1985 OLDSMOBILE CUTLASS SUPREME

Typical onset: 80,000-140,000 mi

Symptoms: Slipping on 2-3 upshift or delayed engagement, No overdrive (4th gear) or harsh downshifts, Burned fluid smell, metal shavings in pan

Fix: THM200-4R (behind 231 V6 and 260 V8) is notoriously weak—input drum cracks, 3-4 clutch pack burns out. Rebuild requires 8-12 hours, but most shops recommend swapping to built unit or THM350 conversion. THM700R4 (305/307 V8) holds up better but still needs TV cable adjustment and regular fluid changes.

Estimated cost: $1,800-3,200

Typical onset: 100,000-150,000 mi

Symptoms: Engine rattling on cold start for 3-5 seconds, Check engine light with timing codes (if equipped), Hard starting when hot, rough idle, loss of power

Fix: Olds and Chevy small-blocks eat timing chains due to nylon cam gear teeth stripping and chain stretching. Requires front cover removal, 4-6 hours labor. Replace with double-roller chain kit, cam gear, crank gear, and always do the oil pump while you're in there. Buick 231 V6 has similar issue—nylon gear sheds teeth into oil pan.

Estimated cost: $650-1,100

Symptoms: Rough idle, stalling at stop signs when warm, Black smoke on acceleration, flooding when hot, Hesitation off idle, high idle speed won't drop

Fix: Q-jet carbs are workhorses but 40-year-old units have worn throttle shafts, hardened accelerator pump, clogged idle tubes. Proper rebuild takes 3-4 hours and requires someone who knows these—parts are $150-250. Ethanol fuel accelerates deterioration. Many owners swap to Edelbrock 1406 instead.

Estimated cost: $400-700

Symptoms: Body sag at doors, misaligned panels, Visible rust holes in rocker panels or quarter panels, Clunking over bumps from loose body mounts

Fix: G-bodies rust at body mounts, rear frame rails near leaf spring mounts, and floorpans under feet. Body mount replacement is 6-8 hours if frame is solid. Frame rust is terminal—not worth fixing. Always inspect carefully before purchase, especially salt-belt cars.

Estimated cost: $800-1,500

Typical onset: 90,000+ mi

Symptoms: Oil puddle under bellhousing area after sitting, Burning oil smell, drips on exhaust crossover, Low oil between changes, no visible leak up top

Fix: Rope-style rear main seals harden and leak with age. Proper fix requires transmission removal, 6-8 hours labor. Oil pan gaskets leak at corners. Many owners just keep topping off oil unless it's dripping constantly. Use high-mileage oil with seal conditioners to slow it down.

Estimated cost: $700-1,200

Symptoms: No-start condition, cranks but won't fire, Stalling when hot, restarts after cooling 20 minutes, Intermittent cutting out at highway speed

Fix: GM HEI distributors are reliable but pickup coil and ignition module fail with heat. Module clips to distributor under cap—$40 part, 20 minutes roadside fix if you carry a spare. Complete distributor overhaul with cap, rotor, coil, module runs 1.5 hours. Common failure item, smart to keep module in glovebox.

Estimated cost: $150-350

Symptoms: No heat or stuck on full heat, Coolant smell in cabin, wet passenger carpet, Windshield fogs constantly, sticky film inside

Fix: Heater core leaks are common in 40-year-old cars. Dash removal is 8-10 hours—brutal job. Blend door actuators stick or break, leaving you with no temperature control. Many owners bypass heater core if it leaks and don't need heat (southern cars). Core is $80, labor is the killer.

Estimated cost: $600-1,400