In October 1942 it was decided to investigate the possibility of adapting the 90mm AA gun as a high velocity anti-tank gun for mounting in American tanks and SP vehicles. In early 1943 a trial installation of a 90mm gun was made in the turret of the M10, but the gun proved too long and heavy for the turret which was, in any case, not entirely adequate for the 3in gun. In March 1943, therefore, work began on designing a new large turret to fit the M10 and take the 90mm gun. Tested at APG, the modified vehicle was very satisfactory and an initial “limited procurement” order of 500 vehicles was placed under the designation T71 GMC. In June 1944, the vehicle was standardised as the M36 GMC and entered service in NW Europe in late 1944 where it proved a most successful type able to knock out the heavy German Panther and Tiger tanks at long range. Some tank destroyer battalions notched up impressive scores with little loss to themselves using the M36. A priority programme to provide more M36 type vehicles to replace the less satisfactory M10 led to the following variants:
M36: Initial production type based on M10A1 chassis which was in turn based on M4A3 medium tank chassis. 300 produced by Grand Blanc April-July 1944 by completing M10A1 hulls as M36 vehicles with new guns and turrets. 413 produced by American Loco Co by converting existing M10A1, October-December 1944. 500 produced by Massey-Harris by converting existing M10A1, June-December 1944, 85 built by Montreal Loco Works, May-June 1945.
M36B1: An expedient design to meet increased demand for 90mm gun tank destroyers, this was produced by utilising the standard hull of the M4A3 medium tank fitted with the open-topped M36 type turret. 187 produced by Grand Blanc Arsenal, October-December 1944.
M36B2 utilised M10 hull and had detail changes including (usually) an armoured canopy over the open-topped turret.
M36B2: Further expedient type utilising the M10 instead of the M10A1 hull. Several detail improvements including armoured covers for turret on some vehicles. 237 produced by converting existing MIO by American Loco, April-May 1945.
76mm Gun Motor Carriage T72: This was an interim design to overcome the shortcomings of the M10 which suffered from an unbalanced turret. The T72 was a M10A1 with a redesigned turret based on the T23 medium tank turret but with the top removed and thinner walls. There was a large rear “box” for a counterweight and the 76mm gun M1 was replaced by the 3in. However, it was decided to replace the M10 with the M18 Hellcat and the M36 so the T72 project was dropped.
Designation: 90mm Gun Motor Carriage M36, M36B1, or M36B2
Crew: 5 (commander, driver, gun crew (3))
Battle weight: 62,000lb
Dimensions: Length 20ft 2in. Height 8ft 11 in Width 10ft
Armament: Main: 1 x 90mm gun M3 Secondary: 1 x ·50 cal Browning MG (AA)
Armour thickness: Maximum 50mm Minimum 12mm
Traverse: 360° Elevation limits: +20° to -100
Engine: Twin GM 6- 71 diesels (M36B2), Ford GAA V8 petrol(M36, M36B1)
Maximum speed: 30mph
Maximum cross-country speed: 18mph (approx)
Suspension type: Vertical volute
Road radius: 150 miles
Fording depth: 3ft Vertical obstacle: 2ft
Trench crossing: 7ft 6in
Ammunition stowage: 47 rounds 90mm, 1000 rounds ·50 cal MG
Special features/remarks: Overcame turret and gunpower deficiencies of the M10 series and proved a potent and impressive type in service. Many M36 vehicles were conversions from M10 series. Principal American tank destroyer type in final year of the war. Distinguished from M10 series by turret shape and long gun, occasionally seen with muzzle-brake removed.