1978 PONTIAC LEMANS

Typical onset: 80,000-120,000 mi

Symptoms: Slipping between 1-2 shift or delayed engagement into drive, Burnt transmission fluid smell and dark red or brown fluid, Hard or banging shifts especially when cold, Complete loss of forward gears leaving only reverse

Fix: TH200 (behind V6 and small V8s) has a weak intermediate band and sun shell that crack under normal use. TH350 is more robust but still fails from neglected fluid changes. Rebuild requires 8-12 labor hours including R&R, new clutches, bands, seals, and torque converter inspection. Many shops recommend TH350 swap if originally equipped with TH200.

Estimated cost: $1,800-2,800

Symptoms: Hard cold starting requiring repeated pumping of throttle, Stumble or bog on acceleration from stop, Black smoke from exhaust and fuel smell in garage, Stalling at idle especially when warm

Fix: Rochester 2-bbl (M2ME/M2MC) and Quadrajet carbs on these develop leaking accelerator pump diaphragms, stuck choke pulls, and warped float bowls. Ethanol fuel eats original rubber parts. Proper rebuild with modern ethanol-resistant kit takes 3-4 hours including adjustment on vehicle. Many owners go to Edelbrock or Holley swap for reliability.

Estimated cost: $350-650

Typical onset: 60,000-100,000 mi

Symptoms: Clunk when shifting from park to drive or reverse, Excessive vibration at idle especially with A/C on, Visible engine tilting forward when revved in park, Driveline shudder during hard acceleration

Fix: Rubber in OE-style mounts deteriorates and separates from metal brackets. Transmission mount failure lets tailshaft drop and stresses driveshaft U-joints. Engine mounts are 2 hours labor, transmission mount is 1.5 hours. Replace all three at once since they age together.

Estimated cost: $400-650

Typical onset: 90,000-150,000 mi

Symptoms: Puddle of oil under bellhousing area after overnight parking, Oil dripping from rear of oil pan onto crossmember, Low oil level requiring frequent top-offs between changes, Blue smoke on startup if leak is severe

Fix: Two-piece rear main seal design is prone to leaking as rope seal hardens. Proper fix requires transmission removal—8-10 hours labor for seal, resurface flywheel if grooved, and replace oil pan gasket while accessible since it leaks from age and overtightened bolts crushing cork. Some shops use rear main seal additive as temporary fix but it rarely holds long-term.

Estimated cost: $800-1,400

Typical onset: 130,000-180,000 mi

Symptoms: Knocking sound from bottom end that increases with RPM, Low oil pressure at idle especially when hot, Metal shavings or glitter visible in oil filter during change, Sudden loss of oil pressure and seized engine if catastrophic

Fix: Neglected oil changes or sustained low oil level wipe bearings and score journals. Proper fix is engine removal and machine work—crank must be turned undersize or replaced, mains and rods replaced, and block align-honed. Full rebuild with R&R is 18-25 hours. Many owners opt for reman long block instead since machine work often exceeds cost of replacement.

Estimated cost: $3,500-5,500

Symptoms: Engine cranks but won't start or dies after running briefly, Loss of power or stalling in hot weather or after idling, Visible fuel leak at mechanical pump on side of block, Engine must cool 20-30 minutes before restarting

Fix: Mechanical fuel pumps driven by eccentric on camshaft develop torn diaphragms or weak springs. Vapor lock is common in hot weather because fuel lines run near exhaust manifolds and boil fuel. Pump replacement is 1.5 hours, lines require heat shielding or rerouting. Electric pump retrofit with return line costs more but solves vapor lock permanently.

Estimated cost: $250-600