My 3 year old Craftsman GT5000 lawn mower jerks and/or surges while in motion. Is this a problem with the drive-belt? If so, would I be able to make adjustments to tighten it or will I need to purchase a new belt? Or, is it something completely different? Thanks.

Check the belt for damage.

Thanks Mowerman. Being new to this site I am not sure if this is how I respond but here goes. I looked the belt over and see no visible damage (cracks, cuts, dry rot, etc) I am not sure if this is supposed to be tightened to the 1/2"-3/4" deflection. Do you know off hand if there is a mechanism to tighten it and if so where I might find it on the mower? Thanks

Well I ended up figuring this out myself. Although it never made a noise and the oil level was good, it turns out it is the final drive gear pinion (gear) in the transaxle. The teeth in the center of the gear were completely gone. After seeing that Sears wanted $897.00 for a new transaxle I decided to open it up myself. Although it is time consuming to remove the transaxle it is definitely worth it. After identifying the bad pinion I went online with Sears.com and including shipping it was less than $25.00.

My 3 year old Craftsman GT5000 lawn mower jerks and/or surges while in motion. Is this a problem with the drive-belt? If so, would I be able to make adjustments to tighten it or will I need to purchase a new belt? Or, is it something completely different? Thanks.
I had this exact problem with a Craftsman 24 HP riding mower that I inherited with my home. It's about 15 years old. I bought a carb rebuild kit from a local parts house (about $10), and in about an hour was good has new - not a big job. Buy a can of spray carb cleaner. No more surges. Just replaced the deck and plan on using this mower for another 15 years.