SO-90 M36

_YugoSlav · October 1, 2024, 2:03am

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SO-90 M36

TL;DR: M36 Jackson with a 580 hp V-55 engine, NVD and Yugoslav M74 HEAT-FS shell.

History and Description

During the early 1950s, the American military provided the Yugoslav People’s Army (JNA) with a lot of armament assistance, focusing on defense against the Eastern Bloc’s main card - tanks. A good example of such armaments was the M36 tank destroyer. The first ten M36s were handed over to the JNA in 1953. Year after year, additional quantities arrived, and in 1957, when procurement through the MDAP was completed, the JNA possessed 399 TDs in two variants, M36 and M36B1. The vehicles that arrived in Yugoslavia featured steel roof armor and 90 mm M3A1 guns in place of the M3s. The M3A1 guns were capable of firing HEAT-FS rounds, but the JNA received none at the time. Both tank destroyers carried the same turret. The M36 differed from the M36B1 in that it used the M10A1 hull, with thin armor and decent mobility. Three-fourths of the 399 Jacksons in JNA were the M36 variant, representing a large percentage of the total.

Due to the lack of suitable successors, the M36 and M36B1 self-propelled guns survived numerous JNA reorganizations and changes, including the great wave of modernization during the 1970s and 1980s. The 90 mm gun was highly valued in the JNA for its anti-tank and fire support capabilities. The Soviet 100 mm T-12 towed guns were more powerful but inferior in mobility. As a means of extending the M36’s and M36B1’s service life, the Yugoslav military industry began complete modernization in the 1970s, which included: The replacement of the original petrol engine with the Soviet V-55 580 hp 12-cylinder diesel engine originally produced for the T-55A tanks. Due to the bigger engine, a square hole had to be cut out from the back panel of the vehicle and additional armored housing had to be welded around. An engine heater exhaust was added on the left side of the engine. To allow the integration of the cooling system the back lower panel of the vehicle had to be cut out and reworked. Due to the reduced space in the engine compartment, two cylindrical air filters were developed and placed on either side of the engine. Additionally, a new oil filter was developed. A completely new firefighting system was built in, with sensors located in all parts of the vehicle. The communication equipment was replaced with the Yugoslav radio device RUT-1 and internal vehicle communication was replaced with Yugoslav UMR. The entire vehicle’s electrical wiring was redone and upgraded. Driver’s infra-red lights were added and placed together with the main headlights inside an armored casing. Between 1955 and 1959, the M67 HE shell was developed. Then in 1974, the first series of M74 HEAT-FS was produced. The new projectile was a copy of the Soviet 100 mm BK-5M HEAT-FS shell. The tests showed that this projectile could penetrate the armor of most tanks at a distance of up to two kilometers. There were problems with projectile fins getting stuck on the muzzle brake so a big portion of vehicles had their bore evacuators and muzzle brakes removed.

During the Yugoslav wars, M36 and M36B1 self-propelled guns were firmly established as fire support weapons on all sides of the conflict. The good elevation of the gun made them useful in hilly and mountainous terrain since they could be used to shoot at targets located in elevated positions. To protect against projectiles with HEAT warheads, some vehicles were covered with thick rubber screens. M36 and M36B1 TDs were retired from all successor state armies after the war due to age, maintenance problems, and obsolescence. Many found their way to private collectors and museums all around the globe.

Specifications

Essentials
- Length; 5.97 m
- Width; 3.05 m
- Height; 2.61 m
- Mass; 27.7 t
- Crew; 5
Protection
- Armor;
  - hull: 19-38 mm,
  - turret: 31-76 mm
- APS; N/A
- ERA; N/A
- Smoke; possibly ESS
Mobility
- Engine; V-55, 580 hp
- Power/weight; 20.9 hp/t
- Top speed; 45 kph
- Amphibious; No
Firepower
- Main; 90 mm M3A1 gun
  - 47 rounds in total
  - Stabilizer; No
- Secondary; 12.7 mm M2HB machine gun
  - Penetration at 10 m; 31 mm
  - Fire rate; 577 shots/min
  - Belt capacity; 200 rounds

V series engine

A lot of conflicting information exists regarding which Soviet engine was used. It had to be either a V-2-34, V-54 or V-55. According to my research, it must have been a V-55 from a T-55A. V-54 engine has horizontal ridges on the lower part of the crankcase which are not present on the V-55. These ridges can’t be seen on two separate V-2-type engines installed in an M36, therefore they must be V-55 engines. Okay, so the engines were V-55s, but did they retain their original 580 horsepower, or were they downrated to 500 hp? This is now something I can’t figure out.

M36 engine #1. Note no horizontal ridges on the lower crankcase

M36 engine #2. Again, there are no horizontal ridges on the lower crankcase

V-2-34 engine looks nothing like the engines used in the M36s and is least likely the one used in the modernization

V-54 engine. Note the horizontal ridges on the lower part of the crankcase which aren’t present on the engines used in the M36s

V-54

V-55 engine with a very smooth lower part of the crankcase. In my opinion, the engine that was used in M36

V-55

Gallery

M36 Jacksons in JNA service before the modernization. The vehicles in the picture have 90 mm M3A1 guns with bore evacuators and muzzle brakes removed. In their place are thread-protecting rings.

M36 Jackson in JNA service before the modernization. The vehicle in the picture has a 90 mm M3A1 gun with a bore evacuator and a muzzle brake

M36 Jackson after the modernization. The key difference is the armored casing around the headlights

ex.Yugoslav M36 at Pivka Military Museum

1 Main headlight
2 Infra-red light
3 Blinker and blackout marker light
4 Blackout driving light

ex-Yugoslav M36 with missing lower back armor plate to allow the integration of the cooling system

ex-Yugoslav M36. The steel box under the removed lower back armor plate was added to accommodate part of the longer engine. Below the left exhaust, there is a circular cover for the heater’s exhaust.