HK-HG Monaro / GTS

1968-1971 / Coupe / Australia

All HK-HG Monaro / GTS problems All workshop issues

Common Transmission

Turbo-Hydramatic (TH350) Automatic Wear

Symptoms

Slipping under load, delayed engagement from Park to Drive, harsh shifts, fluid leak.

Cause

The TH350 is a reliable transmission but wears after decades of use. The clutch packs glaze and lose friction. The internal seals harden. The governor can stick, affecting shift timing.

Fix

Start with a fluid and filter service.

If problems persist, the transmission needs a rebuild ($1,500-2,500).

The TH350 is a well-understood unit with excellent parts availability and rebuild support.

Cost mentioned in fix

$1,500-2,500

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Other known issues

Common Transmission

Muncie 4-Speed Synchro Wear

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

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