I still have my 6635SXT series 2. I thought they were built a little earlier and changed to the 6640 in 2003, but limited info found as well. My 6635 has the 80hp turbo Diesel Deutz...strong engine! I found the dirt in the belly was due to the skid-plate edge opening. Worked like a shovel when dragging the belly on piles of dirt. Had 2 leaking hoses that caused the oil-spill and the dire was saturated. a little bending on the skid-plate once removed and all fixed now. Watch it though, the dirt packed near the nose & I have some small rust/rot now from the moisture poking through. I picked up 2 railroad ties (wood) which are like 12" x 12" that I drive up on. Raises it high enough to remove skid plate and access underside easily. Makes oil-changes clean & easy and no risk of it falling off jack-stands etc. Use the bucket to raise the front wheels and drive right up. Not long after I got it, all the hydraulics quit out in the field. Had to fix it in that spot (can't tow these 8000lb monsters easily w/o removing the drive-chains). After much digging and little answers to be found on the forums, I pulled the hyd-pump and found no problem. So..pulled the tandem pumps & found a small shaft coupler had the splines stripped out of it. Would not let the engine spin the pump shaft. A $14 coupler and 3 hr's later it was back running. I did have to drain the hydraulic oil to do this, but found baggies and zip-ties can keep the hoses from leaking in the shoft-term. I also changed the Timing belt since it has 2000 hr's on it. Read it's better to change for $100 than bend a valve. Was messy, but not difficult if you purchase the kits available on Ebay. I found some of my tools are not big enough for hoses etc, otherwise just takes time to do. Mine is a 99 according to the engine plate. It has the Gehl "T" handles on left/right for control. Only foot control is for the optional hydraulic attachments (mine is SXT, 2-speed not high-flow). My only disappointment was the loop-hook- pin Gehl ALLTACH attach for the bucket/forks. Being older, cannot find any attachments to fit unless Gehl specific. I found on Craiglist the Gehl QUICKTACH which is basically a Bobcat plate that Gehl did sell at the time as an option. Now I can use Bobcat attachments and can rent other attachments that are available these days if needed. The XX35 manuals (both operator & service) are available online for FREE if you do some digging. I have found most of my parts online (new) from German Bliss, Golden Eagle, Ebay and others. Use the service manual to reference the part number and do a search. I found it's not that difficult to work on, but some areas are tight access and lots of contortion and bending to get to the areas. A board laying across the front with the cab tilted helps. Good luck w/yours....Scott