620 Reverse issue

[G-NEST]

Hi all, Earlier this summer I picked up a older 620 after going though the fluids and ignition it’s been a great machine to have around the yard. Recently I’ve ran into an issue and having trouble finding a solution, so I am hoping someone might be able to help guide me in the right direction. The issue: Intermittently the left drive will lock up in reverse. It feels like something is binding, typically I can get past the issue by rocking it forward a bit. It really feels like a chain issue but I don’t know what I’m looking for. I took off the chain cover, and found my chains to be very loose per specs of the service manual. I tightened them back to spec and went ahead and did the right side as well. Unfortunately this didn’t resolve my issue. Looking at the primary and secondary chain and sprockets everything looked pretty good, the final drive is very hard to see but nothing looked amiss in the chain. Any pointers in where to start looking?

 

[G-NEST]

Here’s a video of what’s going on. I started the video in forward and then switched to reverse. I can go in forward all day long then as soon as I switch to reverse it locks up. It appears the drive motor is still trying to spin but something else is binding. While messing around (not in video) I heard a slide and a clank. And then had reverse again. Like a bearing/sprocket slid back in place, then had reverse again. I’m just looking for pointers on what you would do next. Do I drain it, take off the chains and start with a flash light down in there? Is there anything else I should try to wiggle or inspect before I do this? https://youtu.be/Z48ZnCuFlYw Thank you for reading!

 

[Tazza]

Here’s a video of what’s going on. I started the video in forward and then switched to reverse. I can go in forward all day long then as soon as I switch to reverse it locks up. It appears the drive motor is still trying to spin but something else is binding. While messing around (not in video) I heard a slide and a clank. And then had reverse again. Like a bearing/sprocket slid back in place, then had reverse again. I’m just looking for pointers on what you would do next. Do I drain it, take off the chains and start with a flash light down in there? Is there anything else I should try to wiggle or inspect before I do this? https://youtu.be/Z48ZnCuFlYw Thank you for reading!

I see what you mean, something is sticking, it's not the brake is it? some how binding up causing it?
I don't know enough about this model to really say for sure what it could be

 

[G-NEST]

I see what you mean, something is sticking, it's not the brake is it? some how binding up causing it?
I don't know enough about this model to really say for sure what it could be

Thank you for the reply, From what I’ve seen in the manual I think brakes are optional on this model and mine doesn’t have them. I figured I’d check in with you guys before I start tearing in. Hopefully will get some shop time in, over the next couple days. I’ll update with what I find, and possibly come back with more questions ????

 

[G-NEST]

I see what you mean, something is sticking, it's not the brake is it? some how binding up causing it?
I don't know enough about this model to really say for sure what it could be

I finally got out there tonight. It appears that when a wheel bearing was replaced by the prior owner they never put the two inch axle nut/sleeve/retainer back on. Nonetheless I found a large nut wedging up against the final drive chain. When moving forward it was fine but it would catch in reverse. I’ll need to take the hub out and reassemble it properly. Thanks for the help.

 

[Tazza]

I finally got out there tonight. It appears that when a wheel bearing was replaced by the prior owner they never put the two inch axle nut/sleeve/retainer back on. Nonetheless I found a large nut wedging up against the final drive chain. When moving forward it was fine but it would catch in reverse. I’ll need to take the hub out and reassemble it properly. Thanks for the help.

Something so stupid, but glad you found it before it caused damage.