Rear Axle Seal Replacement

I would really like to thank "AGirlAndHerTractor" from our message board for this excellent write-up.

Long story short, you cannot easily remove the axle to get to the seal on the 1601. The entire back end of the tractor must be disassembled. Other Yanmar models are engineered a little different - some may use this procedure and a few you can actually remove the end of an axle much simpler.

[ This covers pretty much all of the models with the one piece rear axle (does not have a removable hub)]

First, remove wheels, rear fenders, roll bar, and seat assembly. Next, remove the hydraulic assembly that sits on top of the differential. It is heavy. If you've never had this part off before the gasket will make it tough to remove. Use a pry bar in this location to help break the seal: 




Now you'll have access to the PTO assembly which must be removed. Do not be tempted to pull just the shaft out. The entire assembly has to come out as one piece - this will make more sense as you look at the assembly diagram in your parts book. Leave it together and remove the whole hunk.



The PTO cover may also be very hard to remove. Use some sharpened flat screwdrivers to begin seperating the cover from diff. assembly. Use care here. 



Before attempting to pull the PTO unit out, note that the PTO speed selection shaft prevents it from sliding out more than an inch or so. 




There's a bolt on the left side of the diff case that holds the PTO speed selectotion shaft in. Remove that bolt and gently nudge this shaft out by 10mm or so - it won't come all the way out and only moves a few mm's - that's all you need. Now the PTO assembly can be removed: 

Now that you have the axle removed, you may take some time to remove any remaining gasket material from the differential housing. Once that is done you will want to clean the inside of the differential case including the hydraulic oil screen.

Next, put the axle on a workbench. You'll need to press the outer bearing off the shaft. I didn't have a puller with extra long arms, so I made something that worked just as well.

This jig is four 5" 3/8" threaded bolts with four washers and nuts. I'm careful to hold the bolt still while the nut is spun with a wrench. I guess you could spin the bolt but it might leave score marks on the axle. YMMV



The collar will still be lightly pressed on the shaft. A pry bar will pop it right off. 



Collar removed:



Here's the new seal and collar assembly that replaces the old parts:

ASSEMBLY

First apply some grease to the seal:



And to the bearing surface on the shaft too: 



I used a section of 2" PVC pipe to drive both the seal and bearing down on the axle.

Remember the washer that goes next to the snapring I mentioned earlier? Well that has to be tossed into the axle housing and put on the end of the axle shaft as it slides in. It won't fit through the housing if it's actually slid on the axle. Weird but once you see the housing this will make sense.

PITFALL:
You may be tempted to bump the axle back in place and tighten the four flang bolts. Don't, you have to get the dog gear on first. I speak from experience:  



Getting the axle and dog gear back in place is not easy since the inner bearing is lightly pressed into the housing, and tightly pressed on the axle. It wants to push off of the housing every you tap the axle in.

I don't have pictures here because I literally had my hands full with what I was doing. I got a porta-press from Harbor freight and used that to help push the dog gear and inner bearing back onto the axle and into the differential housing. If that last sentence sounds complicated that's because it is. You'll need the porta press, 10mm press attachment, and some spacers that will hold up to some pressure. Use extreme care here - not only for your own safety but you don't want to break anything. Go slow and know what you are doing in advance. Wish I'd taken pics of this stage but it was messy. You may find a better way of doing this.. if so, post reply with info.

Here's the left dog gear reinstalled.



Differential all cleaned up: 



The last thing is to reinstall the PTO assembly and hydraulic cover. I won't list out step by steps for this.. just read through disassembly and basically reverse it.

 

I would really like to thank "AGirlAndHerTractor" from our message board for this excellent write-up.