Transmission slip

I've got an old Cat 621 scraper with a transmission issue I can't figure out. If anyone knows these transmissions, would you mind giving me a call? I'd really appreciate the help. 4064502325

You'll have better luck if you describe what's going wrong. Nobody's going to call without knowing what the issue actually is.

Could that actually be a 623 instead of a 621? The transmission might be different on that model.