Geof- this is great additional info on the program, I was having a hard time figuring out how this all came together. Thank you!Yes, very interesting.
I think that this chassis was originally assembled at STEWART STEVENSON. For a short time they worked with TATRA to develop a independent suspension chassis retrofit. It could be an early NATC assembled chassis, but I am not aware that NATC ever assembled a vehicle with an ALLISON transmission. I have two of the STEWART STEVENSON chassis here.
Much of the M939/TATRA development and testing was done at NATC (Nevada Automotive Test Center) near Silver Springs, Nevada for the USMC MTTR (Medium-Tactical-Truck-Replacement) program. This was an effort to retrofit a M939 chassis over a 6X6 TATRA chassis. There were no other independent suspensions available in the US at this time. I have extensive information on this swap if you have an interest. ISLAND CITY ENGINEERING beginning in 2005 made a similar swap placing a FMTV 6X6 upper chassis over a TATRA 6X6 chassis. The Marines eventually built a new vehicle, the MTVR (Medium-Tactical-Truck-Replacement) rather than reset M939's. It is interesting that the MTTR program at NATC is in reality the foundation program for all US independent suspensions that followed including OSHKOSH. It is also the case that the OSHKOSH and other US developed independent suspension performance is all fundamentally based on TATRA truck performance as the performance specification for the 7-ton MTVR is based largely on NATC MTTR TATRA performance testing. To their credit TATRA and NATC set a high bar. NATC assistance led the USMC to early high-mobility vehicle success compared to US Army efforts.
Twin Disc developed an innovative transmission for the MTTR. The TD drop-box transmission is sandwiched in the TATRA frame to become a frame structural component similar to the TATRA transfer case installed in your truck.
The USMC contacted OSHKOSH during the MTTR program to ask what OSHKOSH TRUCK could offer. This was the beginning of the OSHKOSH independent suspension program that evolved entirely within the OSHKOSH T&D Lab. The OSHKOSH dual control arm suspension was originally developed as competition for the USMC TATRA MTTR program.
US ARMY TACOM at the time held that independent suspensions were unnecessary as the Army attempted to justify the struggling FMTV program. FMTV mobility is miserable and OSHKOSH is presently contracted by the Army to retrofit an independent under the FMTV system.
View attachment 850220View attachment 850221View attachment 850222View attachment 850223TATRA's stiff central tube frame makes it excellent for reset programs. All wheel forces are resolved in the tube frame assembly. The cargo frame simply supports the load. This why TATRA can use an entirely welded cargo frame over the central tube. This is not possible with a ladder frame trucks as the frame torsional forces result in rapid weld fatigue and failure.