Posthole Digger Post Hole Digger Repair - Leaks Oil

[zuiko]

I haven't used my PHD for a while but it's been leaking oil through the four bolt flange where the input shaft goes into the gearbox. It's got a triple gasket arrangement which I am pretty sure is where the problem lies. What was in there were is a stack of three very thin gaskets - two thin metal (different thicknesses) and one super thin plastic.

Any suggestions on replacing that seal? I'm sure to order the parts from the manufacturer would probably cost more than they are worth and take a while to get to boot, if I can even find someone to order the correct parts. Is there an off-the-shelf replacement I might be able to get somewhere? They are just circular 4-3/4" O.D. and 3-1/8" I.D. with a 4 bolt pattern. Or could I just use a tube of make-a-gasket and bolt it back up?

 

[flyerdan]

So it's not a shaft seal, but the assembly? The metal shims are to give the correct toe contact to the gears, so they are important. Should be pretty straight forward, clean everything of old sealer and check for nicks or gouges, paint everything with a thin coating of Permatex or even better, Spray Tack.
Pay attention to the inside corners where the bolts go through, sometimes if they don't seal oil will wick through the bolt and show up under the head, where it spreads to the rest of the assembly.

 

[zuiko]

Yes the oil seems to leak from where the flange mates, not the shaft seal. The steel gaskets are no longer flat. The plastic gasket has a tear around the bolt holes. According to landpride the thicknesses are 0.1mm (assuming that's the plastic one, but they don't say), 0.15mm and 0.5mm which would be about a 26 gauge and a 38 gauge on the steel gaskets. Not sure why they use three pieces instead of one or two.

Wouldn't the permatex by itself add some gap to the connection? Maybe 0.75mm worth of gap? I'm not sure how thick a squished bead of permatex is.

Edit: I could probably also flatten out the 0.5mm thick steel gasket best I can and then coat both sides of it with permatex and reassemble. That would be another option.

 

[flyerdan]

I would imagine that the shims are stock thickness, like on a car front end, and you stack as many as needed to get closest to what you need. Gasket sealer won't add that much to the overall thickness; like wood glue, most of it will squeeze out which is why it should be used sparingly where it might migrate to the innards.
I'd flatten out the shims as best as I could with a plastic hammer (metal head would probably take it out of true, like beating on a penny) and install the plastic gasket with the tears around the bolt holes facing upward, if that's possible.
If it was a pretty small leak to start with, I suppose when it was all back together you could run a bead of rtv silicone around the seam as an added precaution.
Chances are they are standard parts stocked at lots of dealers that work on implements, note the sizes and take a picture of them so you can check the next time you're at the shop if this fix doesn't work.

 

[woodlandfarms]

Please wait for someone else to confirm but the work around used to be just drain and replace with grease. Like Axle Grease.

 

[Fallon]

Please wait for someone else to confirm but the work around used to be just drain and replace with grease. Like Axle Grease.

I did that on the gearbox for my old flail mower. Pourable grease works well & wont leak out of failing seals. Not ideal, but likely to outlast the rest of most older impliments.

 

[RickB]

You can measure the shim thicknesses with calipers and replace them with a like amount, or use a gasket sealant as suggested. Do not eliminate them, doing so puts the input shaft bearings at risk. Multiple pieces are used at manufacturing to achieve the proper bearing preload. A very common gearbox design strategy. Thicker grease is a good option.