I have an older Spirit (Murray) 8 HP 25" snowblower (model B2580-020), and I'm having issues with the drive system (not the auger). I'm guessing this machine is somewhere around 15 years old. I have 6 forward speeds and 2 reverse. I have a driveway with an incline (not massive, but definitily not flat). When I drive the snowblower around in the garage (level), all the gears work fine. When I drive it up the driveway, most of the high gears won't drive. If I'm blowing snow, I have to have it in 1st gear, and push! It's almost as though the belt is slipping. I pulled the cover off to look at the belts, and the drive belt looks fairly new. Someone told me about "friction plates" that could be bad. The problem is, I can't find any documentation on this machine to know what to look for. Most part dealers can't even find my machine by the model number. Should I replace the drive belt? Is there any kind of drive belt adjustment? Any other advice?