Just got a late 70's 520 Bobcat repowered with a Predator 670. Where do I get good info on these things?

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Wadeofdesth

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Joined
Aug 31, 2022
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I've downloaded the service manual but can't find a hose schematic, any leads?
Also, shes got some axle leakage. I've found the seals and bearings for cheap enough but all of the how to videos are for newer machines. How difficult is that and what special tools should I have and how do I know if I need to do the bearings as well (or do you just kinda always do both while you're at it)? I'm a carpenter/contractor by trade and a somewhat adept shade tree mechanic for what it's worth. Thanks in advance!
 

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brdgbldr

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Go to this site:
and enter your model or serial number.
It is the parts catalog. It will show you exploded view of all the pats on the machine.

On the older machines you could do the front axles since the access panel is accessible. The rear access panel is normally only accessible if you remove the pump or drop the chain case.

There used to be some good photos on here of replacing the seals and bearings on older machines. Mainly 743's. Not sure where these ended up. I guess they must have removed them at some point.

I did a 742 years ago and found it easiest to remove the chain case from the frame for access to all the axles. There was a frame bolt that was hard to get to, on both sides, but someone in the past had cut an access hole to get to them.

I also made a tool that was a steel bar that I could bolt to two of the lugs with a large nut welded to it in the center. This can be used to keep the axle from turning while trying to get the bolt out, and into, the axle. I actually put a box wrench on the axle bolt and wedged it against the chain case and then used a socket on my home made tool to turn the axle. This tool also makes it easier to get to the main link on the chains that will need to be removed and reinstalled.

There are washers/shims that Bobcat sells to take out any play in the axels, not cheap. They are "shaved" where the axle meets them to different depths on each side so one of them accommodates two different thicknesses if that makes sense.

The axle bolts on my 742 were torqued to 600 ft/lbs. When I used a pry bar, as suggested by people, instead of a torque wrench, I ended up stretching the bolt. Luckily it didn't snap off in the axle. I had to buy a new bolt and a torque wrench.

Seals and bearing are pretty standard. I would suggest replacing the bearings while you have the axles out. They are cheap and not very hard to replace. Also, make sure to use seal savers on the axles if there is a groove worn in the axle from the old seals. You can get away without any special tools for bearings and seals but it takes more time.
 

DaewooWho

New member
Joined
Sep 4, 2022
Messages
2
I've downloaded the service manual but can't find a hose schematic, any leads?
Also, shes got some axle leakage. I've found the seals and bearings for cheap enough but all of the how to videos are for newer machines. How difficult is that and what special tools should I have and how do I know if I need to do the bearings as well (or do you just kinda always do both while you're at it)? I'm a carpenter/contractor by trade and a somewhat adept shade tree mechanic for what it's worth. Thanks in advance!
I ran similar Bobcat. The love joy coupler from engine to pump was a weak point. Needed replacement often.
 
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Wadeofdesth

Wadeofdesth

Member
Joined
Aug 31, 2022
Messages
15
T
Go to this site:
and enter your model or serial number.
It is the parts catalog. It will show you exploded view of all the pats on the machine.

On the older machines you could do the front axles since the access panel is accessible. The rear access panel is normally only accessible if you remove the pump or drop the chain case.

There used to be some good photos on here of replacing the seals and bearings on older machines. Mainly 743's. Not sure where these ended up. I guess they must have removed them at some point.

I did a 742 years ago and found it easiest to remove the chain case from the frame for access to all the axles. There was a frame bolt that was hard to get to, on both sides, but someone in the past had cut an access hole to get to them.

I also made a tool that was a steel bar that I could bolt to two of the lugs with a large nut welded to it in the center. This can be used to keep the axle from turning while trying to get the bolt out, and into, the axle. I actually put a box wrench on the axle bolt and wedged it against the chain case and then used a socket on my home made tool to turn the axle. This tool also makes it easier to get to the main link on the chains that will need to be removed and reinstalled.

There are washers/shims that Bobcat sells to take out any play in the axels, not cheap. They are "shaved" where the axle meets them to different depths on each side so one of them accommodates two different thicknesses if that makes sense.

The axle bolts on my 742 were torqued to 600 ft/lbs. When I used a pry bar, as suggested by people, instead of a torque wrench, I ended up stretching the bolt. Luckily it didn't snap off in the axle. I had to buy a new bolt and a torque wrench.

Seals and bearing are pretty standard. I would suggest replacing the bearings while you have the axles out. They are cheap and not very hard to replace. Also, make sure to use seal savers on the axles if there is a groove worn in the axle from the old seals. You can get away without any special tools for bearings and seals but it takes more time.
Thanks for the incredibly detailed response! I'll let you know how it goes when I get to it. I'm guessing I'll have a few questions...
 

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