This is the response that I received from Tuff Torq...
John Deere does not buy the K92. They buy the K91 which is a little different and has a few parts that are different from the K91. But I do not really know what you are referring to in your email. If it is the valves on the center case the different ones are for different applications. So I am wondering what you are meaning.
Thank you for your inquiry, today. Do not hesitate to contact us if you have any further questions.
Tuff Torq Corporation
After Market Service Parts
6041 Hunter Road
Talbott, TN 37877
Phone (866) 572-3441
Fax (423) 317-2312
Here is my response back to them...
I apologize for the mistake. The 2006-2012 X Series tractors used the TT K92 according to my research.
When adding a John Deere Model 45 FEL to one of their older X Series lawn & garden tractors the instructions recommend that a Transaxle Hydrostatic Pressure Relief Valve (THRV) replace the OEM Forward Free Wheeling Valve in the K92. The John Deere part number is BW15043 for a 2WD tractor and a BW15044 for a 4WD. These THRV's are taller than the OEM valve and require a different Free Wheeling Lever be used to allow the tractor to roll when not running. Apparently the K92 achieved “relief” by tire spin that can sometimes be compromised with extra ballast and other weight when using a Front End Loader.
I am trading a 2008 X700 2WD tractor for a 2012 X728 4WD and wanted to know if it would be a problem to use the BW15043 THRV in the 4WD X728 as I am having trouble locating a BW15044 that is made specifically for the 4WD tractor.