charles raymond

I'm having the same problem. I tried a new mulching blade for the HU775L model, but this didn't help! Make sure you have the "claw" on the blade facing up towards the mower deck. My mower was serviced under warranty and the blade was incorrectly reinstalled and the belt was stretched due to the svc ctr installing belt around the belt guide. The manual indicates to replace the drive belt, but good luck trying to find a replacement part for the belt. The only # I was able to come up with was at Sears.com that cross referenced the belt #532421527 to their # 421527. I'm planning to try this belt and if problem still occurs, I'm returning the mower.