Technical When to change clutch disc

How do you know when to change a clutch disc. Its it mileage or a feel?

 

Mostly by feel, I'd say. And sometimes even by smell . . . If it's slipping bad enough!

 

We ( Pop's ) used a '65 Chevelle wagon/ 410 rear 3/tree. I'd say mostly light hauling.
Myself I would be trying to bust that 283 at any chance. ( only once a failed rocker arm )
When we quit the biz ( 'bout 90,000mi., it went to Mom to use it a couple years then handed over to my sister ( devout automatic user ) who had her husband take it for his daily use.
Ten years back and forth it was p***ed around even back to me winning occasional stop light drag challenges. At 140,000 Dad retired the old wagon ( I need a tissue), with the original clutch.

 

When I couldn't shift into any gear without grinding. Got one going right now that the springs in the Long style pressure plate broke.

 

Set the parking brake and try to start off like you normally would, it should stall quickly.

Phil

 

Depending on the use it has had, it would be wise to look at the flywheel surface.
If you see wavy ( feel for ridges ) surface and blueing, take it off for a trip to your local friendly machine shop for further inspection and resurfacing. Around here the go to guys are NAPA.

 

Last time I changed one it was because it was slipping when I shifted into second gear rather agrressively. Two years later it's still working well. I did change one once because most of it was left back on the road.