SU-76M TECHNICAL DISCREPANCY REPORT
ISSUE: Artificial Speed Governor (30 km/h) vs. Mechanical Reality (45 km/h).
1. The Drivetrain Logic
The SU-76M uses the GAZ-203 power unit (Tandem GAZ-11 engines) and a ZiS-5 4-speed gearbox.
Engine Redline: 3,400 RPM.
4th Gear Ratio: 1.00 (Direct Drive).
Final Drive Ratio: 6.13:1 (Standard T-70/SU-76M sprocket).
2. The Math (Diesel Mechanic’s Proof)
In 4th gear, there is no mechanical reduction in the gearbox. Power flow is direct.
Output Shaft RPM: 3,400 (Engine) ÷ 1.00 (Gear) = 3,400 RPM.
Sprocket RPM: 3,400 ÷ 6.13 (Final Drive) = 554.6 RPM.
Ground Speed: Given the track circumference and 554.6 RPM, the vehicle must travel at ~44.8 km/h.
3. The “Invisible E-Brake”
To achieve the current in-game limit of 30 km/h, the engine would require a governor set to 2,200 RPM. This contradicts every Soviet technical manual for the GAZ-11/GAZ-203 series, which lists peak power at 3,400 RPM.
4. Historical Context
The 30 km/h figure often cited by moderators comes from Narkomat instructions for convoy marches and green crews to prevent the early SU-12 parallel engines from overheating. The SU-76M (Modernized) fixed these issues with the tandem shaft, and trial records at the NIBT Proving Grounds confirm a top speed of 44.4 km/h.