old whirlpool dryer

Model Number: LE5800XSN3
Brand: Whirlpool
Age: More than 10 years

The hi temp fuse started blowing after 20 years. I have replaced it and the operating temp sensor that came in the kit. I bought the vent cleaner tool and cleaned the 22 foot vent. It is clear. I have thoroughly cleaned the machine and have good airflow from the machine and through the 22 foot vent. When I run the dryer with the flexible hose draped over the machine into the garage it works fine. But when I connect the hose to the 22 foot vent it overheats. The vent is clean. It's driving me nuts. Can anyone help before I buy a new dryer?