853 gear reduction mayhem

[Old_853]

I had this weird popping noise under heavy load, but only when turning one direction. Figured it was the chains, which are worn. Turns out the input shaft bearings came apart in the gear reduction, taking out both the small and big gear along the way. It still worked fine. Big gear is about a grand on bobcat. Little gear input shaft part number 6558271 is no longer available. I have scoured the depths of ebay, every spare part site I can think of looking for that or the whole gear reduction case part number 6708266 as well. Lots of them for the smaller machines. Zero for the 853. Any ideas? I've considered building the teeth up with the welder and grinding, but I know it wouldn't be as strong.

 

[wateka]

I found this guy on Craigslist because he's near me in Texas. He says he has one - give him a call

 

[Old_853]

I found this guy on Craigslist because he's near me in Texas. He says he has one - give him a call View attachment 6108

That's awesome, thank you! I just sent him a message. Kind of early to call on a Sunday. Hopefully he's willing to ship it to Wyoming.

Edit: He's shipping it out in the morning. Thanks again, I was ready to weld and grind every tooth.

 

[Old_853]

Got both rebuilt and back in. I had to pull the drive gear on the left side to get it back in there. I don't remember how I got it out, but it's pretty tight even with the gear removed. Both left and right sides had gnarfed gears, as well as the craigslist find. Must be why bobcat got away from the design and parts are unobtanium. I cobbled together the least borked sets out of three, and might try to weld and recut the spare set if/when the current ones grenade. I tried ordering the primary shaft from a 743. Close, but no cigar. Everything is the same except the drive motor input. It may be possible to swap drive guts with a 743 motor into an 853, but the shaft is much smaller. The large secondary gear is the same part number between the two. The 743 takes 80 series chain, and the 853 takes 100HS chain, so you can't swap the entire gear box easily. Eh. I think the easiest thing would be to delete the entire gear box and fit a more modern drive unit, although you would lose brakes without some hillbilly engineering. Also did axle bearings and seals, and rebuilt the drive motors while I was in there. Next is bushings all around for the bobtach/rams. The neverending project.

 

[Old_853]

Hydraulic fluid leaking into chain case when running. Why? Greased seal lips, no nicks or burrs. Chaincase drain hose is clear, blew air through both side to be sure. Chain case drain ports in motors clear. Can blow air through the two pin holes in the drive shaft. No obvious issues. Order new seals again and say a prayer? I don't know what else to do.

 

[wateka]

My thought is a torn seal during reassembly? I say that because of this:

https://www.skidsteerforum.com/threads/hydraulic-leak-into-chain-case-on-463.118540/post-124680

 

[Old_853]

Just put everything back together and put in 4 gallons of fluid and let it sit awhile. Without it running. The chaincase level increased. That means it has to be Oil Seal 6513588. Ordered two. I'm going to try to find a seal driver. I installed these ones with a brass hammer and thought I was careful, but that was on the bench. Installing them in the hull will be a good time.

 

[Mitch500]

Just put everything back together and put in 4 gallons of fluid and let it sit awhile. Without it running. The chaincase level increased. That means it has to be Oil Seal 6513588. Ordered two. I'm going to try to find a seal driver. I installed these ones with a brass hammer and thought I was careful, but that was on the bench. Installing them in the hull will be a good time.

That seal head me worried when re installing the drive motor. I should check my hydraulic reservoir and also chain case level as well.