1978 PONTIAC VENTURA

Typical onset: 80,000-120,000 mi

Symptoms: Pink or milky transmission fluid indicating coolant contamination, Transmission slipping or delayed engagement after cooler ruptures, Overheating transmission, burnt smell, Radiator showing oil in coolant overflow

Fix: The internal transmission cooler in the radiator fails and cross-contaminates coolant with ATF, destroying the transmission within days if driven. Requires radiator replacement (or upgrade to external cooler), complete transmission flush or rebuild if contamination occurred, and all new fluids. Preventive external cooler install: 2-3 hours. Full damage control with transmission rebuild: 12-16 hours total.

Estimated cost: $400-800 preventive cooler upgrade, $1,800-3,200 if transmission rebuild needed

Typical onset: 60,000-90,000 mi

Symptoms: Slipping between 1st and 2nd gear under load, No 3rd gear or falls out of 3rd on highway, Delayed engagement into reverse, Metal shavings on dipstick

Fix: The TH200 (metric transmission) behind the 231 V6 was notoriously weak—thin bands, marginal clutch packs, and poor tolerances. Fails early especially if used for towing or spirited driving. Rebuild with upgraded components: 8-12 hours. Many owners swap to TH350 from V8 model for reliability, adding 4-6 hours for adapter and driveshaft work.

Estimated cost: $1,400-2,200 rebuild, $1,800-2,800 TH350 swap

Symptoms: Chronic stalling at idle when warm, Hesitation on acceleration, flat spots, Hard starting when hot, Black smoke and terrible fuel economy (8-12 mpg)

Fix: The Dualjet or Varajet carburetors paired with early emission controls create driveability chaos. Vacuum leaks, stuck choke, failed idle air bleeds, and lean mixture screws tampered with over decades. A proper rebuild with correct jetting and vacuum system restoration: 4-6 hours by someone who knows these carbs. Band-aid fixes waste time and money. Many convert to Edelbrock or Holley: 6-8 hours including tuning.

Estimated cost: $450-750 proper rebuild and tune, $800-1,200 aftermarket carb swap

Typical onset: 100,000-150,000 mi

Symptoms: Heavy knocking on cold start that quiets slightly when warm, Low oil pressure at idle (under 10 psi), Metallic rattle under acceleration, Oil consumption over 1 quart per 500 miles

Fix: The Pontiac and Chevy 350s in these cars wear main and rod bearings from infrequent oil changes and poor 1970s oil quality. Crank needs measuring and possible turn or replacement. Full bottom-end rebuild with crank R&R, new bearings, freeze plugs, and gaskets: 18-24 hours in-chassis, 14-18 hours if pulled. Many opt for reman long block swap instead: 16-20 hours.

Estimated cost: $2,500-4,000 in-chassis bottom-end rebuild, $3,200-4,800 long block swap

Typical onset: 70,000-110,000 mi

Symptoms: Clunk when shifting from park to drive or reverse, Vibration at idle in gear, Exhaust contact noise under acceleration, Visible sag of transmission tail housing

Fix: The rubber transmission mount deteriorates and collapses, letting the tailshaft drop and potentially contact the driveshaft or exhaust. Easy fix but requires supporting transmission. Replace mount and inspect crossmember for cracks: 1-1.5 hours.

Estimated cost: $120-220

Symptoms: Fuel smell under car, especially after sitting, Fuel stains on driveway near tank or along frame rail, Hard starting due to restricted flow from rusted filter, Engine stumble under load from fuel starvation

Fix: Steel fuel lines along the frame rail corrode from road salt and age, especially in the Midwest and Northeast. In-tank sock filter also rusts. Requires dropping tank, replacing lines from tank to pump and pump to carb, new filter, and checking tank interior for rust scale. Full fuel system refresh: 6-9 hours depending on line routing and tank condition.

Estimated cost: $500-900