We may have found other answers which could help you.
Click here for Turning Belt Fine
How to fix idler clamp assembly (hardwood/carpet switch) on Eureka SmartVac?
Eureka Boss Smart Vac Thermal Cutoff ?
Eureka 4870 vacuum?
How do I remove the canister motor 116.21514?
eureka 4870B smartboss, upright vaccum?
Eureka Model 4870 Motor Replacement?