Bobcat Drive Motor Rebuild, teardown for inspection, failure analysis. 

Thanks 👍

Dead center of carrier shaft is a plug that if loose will allow oil to bypass into chain case. When you pull the motor you will see what I'm talking about. Probably the most overlooked item when you have oil pumping in to the chain case.

I promised an update so here it is. We put new seal kits in both drive motors from Loader Parts Source (nice people). Removed all the inline filters on the case drain lines (will replace) and checked for good oil flow. Tighten the center screws on both sides but unsure if they were lose or not. We also had Bobcat of Columbia (also nice guys) replace both carrier seals. One of them failed and they just hammered them in with a tool (basically a piece of pipe). The small spring around the seal had fallen off when we inspected them. Here's a suggestion - we wrapped tape around a 2" PVC sewer pipe until it expanded the seal to allow it to slide over the shaft. That seems much better than beating on a new seal. We couldn't get it by hand but it was cold that day. We are driving around with the chain case cover off and looking down at the drive sprockets. We pulled the chain case plug (25 gallons of hydraulic fluid in it) and are watching for leaks. 15 minutes of running around and we are going to button it back up. I don't have a warm and fuzzy feeling but it's not leaking yet.

@@tetradgroup I've got a 843 that is putting oil in the chain case but the drive motors feel strong, think that plug is probably the issue?

One more post a year later. We never resolved this and used it with low power over the Summer. We've now pulled the engine/pump + both drive motors and ran it outside of the machine. We added ball valves and gauges so that we could see pressure on all four lines from the drive pump. We also split the hydrostatic pumps apart and looked for damaged (in good shape we believe no gouges or scratches at all). The problem looks like a blow seal on a wear plate in one of the drive motors. It gushes oil under pressure and that would explain the loss of drive power. A kit is ordered and I'll follow up. Also working on a RU-vid post to share.

Thank you so much! I don't have any videos on the excavator drive sections yet but thanks for the idea.

Absolutely, it can leak into the chain case thru carrier shaft seal. Also check the center of the carrier for a small plug, make sure it is tight and sealed properly. Easy job and should probably do both sides while you are in there. Just remove the drive motor and you will see the shaft seal, pop it out and install new seal.

Yes, it needs to be timed correctly. It's super easy to do with a service manual.

Yep, the ol' self diagnosis, has to be the drive motor. At least we know what's not the problem 🙂

Concrete mixing tubs from Home Depot

@@tetradgroup thanks!

Motor carrier seals and possibly bearings. Usually it's just the seals

And how did you check what side it is bad? Sorry, so many questions i know 😅but we dont have any mechanics around

www.4tetradgroup.com

This was a local customer and knew I rebuilt hydrostatic motors, everyone else is weeks out before they can even look at it.

@@tetradgroupGreat detailed teardown of every part in that motor another excellent video

Thank you so much!

Thank you so much!