Oil

[Mark Page]

I've noticed that the gear box on my Woods mower has been hot after only an hours mowing. I pulled the hex plug out and some oil trickled out. I decided to replace it and called my dealer. He said pull the top cap off and siphon out the old oil. This sounds a little impractical. He also said to use 80w-90 gear oil, which I have never heard of. I think I'll probably sop the old oil out with rags. He said a new gasket should be made with RTV Red Permatex gasket material.
Does all this sound correct?

BTW- The owner's manual mentions none of this, except the level plug.

 

[KML]

Sounds like he's given you solid advice! The siphon he's talking about is most likely one of the little hand siphon pumps you can get at walmart and most auto parts stores for ~ $10, not mouth siphoning like when teenagers used to steal gas (not that any of us has ever done that, but we've heard stories):thumbsup:.

As far as 80W-90 gear oil, it's probably the most common gear oil out there and available anywhere that sells gear oil. If that's the weight the manual states, you can't go wrong with it. I personally use a good synthetic like royal purple in gear boxes because of the heat and relatively low cost as they take so little. Can't point you to any science as for why it's good to do it just makes me feel warm and fuzzy..

RTV for a gasket is good to if you apply it correctly. Here's what I do - Clean both sufaces, run a bead about 1/8" in diameter, let it set-up for 10 or 15 minutes, place the cover on and start the bolts but leave them loose! let the RTV set-up for at least another hour or so (or over night if your not in a hurry). Tighten the bolts and your done.

The two biggest problems many people have using RTV:
1 - not cleaning the mating surfaces.
2 - squeezing all of the sealant out by wrenching the cover in place while it is still wet.

Also, be careful with rags, not a huge deal with a gear box but when cleaning rough cast surfaces they can leave as much lint behind as junk they take out. If you ever want to see how much lint regular rags leave behind, rebuild an automatic transmission with them. If your lucky it'll go 100 miles more likely about 4 blocks:ashamed:

 

[kebo]

The problem with the oil getting hot inside the gearbox is that it will expand some and that can build pressure inside the box. This can cause the oil to weep past the seals, and possibly even damage them such that they don't seal good and eventually have to be replaced. There are some plugs that have a vent in them, which will let the inernal pressure vent to the outside. I'm looking for a vented plug to fit the gearbox on my bush hog, but haven't had any luck finding one yet.

 

[MHarryE]

Doesn't the gearbox have a vent? Think of the gearbox - small oil volume but transmitting a lot of power. It is going to get hot because there is no cooler to get rid of the heat except the walls of the gearbox. I always switch my equipment with gearboxes to a top quality synthetic. General spec is always 80W-90 gear oil. I generally run Caterpillar Synthetic Gear Oil because the Cat dealer is close and the price is reasonable compared to other synthetics. It is 75W-140 and has a 50 degree higher temperature capability than straight mineral oil. I noticed I also have Valvoline and Mobil 1 synthetic gear oil in my cabinet - Cat's smallest quantity is 1 gallon and my outboard lower unit uses only about a quart.

 

[Mark Page]

The top cap has a pressure relief valve in it.
Thanks for all the advice.
Mark

 

[Mark Page]

Sounds like he's given you solid advice! The siphon he's talking about is most likely one of the little hand siphon pumps you can get at walmart and most auto parts stores for ~ $10, not mouth siphoning like when teenagers used to steal gas (not that any of us has ever done that, but we've heard stories):thumbsup:.

As far as 80W-90 gear oil, it's probably the most common gear oil out there and available anywhere that sells gear oil. If that's the weight the manual states, you can't go wrong with it. I personally use a good synthetic like royal purple in gear boxes because of the heat and relatively low cost as they take so little. Can't point you to any science as for why it's good to do it just makes me feel warm and fuzzy..

RTV for a gasket is good to if you apply it correctly. Here's what I do - Clean both sufaces, run a bead about 1/8" in diameter, let it set-up for 10 or 15 minutes, place the cover on and start the bolts but leave them loose! let the RTV set-up for at least another hour or so (or over night if your not in a hurry). Tighten the bolts and your done.

The two biggest problems many people have using RTV:
1 - not cleaning the mating surfaces.
2 - squeezing all of the sealant out by wrenching the cover in place while it is still wet.

Also, be careful with rags, not a huge deal with a gear box but when cleaning rough cast surfaces they can leave as much lint behind as junk they take out. If you ever want to see how much lint regular rags leave behind, rebuild an automatic transmission with them. If your lucky it'll go 100 miles more likely about 4 blocks:ashamed:

I have a siphon hose with a bulb type primer, but I don't see it working very well with 90 wt. oil. The diameter of the hose is too small. Works great with diesel fuel.

 

[RavensRoost]

Use a suction gun, sort of looks like a grease gun. Here is one at the 'freight yard' for less than $10:

Oil Suction Gun

 

[bilrus61]

Gearboxes get hot after just a few minutes use even if well lubricated. Dealer has told you right on the oil and all. I use a 1/2 inch clear plastic hose like you find at the TSC store. Just run it till it gets a bit warm. Take out the top fill plug, stick in the hose, suck up the oil and then lay the hose over to a pan and it will all siphon out. Get 7 feet of hose..... It would be better to turn it over and drain it but easier to do it with the siphon hose twice. I figured that gets any stuff thats bouncing around in there out. Takes about a hour to drain my gearbox on my mower. You just start it at kickoff and fill it back up at halftime.

Oh if its leaking out the side "check plug" just use some teflon tape and that will seal it. Tape cost about a buck. I use 80/90 because its a bit thinner and I think gives me more horsepower at the blade.......I have no idea on earth if that is correct........:confused2:

 

[KML]

This is the pump I use. They don't last forever when used with petroleum products but they work well and are cheap. It has 1/2" hoses so gear oil is no problem.

Walmart.com: Custom Accessories Pennzoil Multi-Use Hand Pump: Team Sports

 

[kebo]

The top cap has a pressure relief valve in it.
Thanks for all the advice.
Mark

Glad yours does, the gearbox on my mower doesn't have a relief valve on it. So, I am stuck trying to find a plug that has a vent made into it.

 

[mrutkaus]

Putting a little gear moly in seems to make things work better for me.

Mike

 

[Oldmopar]

If you need a vent plug go to any heavy truck parts place, even Napa, and ask for a vent for a rear differential. They work very well and are usually the same size thread, if not pick up some adapters as well.

 

[Chilly807]

Even in the heat of summer, my rotary cutter gearbox only gets warm to the touch, not what I'd call hot. It was shipped with a plain plug in the gearbox, and a vented one in an attached bag to replace the solid one once it was in service.

The anaerobic sealers such as Loctite 515/518 etc won't harden until there's no air in contact with the sealant, so simply tighten them to the snug point and wait 24 hours before adding oil for the best results. A final tighten won't hurt matters any, and they will work if you add oil right away too, but it's not ideal.

I've only ever used plain old 80w90 gear oil and had no problems, but there's no harm in using the high end synthetics if it makes you feel better.

Sean

 

[Short Game]

The gear box on my Bush Hog finish mower has always gotten hot. It was old when I got it. I had to put new seals in it once. I figure they just get hot. I run mine for hours at a time. It gets hot. Most of my seat time is running this mower. There is a little bit of gear oil in a small case. Why wouldn't it get hot?

Hot, warm? Those are relative terms. Mine gets quite warm.