Grinding noise in Toro self-propel system

I have a Toro Electric Start Recycler Mower with the Personal Pace self-propel system. It's about a year and a half old. About 90% of the time when you start it in motion, or going up a grade, there is a grinding noise coming from the rear wheels. At least it sounds like that's where it's coming from. Once the mower is moving on the level, there is no noise. Anybody have any idea what could be the cause of this??
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Is it belt or shaft drive?.....sounds like somethin's slipping
If the rear wheels are geared you may have dirt or grass in the casings..... can you clean 'em out? don't use any lube or you'll just attract more dirt.
Has it been doing it all the time since new, or did it just start?
Check http://www.toro.com/home/mowers/recycler/index.html
tomkanpa wrote:

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