a good view of the diff and any crud left in there?
Thanks for the help.

On second thought, maybe first step is to take off the shift cover. I am 70 and that belt pulley looks pretty heavy.
Can you see the bottom of the diff with the shift cover off?
 
There's no easy way to clean that
tar out of the bottom. Pulling the
back cover is the only way you're
getting it out. Only reason to pull
the top is for final flushing with
a pressure washer or solvents after
you drag out what you can from the
rear.

I changed the oil in mine last
year. Like you it didn't take near
as much oil as it was supposed to
to refill. I figure that tar
buildup laying in the bottom isn't
going to hurt a thing. The oil is
where it's supposed to be and
that's what matters. I crack the
drain plugs in all my tractors at
least once or twice a year and let
the water out. Even with a good
shifter boot you will get
condensation and have to do it
again.
 
Thanks, M-Man. I was hoping I wouldn't have to pull off the belt pulley attachment as it is pretty heavy for me to manage. I agree the buildup on the bottom should be left alone.... but it is clearly retaining some of the contamination behind it so not sure how will get that out. Might try to lift the rear of the tractor and see if that makes any difference.
I'll try another gallon of cheap motor oil and see if that will stir things up enough to get the water/oil mix out.
Will post a few pictures of progress. GL-4 gets more expensive every time I buy it.
 

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