So... About mid January, I walk into my barn and find a puddle on the deck of my Woods brush cutter. Now, it's under warranty at that point and I walk out of the barn wondering if the repair is as simple as I think it is and if its worth the hassle for the warranty work (loading it up, transporting it an hour away, reversing the process to get it back). "I'll just check online and if its more time than the warranty hassle is worth, I'll do it myself", I thought.
I found lots of folks asking the same question as me online, "what's involved?", but no details other than "it's easy" and verbiage on location/effort to change the input seal. My assessment was it was waaaay not worth the hassle of the warranty work and I chose to just do it myself when things warmed up. So, hey! Here are some details for others who run into an input shaft gear box failure on an implement. It is super simple and should be nothing to anyone who can hold a screw driver or work a wrench.
Here's my puddle on the deck... Plus some weird suicidal bugs that seem attracted to the oil. I found them in every oil pan in the barn. The puddle on the deck vs. near the output shaft is good news. On brush cutters in particular, output shaft seals are a pain to fix. Input shafts are eaaasy.
So, get rid of the shroud/shield for the uni-joint for ease of access. This involves pulling the PTO shaft off of the device in my case. The PTO shaft is typically held on to the spline of the gear box by a bolt that sits in a groove on the spline shaft. Remove the bolt/nut and the PTO shaft should slide right off the gearbox spline. Remove the shroud or shield by whatever means are required. 4 bolts held mine in place on the inside of the shroud.
OK, so far this may read as a cure for insomnia. There are numerous reasons for a seal failure. One big one is a failure of another component internal to the gearbox maintaining shaft center-line position. This will lead to bad bearings, if not caused by bad bearings and will cause repeated seal failures. Check the shaft for any play with the seal in... and later (if no play is evident seal-in) with the seal out. No give in mine thankfully! The pic is a bit misleading. After I took it, it was a full fisted grab, shove and shake on the shaft to check for play. The two finger tweak isn't quite what's required.
OK, bonus round! Most of us don't change our gear box oil every year, some of you do and you-all get a gold star... I am with the majority on this one. Extracting the oil will reduce the mess made when you pull the seal, so today we got an oil change. It's been a couple years - why not. Which brings us to another possible reason for an input seal failure... the vent on the top of gear box being plugged. That's coming out no matter what on my unit for an oil change, so it went into some spirits to get cleaned up while I worked on the rest of the project. A little screw driver actuation after it had soaked had it working great.
My oil extraction method is very low tech but it works. Most folks find draining these gear boxes a pain. Deal with it. DON'T PUT NEW OIL IN AFTER YOU DRAIN IT! That defeats the purpose of draining the oil to remove the seal w/o making a big mess. I almost did that exact thing just because I kind of go on auto pilot working on this type of stuff. Even if you decide to change the seal without extracting the oil first, I think you'd only lose a cup or so at most if you're slow... gear case oil is thick/slow to leak. You make the call.
Oh, a side note about the copper crush washers you (should) find under your vent and side plug. They're meant to be replaced after every tighten/loosen cycle. Mine were in visibly rough shape. Too bad I didn't have any of the right size handy... back on they would go later. Something to fix when I get some spares I guess.
OK, Oil is out, seal is exposed - time to pop it out. Have your new seal handy, there will be some oil in the bearings behind the seal which will leak when you remove the old seal, so hunting around the garage for the new one for 15 minutes will result in making a mess potentially. I found the best tool and approach for removing the seal was to use a fairly large screw driver inserted from the inner annulus surrounding the input shaft and prying the outer edge out working around the seal to get it out. 'Takes about 30 seconds with the big screwdriver, but its in there pretty good.. Replace the old seal with the new one, pounding it into place evenly about the circumference until it seats against the bearings. A section of 2" dia. pipe is perfect to seat it with.
Top off the oil, regardless if you changed it or not. Fill it until the oil starts to weep out of the side gearbox "drain"... Some oil was lost no matter how fast you are. And then, reverse the disassembly process. In my case, the PTO shaft stays off for slip-clutch maintenance later this week.
Hopefully, the next person searching for info on this really-too-easy-to-not-do-yourself repair on google will get redirected here. Sorry for the rotation of some of the pics, but you get the gist of it regardless. I didn't see anything like this online when I did my search, not that I felt I needed this level of detail, but content makes any site worth reading. Here's a bit (at the "change a light bulb" level of difficulty) for GTT!
For those of you who followed along and wonder, "who dunnit?" as to what caused the failure of my seal, I am suspecting this is it is the victim of an unheated barn over a very cold winter in our area (think thermal expansion/contraction). The leak occurred mid-winter during a cold snap and I didn't see evidence of more leaking as the weather moderated. I don't tolerate hardware failures well and leaks not at all, this stuff is almost a moral imperative for me to fix even if it may not be a big issue. It may well happen again next cold snap and I will have confirmation on the hypothesis. In the mean time, I have a known good seal.