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MOTRS

HK-HG Monaro / GTS

1968-1971 / Coupe / Australia

All HK-HG Monaro / GTS problems All workshop issues
Common Transmission

Muncie 4-Speed Synchro Wear

Symptoms

Grinding on gear changes, particularly second and third gear. Difficulty selecting gears under load.

Cause

The Muncie 4-speed's synchro rings wear over time, especially in cars that have been driven hard or used for motorsport. The M20 (wide ratio) and M21 (close ratio) are both affected.

Fix

Rebuild the gearbox with new synchro rings, bearings, and seals.

Budget $1,000-2,000 for a professional rebuild.

Muncie rebuild kits are available from American drivetrain suppliers.

The Muncie is a well-documented gearbox with excellent parts availability.

Cost mentioned in fix
Budget $1,000-2,000 for a

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Other known issues

Common Transmission

Turbo-Hydramatic (TH350) Automatic Wear

Slipping under load, delayed engagement from Park to Drive, harsh shifts, fluid leak.
Critical Engine, Chevrolet V8 (327ci / 350ci)

Intake Manifold Gasket Leaks

Coolant leak at the front or rear of the intake manifold. Coolant may drip externally or, worse, leak internally into the engine oil. May also cause a vacuum leak, resulting in rough idle and poor fuel economy.
Common Engine, Chevrolet V8 (327ci / 350ci)

Rochester Quadrajet Carburettor Issues

Hesitation on acceleration (bog), flooding, fuel smell, hard starting when hot, black smoke, erratic idle.
Critical Engine, Chevrolet V8 (327ci / 350ci)

Overheating Under Load

Temperature gauge climbs on highway drives, particularly towing or climbing hills. May push coolant out the overflow. Engine pings (detonation) under load.
Common Engine, Chevrolet V8 (327ci / 350ci)

Hydraulic Lifter Noise

Ticking or clattering from the top of the engine that varies with RPM. May be audible at idle and disappear at higher RPM, or vice versa.
Common Engine, Holden Six (186ci) and V8 (253ci)

Oil Leaks, Rear Main Seal

Oil drips from the bellhousing area. Oil accumulates on the underside of the engine and transmission.
View all 18 HK-HG Monaro / GTS problems