Yellow oil in transmission???

I changed the oil in the transmission case. It is 90-weight gear oil, and had been in that tractor for at least five years (we don't use it much). The oil came out a bright yellow color. It had gone in as normal dark brown gear oil. I shrugged it off as a possible reaction with water.

I filled the transmission case with new oil -- 20 quarts. Then I ran the tractor in freezing temperatures for about half an hour. Then I realized that I had used regular crankcase oil (10-40 weight) instead of the 90-weight gear oil. So I quickly drained that oil. It, too, came out yellow.

What in the world would tint regular automotive engine oil bright yellow?

The tractor is a 1951 Ferguson TO-20.

Is the oil having some kind of reaction
With the paint inside the gear case?

Water

I doubt that it's from paint; the color in the second batch is identical to the color of the first batch. If it were merely mixing something yellow into the oil, we'd see spottiness and a diminished coloration in the second batch.

Besides, who paints the INSIDE of a transmission case???

Nevertheless, your explanation is the best I've got so far. My guess is that there might be some sort of chemical reaction with some old deteriorated rubber part. But that's a LOT of oil to react with!

Yes, yes, that's EXACTLY what it looks like! Can you explain what's going on here?

You have water in the oil. It gets into the tranny by running down the shifter through the shifter boot and down the lift spring control plunger (the deal that the top link hooks on to).
Let the tractor sit for a few days, then loosen the drain plugs and drain all the clear water out. It doesn't take much water to turn the oil yellow.
BillL

Wow! I would never have expected that water reacts with oil to produce that effect. And yes, the rubber fitting at the base of the gearshift knob is broken. I shall see if I can find a replacement that fits at an auto supply store.

Thanks so much for the help!!!

BTW, it doesn't hurt to use 10W-40 oil in the transmission. The lighter oil can actually help the hydraulics to work better in really cold weather.
You would have to do a lot of work to get all of the water out of the cases so that the oil won't discolor again. A small amount of water doesn't seem to hurt anything other than making the oil yellow.
BillL

The gears, and hydraulic pump tend to mix the water in the oil a lot more than it does in a engine. After a few oil changes it will go away, the water gets in when the tractor is parked outside. Covering it with a tarp, or parking it a shed helps a lot.

Your experience is very common. There is a thread about it here virtually every other week. Though having a good gear shift boot is good, don't expect a boot or a roof to keep the water out. All gear cases are vented to keep the bearings from being ruined by the constant expansion and contraction of the air in the case. If you work your tractor and get the cases hot, as it cools some air will be drawn in. If the humidity is high, there will be moisture being drawn in also, If it gets cold that night and the housing temp gets below the dew point, suddenly there will be condensation on the inside. Have you ever seen condensation on a heavy piece of cast iron? or on concrete. The same can happen in your engine crankcase, except you will get moisture as a product of combustion in it every time that you start it. Normally a car or truck engine heats up enough in just a few minutes to drive the moisture off, but tractors often have a more massive motor and need to actually do some work for a little while to drive the moisture off. Starting a small tractor engine and letting it run for five minutes is as bad as a two mile twice a day commute is for a car.

Is there any way to know how much water in the innards is "too much"? Or is it a matter of "all water is bad, and more water is worse?"

Water,moisture in the oil.I see it in old tractors all the time in the hydraulics
and tranny.

You can order the boot online, possibly Tractor Supply would have it.

I used a cut off CV joint boot for several years, worked great, held up better than the aftermarket boots.

The reason the color keeps coming back is when the gear case is drained, some contaminated oil stays trapped inside, no way to get it all out.

A little discoloration won't hurt it. Main thing is to keep it under cover to prevent more contamination. If you can keep it inside is best, under a roof is better than nothing, but tarping can cause even more condensation and is a rat haven!

OK, so for now it's a tarp in the rain and I'll clear out some space under a roof to keep it dry once summer comes.

Thanks for all the help.

first 90 wt. gear oil is the wrong oil for the to-20 it should be GL5 mineral oil big difference in oil type GL5 is very yellow out of the bucket but oil will turn yellow from oil.i have 5 TO'S and run GL5 in all of them and not ounce of trouble that way i don't have to fix anything

should be from water

Older tractors are bad to condense water in the transmissions just from air temperature changes. They will look like that after a few years even if stored in an insulated (not heated) building. When they were newer and used as intended, plowing, disking, cultivating, etc. as they were intended, the transmissions got warm and stayed warm enough to evaporate the water. Now however most of them get pretty light use and the transmissions never get very warm so the water does not evaporate out. In addition to some other tractors, I have my Dad's Farmall H he farmed with for 45 years. In that time it never showed signs of water in the transmission oil, but setting in my shed and only being driven around the place every 2 or 3 months and 5 miles to town for a parade once a year it needs the transmission oil changed about every 5 years or so. 15 gallons. :twisted:

(quoted from post at 19:44:11 03/07/17) OK, so for now it's a tarp in the rain and I'll clear out some space under a roof to keep it dry once summer comes.

Thanks for all the help.

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Now why would you cover it with a tarp when Steve tells you that it is not a good practice?

