Tanks in the Antarctic: Unidentified US light tank?

Status Report has an interesting article about three M2A2 light tanks sent to the Antarctic in 1939 as part of an expedition.  Russian tank researcher Yuri Pasholok was able to find a Soviet report about the expedition in the Russian archives detailing some of the technical issues encountered with the light tanks in the rather harsh climate of the Antarctic.  These details are translated and available over at the Archive Awareness blog for those that are interested.  The Status Report article can be read here.  Pictures of the rusting M2A2 tanks can be found on the photography websites of Kevin Raber and Martin Grace.

Kevin Raber Pictures: Tanks in Snow, Antarctica ,Tanks and Ice , Rusty Tank treads and gears, Antarctica

Martin Grace Picture Gallery here

The photos by Martin Grace reveal that while one of the vehicles is an M2A2 as stated in the Status Report article, the other vehicle is not.  

It is clear from the photos that one of the vehicles does not have the radial engine of the the M2 series of light tanks, it appears to have in inline engine.  Also, it has a long suspension arm going to the rear idler that is not present on M2 light tanks.  The suspension appears to resemble that of the 1936 T3 light tank.  Hunnicutt’s “Stuart: A History of the American Light Tank” describes the T3 as being powered by a standard Ford V-8 automobile engine.  The picture Hunnicutt provides of the T3 does not feature the suspension support arm to the rear idler found in the Martin photo.  Hunnicutt mentions that there was a second model created called the T3E1 which was fitted with a volute spring suspension and a Menasco air-cooled engine.  Hunnicutt further states that the T3E1 prototype was converted into the cross country carrier T5.  Unfortunately, he does not provide pictures for either the T3E1 or the T5 carrier. Could this vehicle stranded up in the Antarctic be the T5?

T3 light tank as pictured in Hunnicutt book

Suspension of unidentified Antarctic tank by Martin Grace

Engine of unidentified Antarctic tank by Martin Grace

Edit: Over at the AFV Discussion Board, Chris_C pointed out that there is a picture of the T5 in the book US Military Tracked Vehicles by Fred W.  Crismon.  Here is the picture.

Edit #2: We have a definite answer! the vehicle in question is a T3E4 Tractor. Here is an image of it.  Thanks to the crew at the AFV Discussion board for the info.