Advice on changing rearend and transmission 90 wieght oil.

I have a 53 SM in checking rear oil level I find it is Black and very thick, even a gelatin like texture. It seems that it may be the original oil, and needs to be changed. How should I go about this? Such as: Should I heat up by running tractor before draining? should the rear be rinced out with kerosine or deluted in anyway? Thanks

I changed some nasty tranny lube out of my Super M a couple years ago. A few things I learned:

1 – Have at least (3) empty 5-gallon pails ready to catch the old oil. If the transmission is filled to the “full” level you’re gonna get 13 gallons of stuff when you pull the plug. (That’s a lot of dirty oil arrives in a hurry once the plug is out!)

2 – Drain the oil on a hot day if you can. The warmer the old stuff is the faster it will drain.

3 – Park the tractor so the front end is higher than the rear before pulling the drain plug. This will facilitate draining.

4 – If your SM has a belt pulley, loosen the gearbox housing to drain the quart or so of oil held in the gearbox.

5 – If you can let the tractor sit with the drain plug out for several days to let as much of the old stuff drain as possible.

6 – Some like to fill the transmission with kerosene or diesel as a flush, drive the tractor a few minutes then drain it. (I however skipped this step with mine…).

7 – Before dumping the old oil take a moment “go fishing” in the waste oil container(s) with a magnet. If you find any loose balls, whole gear teeth, etc. the transmission needs attention(!).

8 – Refill with 13 gallons of fresh oil.

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Hope this helps...

That's quite the comprehensive checklist there, Bob! I'll be savin' that one. #7 is an especially good point to my mind.

Related to #6 -- something I do that isn't exactly precise, but is helpful in estimating how much sludge I might have in an unknown tranny is to top it off (before draining) to the full level with diesel or kerosene and run it a little bit as you suggest. Using the little bit of diesel or kerosene at this point is not so much for scrubbing, but does have some of that effect. If it will take any significant amount, though, it does help thin things out a little to help with draining. Then I measure as best I can what comes out when I drain it. Not precise, as I say, but if I were to get two full five gallon pails out of an M and only a gallon in the third pail, that would suggest that there's something like two gallons worth of sludge stuck in there, especially if it was necessary to dig out any of that dry caked up sludge inside to get the drain to open up and run.

If what I get out is significantly less than what should be in it when it's full, then I proceed with #6, perhaps even driving it around two or three times over several days on one fill, before draining again.

Of course, refilling with fuel is not the relatively cheap proposition that it used to be! And it's a little easier to handle the waste with my tractors, a SuperC (5 gal) and a BN (5 quarts) than what's gonna come out of an M!. In the scenario I described on an M, you could wind up with as little (??!) as thirteen or as much as 25 gallons of stuff to get rid of and that's a lot of buckets. But the local garage with the waste-oil burner will be glad to make your acquaintance. 8^) And if one were to have filled it with diesel and were patient, he could keep it around after he drained it, let it settle and use it for cleaning parts down the road.

My SuperC as an example, was low to start with (the typical leaky seal on one of the axles -- bull pinions for the brakes were good) and took cloe to a gallon of diesel. When I went to drain it, I had to fish and poke with a screwdriver and wire to break up the cake in the bottom. I was only able to get about 4 gallons to drain, all pretty milky and brown. I gave her a few runs full of diesel and got more like 4-1/2 out. I fished around the bottom a bit more with a bent wire and got a little bit but not much more out when I flushed some more diesel down through from the fill hole. Close enough to refill her with 90W and run her for a few years. When it came time to think about changing it out again (a check through the fill hole showed her gettin' murky from condensaton) she was a little low again (seal not yet fixed). Topped her off with just a little diesel, ran her once just long enough to warm things up, and got pretty near the whole five gallons out like I should.

To be fair, the downside of running it enough to warm up with diesel in the tranny is that it might dissolve any sludge that was keeping seals from leaking (you hear this argument alot about flushing automatic trannies in cars), and find yourself with a whole new set of things to replace.