Sounds like the transmission retained a lot of water when you first drained it and just mixed with the new oil.If you are going to drain it again before you do pour in a can of
Seafoam and drive the tractor around to get it all throughly mixed and pick a warm day then study where the drain hole is located in relation to the rest of the transmission then park the tractor so you get maximum amount of drainage drop the drain plug.Then leave it for awhile to make sure you get all you can get drained.Condensation will happen but its over a long period of time.A cover over the tractor is better than no cover for sure.

(quoted from post at 19:44:33 03/07/17) first 90 wt. gear oil is the wrong oil for the to-20 it should be GL5 mineral oil big difference in oil type GL5 is very yellow out of the bucket but oil will turn yellow from oil.i have 5 TO'S and run GL5 in all of them and not ounce of trouble that way i don't have to fix anything

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GL-5 *IS* gear oil, or more accurately, a specification for gear oil. Could be 90, or 75W-90 or 85W-140, but anything that meets the GL-5 spec is a heavy gear oil.

Sounds like water . maybe need new rubber seals around the gear selector thats generally where alot
comes in from.

I have come up with one idea: I'll use a hair dryer to pump hot air into the transmission to evaporate a lot of water. I'll have to open up both the fill plug and the drain plug, and even the hole for the dipstick, to maximize the air flow. I'll let it run for a day, then seal it up and keep the tractor under a tarp until rainy season ends in a month or so. After that, it will be kept under a roof.

I'm probably going to extremes, but inasmuch as I change the oil only every five years or so, it's probably worth the time.

The good news is that, when I do run the tractor, I tend to use it for at least an hour at a time, so it should drive out the water during those times.

Again, thanks for all the help, everybody!!!

(quoted from post at 08:23:35 03/08/17)
I have come up with one idea: I'll use a hair dryer to pump hot air into the transmission to evaporate a lot of water. I'll have to open up both the fill plug and the drain plug, and even the hole for the dipstick, to maximize the air flow. I'll let it run for a day, then seal it up and keep the tractor under a tarp until rainy season ends in a month or so. After that, it will be kept under a roof.

I'm probably going to extremes, but inasmuch as I change the oil only every five years or so, it's probably worth the time.

The good news is that, when I do run the tractor, I tend to use it for at least an hour at a time, so it should drive out the water during those times.

Again, thanks for all the help, everybody!!!

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That is FUNNY!!

Where are the vents on the A,B,H and Ms and others there isnt any lots of other tractors dont have a vented tranny and they dont get moisture unless out in the rain.

(quoted from post at 14:59:43 03/08/17) Where are the vents on the A,B,H and Ms and others there isnt any lots of other tractors dont have a vented tranny and they dont get moisture unless out in the rain.

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Gene, you know that crankcases, differentials and transmissions have been vented on cars and trucks for many years. Expansion of gases with heat and compression with cold is a very basic fact of physics. Before engineers and designers started designing purpose made vents in, the air went in and out through places like around PTO shift levers 3 pt lift arms and the like. If the only places available were axle, input shaft, and PTO seals, well that is where the air went in and out. Vents are not there for decoration or in order to have something extra to charge for. They are necessary to prolong the life of seals. to reduce the suction of dust into the seals. Air is going to move in and out, and moisture with it. Moisture will condense on a cold surface. You cannot tell me that you have never seen moisture condensed on the cast iron of a tractor on a cold morning or even mid-afternoon when a humid air front comes through. Well if it condensing on the outside, it is condensing on the inside at the same time. How would you separate the water vapor from the air? Read John cub owner's post, and check your tractor's gear cases!!

A bit of a followup: To make a long, long story short, the transmission case has always had a tiny crack on the side where a broken moving part smashed into it from the inside many years ago. That crack had never leaked -- until a few months ago when I ran the tractor for several hours in very cold weather. Apparently the thermal stress of the rapid warmup opened up the crack and it started leaking again.

I called a mobile welder and asked if he could repair the crack. He explained in detailed technical terms why the weld probably would not hold. The only way to get it right would be disassemble the entire transmission to isolate the cracked side. Instead, he recommend that I clean out the crack and try some steel epoxy.

The first thing I did was to take a heavy hammer and hit the protruding side of the crack (it was only about a millimeter out from the rest of the case). I was able to push it back so far into place that the leak was reduced to about a quarter of its original rate.

After letting the yellow oil drain for a day, I put a hair dryer into the fill hole and let it run for several hours. The transmission casing closest to the hair dryer got pretty hot -- well over 100ºF.

So while I was heating the inside of the transmission, I scrubbed the area of the crack down with a fine wire brush and acetone, working really hard to get the bristles deep inside the crack.

Next I let the metal cool to about 90ºF and then applied the epoxy. The warm metal softened the epoxy so that it went readily into the crack. Then I gave it 24 hours to set.

This morning, I filled the transmission with 90W oil and ran the tractor for about half an hour. I let it cool for an hour and then checked it. The epoxy has held -- so far. But when I checked the new oil, it was yellow. Sheesh, NOTHING will get that water out of that transmission!

I wouldn't worry about it at this point.