Warriorking,
Here's the link where you can get a center differential:
http://www.hobbypeople.net/gallery/149794.asp
About the center diff, it would be a good idea to buy it for preventing damage to the gears if you're jumping, however, I have these (
http://dadders.net/braces-mammothst.htm), they are Dadders chassis braces and that will totally prevent any chassis flex, along with support for the transimission. I would suggest getting the 7075 for decreased weight, with Dadders baces, and a center diff. The link for the 7075 chassis is also at Hobbypeople:
http://www.hobbypeople.net/gallery/149878.asp If you have any further questions lemme know, I won't be able to run my ST for a little bit because I broke my hinge pin retainer, I would also consider this upgrade too:
http://rcvisions.net/HingePinRetainers.html They really help out along with aluminum arms from Big Air:
http://bigairproducts.com/
Check out My Models to see my ST, there will be a Hitec 5955TG servo added, along with the RC Visions hinge pin retainers. Good luck and feel free to ask questions! [8D]