In 1958, the first prototype of the T195 self-propelled howitzer was completed but a number of failures occurred in the torsion-bar suspension. The prototype differed from later vehicles in that it had a different shaped hull and turret, the seventh roadwheel acted as the idler and the short-barrelled 105 mm howitzer was fitted with a muzzle brake.

In 1959, a policy was established that diesel rather than petrol engines would be used for future vehicles and the prototype of the T195, which was powered by a Continental petrol engine, was refitted with a Detroit diesel engine and called the T195E1. Trials with the latter were carried out in 1960 but there were failures of critical suspension and final drive components. These deficiencies were subsequently corrected and, in December 1961, the T195E1 was classified for limited production as the howitzer, light, self-propelled, 105 mm, M108.

Production of the M108 was undertaken by the Cadillac Motor Car Division of the General Motors Corporation: the first production vehicle was completed in October 1962 and production continued until 1963. The vehicle was in production for only a short period, as the US Army decided to concentrate on the self-propelled 155 mm M109 rather than the 105 mm M108. The M108 is almost identical to the M109, and differs only in its armament, loading system, fire-control system, ammunition stowage racks and in that it is not fitted with spades at the rear of the hull. In the case of the M109 these were deployed one either side at the rear to provide a more stable firing platform.

The 105 mm M108 self-propelled howitzer has a crew of five: the commander, gunner, two ammunition numbers and the driver. The hull is made of all-welded aluminium armour with the driver at the front of the hull on the left, the power pack to the right and the fighting compartment at the rear. The aluminium armour provides the occupants with protection from small arms fire and shell splinters.

The driver has a single-piece hatch cover that opens to the left, in front of which are three M45 day periscopes that can be covered by small metal flaps to prevent damage. The centre day periscope can be replaced by a passive periscope for driving at night.

The Detroit Diesel Model 8V-71T engine is coupled to the Allison Transmission XTG-411-2A cross-drive automatic transmission, which is at the front of the hull.

The all-welded aluminium turret is at the rear of the hull. It has a square hatch in each side that opens to the rear and twin doors in the rear. The commander is seated on the right and has a cupola which can be traversed manually through 360°, a single-piece hatch cover that opens to the rear and an M27 day periscope. Pintle mounted on the forward part of the commander's cupola is a .50 (12.7 mm) M2 HB machine gun. The gunner is seated on the left side of the turret and has a square single-piece hatch cover that opens to the right. Twin doors are provided at the rear of the hull for ammunition resupply.

The torsion bar suspension either side consists of seven dual rubber-tyred road wheels with the drive sprocket at the front and the idler at the rear. There are no track-return rollers. The tracks are of the single-pin, centre guide type with replaceable rubber pads.

The M108 is fitted with night vision equipment but no NBC equipment. The basic vehicle can ford to a depth of 1.828 m without preparation.

Main armament is an M103 105 mm howitzer in an M139 mount. The recoil system is of the hydrospring, constant retarding force type while the breech block is of the sliding wedge drop block type. The weapon has an elevation of +74°, depression of -4° and 360° turret traverse. Gun elevation/depression and turret traverse are manual. Normal rate of fire is 1 rd/min, but 3 rds/min can be fired for short periods. Fire-control equipment consists of an M15 elevation quadrant, an M117 panoramic telescope with a magnification of ×4 and a 10° field of view, and an M118 elbow telescope with a magnification of ×4 and a 10° field of view.

The following types of ammunition can be fired:

• HE (M1) with the complete round weighing 18.107 kg, a maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HE (M444) (carries 18 M39 grenades) with the complete round weighing 19.05 kg, a maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• HE (M413) (carries 18 M35 grenades) with the complete round weighing 19.05 kg, a maximum muzzle velocity of 494 m/s and a maximum range of 11,500 m

• HEP-T (M327) with the complete round weighing 15.17 kg, a maximum muzzle velocity of 559 m/s and a maximum range of 8,685 m

• HERA (M548) with the complete round weighing 17.46 kg, a maximum muzzle velocity of 548 m/s and a maximum range of 15,000 m

• Illuminating (M314 series) with the complete round weighing 21.06 kg, a maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• Illuminating (M314A3) with the complete round weighing 21.06 kg, a maximum muzzle velocity of 494 m/s and a maximum range of 11,500 m

• Leaflet (M84B1) with the complete round weighing 18 kg, a maximum muzzle velocity of 433 m/s and a maximum range (charge 7) of 9,091 m

• Smoke (M60 series) with the complete round weighing 19.46 kg, a maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• Smoke (M84) with the complete round weighing 19.03 kg, a maximum muzzle velocity of 494 m/s and a maximum range (charge 7) of 11,500 m

• Belgian Army M108A2B training vehicles

The Belgian Army modified at least 14 M108 105 mm self-propelled howitzers by mounting these turrets on surplus M109A2 hulls. This is designated the M108A2B and is used for training purposes as 105 mm ammunition is cheaper than 155 mm ammunition.

• Belgian Army VBCL fire direction and command post

The Belgian Arsenal du Materiel Mecanique et de l'Armement at Rocourt converted a total of 45 surplus M108 chassis into the VBCL (Vehicule Blindéde Commandement et de Liaison) with final deliveries being made in 1994.

The VBCL is a fire direction centre and command post for Belgian Army field artillery battalions and batteries. It is fitted with four BAMS radios, two telescopic antennas PU-8, a 2.7 kW generator DE-CA, tent to increase working area, ABM-1045 field telephone system and a roof mounted .50 (12.7 mm) M2 HB machine gun.

The Fire Direction Centres are fitted with ruggedised portable computers PCI but are otherwise similar to the CP versions.

• Austrian Army fire direction and command post vehicles

These are similar to the Belgian vehicles but are based on an M109 155 mm self-propelled system, rather than an M108.