Gearbox Rebuild / Change that Hyd. Oil and 90W !

[richhiway]

 

 
I picked up this mower on a online auction. It sat a long time and the 90W leaked out the lower seal. I had hoped to change the seal but condensation rusted the bearings. I know this isn't a sawmill but I thought it might help out with someone needing to rebuild any kind of similar part. It also is a great example has why you should change fluids. Sometimes we think that hyd. and gear oils will go forever but condensation and rust are killers of gars and bearings. I'll take more detailed pics of the reassembly after the parts come. Oil is cheap. Parts are expensive.

[richhiway]

 

 
Sometimes you can not get power tools on a tight bolt. Never forget the basics of leverage. A few pieces of common pipe are a mechanics best friend. If you are going to be doing your own repairs I would recommend that you get a few sets of Snap On six point flank drive sockets. Yes there really is a difference. While expensive, they will save you a lot of stripped bolt heads and aggrevation. You can pick them up used on criagslist or ebay. The cheaper imported tools are OK most of the time but will slip or break when you put them to the test.

[dgdrls]

Just because it checks full doesn't mean its set.
Change ALL those fluids regularly

D

[richhiway]

 

 
Removed the gearbox from the mower deck to get to the seal behind the pulley. Give the pulley a spin and bad news! A very rough sounding bearing. You need a little experience to know the difference between a serviceable bearing and a bad one. In this case it was obvious. A good bearing with life left in it can make noise but should spin freely with no roughness.On inception the balls races and or roller can be burnished grey but should have no imperfections or corrosion. These bearings run in oil. Some sealed bearings that are noisy life can be lengthened by popping out the plastic seal and packing them with fresh grease. Especially in a pinch when you don't have a new bearing.

[richhiway]

 

 
When you have to remove nuts from a rotating shaft it is best to clean the threads with a wire brush to ease removal. This goes for any dirty or rusty threads.

[richhiway]

 

 
Penetrating oil,Penetrating oil,Penetrating oil!! Anything that moves needs lubrication. Save yourself a lot of aggravation and time and money. If you know your going to take something apart and you have time soak everything with penetrating oil for a few days. On reassembly put never seize, grease or oil on anything that moves or that you may need to take apart again. Clean lubricated threads will tighten to the correct torque evenly. It is the stretch on the bolt and lock washers that keep fasteners tight,not dirty threads. I also keep exposed threads coated with white grease or fluid film on all my vehicles and equipment.

[richhiway]

 

 
A big air gun helps on big nuts. I was able to hold the pulley with a rag and spin the nut right off. If you have to do it by hand and can not jam the pulley with a bar,sometimes you cab wrap the belt around the pulley and jam the belt tight with a pry bar.

[richhiway]

 

 
This pulley was rounded on the back and did not lend itself well to a puller. Lucky for me my brother stopped by just as I was trying to remove it.  Most of the time you can put tension on the pulley or gear with a bar and a block of would and then strike the shaft with a hammer or an air chisel and the part will come off. On threaded shaft screw the nut back on to protect the threads. Here we used a brass hammer between the shaft and the large hammer.

[richhiway]

 

 
A seal remover hook is a inexpensive and handy tool. If you don't have one use a pry bar or a screwdriver to pry out the seal.

[richhiway]

 

 
Snap rings. They come in a lot of shapes and sizes. You usually need the right tool and patience. Usually if you tap them around with a hammer and a small punch to brake them loose they will be easier to remove. Sometimes you just have to ruin one and replace it.

[Kbeitz]

You need one of these to get behind some pulleys and bearings...



 

[richhiway]

 

 
Here comes the tricky part. If you do not have the directions and are taking something apart for the first time it pays to at least go online and take a look at the parts diagram. Once you have removed the clips, you need to determine the direction of disassembly. In this case the shaft had to be driven forward to remove the bevel gear,then the shaft driven back to remove it and the front bearing. Be careful to look for shoulders that bearings rest against. You can crack the housing if you get too rambunctious forcing things in the wrong direction. If you hit something and it sounds solid,it probably is.

[richhiway]

 

 
Once the upper shaft and gears was removed. the lower shaft can be driven up and out. The lower of the two bearings is then driven out the bottom.

[richhiway]

 

 
The last thing was to drive out the front seal. Also watch for shims as you take the shafts apart and note there position. A large hammer and heavy punches make easy work of driving things. On stubborn parts you can not beat a air chisel. Don't be a afraid to use a big hammer!
Now you have to clean everything up and order the parts for reassembly. I will post those pics next.
I hope this advise was not to basic. I am sure a lot of folks are hesitant to tear into gears,usually if you go easy and use basic skill you can tackle these yourself and save a lot of $$. In this case the bearings a less the an quarter of the cost of a new gearbox.

[richhiway]

 

 

This is a very handy little tool for removing and installing snap rings. Especially the larger stiffer ones.
The parts came and I am going to reassemble the gear box.

[richhiway]

 

 
Make sure you clean all the parts well. Of course reassembly is the reverse of assembly. Make sure you take note of the location and thickness of any shims. In this gearbox the bearings are shimmed to set the depth of the gear mesh. In this picture the rear bearing is on the shaft and then tapped into the case. Next will be the front bearing ,retaining clip and seal.

[richhiway]

 

 
Most of the time on this type of equipment the bearing not a "press" fit but an "interference" fit. So instead of needing to use a press you can just tap the parts together. When using a drift make sure it has a large square end. Tap the bearing from side to side,easy and evenly and it will go right into the housing. Don't force anything, if it doesn't go. Only strike the bearing on the race you are installing. In the picture the inner race is going over the shaft and the outer race is being driven into the case. So do not strike the inner race when driving the outer race into the case as the force would be transferred through the roller bearings. This could damage the bearings or inner races.

[richhiway]

 

 

This lower bearing is a tight fit on the shaft and the bearing needs to be driven into the case. I heated the inner race with a heat gun,expanding it so it slid onto the shaft with ease. You can also put the opposing part in the freezer or in dry ice. This will allow tight fitting bearings or bushings to slide together with ease.

[richhiway]

 

 
Back to where we started. It was a lack of lubrication because of a bad seal that allowed condensation to rust the bearings. Always use high quality lubricants and change them as recommended. This is a mower so it will only be used in warmer weather so the 140 gear lube is a good choice. A mower is subject to shock loads and the thicker oil will maintain a cushion between the gears at higher temps. Equipment that will be used in cold weather can suffer from lack of lubrication from too thick(higher viscosity) an oil. A 85W 90 synthetic would be a better year round choice.

[richhiway]

 

 
Also use high quality sealants.You don't want a leak to ruin all your good work. After the cover was installed, I reassembled the gearbox to the mower with a new belt. Everything worked great and I mowed the lawn before the rain tomorrow.