HEMTT entered service in 1985. Currently the product-improved
HEMTT A2s is in production, with A4 upgrades taking effect in
July this year. The most recent improvements to the HEMTT A2
are a fully air conditioned cab and cab structural changes that
makes installation of add-on-armor in the field quicker and
easier. HEMTT is providing the baseline for the U.S. Army 'Family
of Heavy Tactical Vehicles' (FHTV). With payload capacity of
13-ton and off-road capabilities, HEMTT makes the backbone of
the U.S. Army’s logistics fleet.

A2 is the HEMTT version currently in production. According
to the production plans, the more powerful, better protected
A4 (insert) will enter production in July 2008. (Photos: Oshkosh)
HEMTT A4 is powered by a 500-HP Caterpillar C-15 engine.
This engine provides 55hp more than the original engine used
in the HEMTT. The engine is coupled with an Allison 4500 SP/5-speed
automatic transmission, rated for 600hp. This powertrain offers
a 1750-lb. torque, gross input, and handles more power and
torque for the engine upgrade without changing gear ratios.
Survivability and self-protection features are introduced
with the standard version. The vehicle is provided with basic
armor protection including an Integrated under cab protection,
making part of the A-kit, and attachments for add-on B-kit
armor, complying with the Army's Long Term Armor Strategy.
The vehicle is also fitted with an integrated mounting for
a protected gunner position (GPK) and machine-gun mount on
the cab roof.
HEMTT A4 will be produced in several models, including the
M997A4 cargo truck, the M-978A4 fuel servicing truck (tanker),
the M1120A4 load handling system variant, M-982 A4 and M-983
A4 tractors, and M-984 A4 recovery truck fitted with cranes
and winches.