1971 BUICK GS

Typical onset: 80,000+ mi (often unknown actual mileage)

Symptoms: Delayed or harsh 1-2 shift, slipping under throttle, Transmission overheating, especially in stop-and-go or towing, Leaking cooler lines at crimped fittings or corroded steel lines, Burnt transmission fluid smell, dark or metallic fluid

Fix: TH400 rebuild with updated clutches, bands, and seals takes 8-12 hours. Cooler line replacement adds 2 hours. Most also need the transmission mount replaced simultaneously due to oil saturation and age. Expect to find the original cooler lines rusted through at the frame routing points.

Estimated cost: $2,200-3,800

Typical onset: 100,000+ mi or unknown history

Symptoms: Low oil pressure at idle (under 10 psi hot), gauge bouncing, Deep knocking from lower engine, worse when warm, Metal flakes or bronze material in oil filter during changes, Severe crankshaft runout causing harmonic balancer wobble

Fix: Requires engine removal, full teardown, crank grinding (or replacement if more than 0.030" undersize already), new rod and main bearings, and typically new oil pump. Short block replacement is 18-24 hours; full rebuild with piston rings and valve work is 28-35 hours. The 455 cranks can crack at the journals if run with low oil pressure.

Estimated cost: $4,500-8,500

Typical onset: 80,000-120,000 mi

Symptoms: Blue smoke on startup or deceleration, Excessive oil consumption (1 quart per 500-800 miles), Low compression readings (under 120 psi) with wet test improvement, Fouled spark plugs, especially on cylinders 3, 5, 7

Fix: Proper fix is engine removal, bore honing or machining if taper exceeds 0.006", new rings, and valve seals while it's apart. Figure 22-28 hours for a complete ring job with head work. Shortcuts like high-mileage oil or additives just mask the problem temporarily. These engines were not designed for modern extended oil change intervals.

Estimated cost: $3,200-5,500

Symptoms: Hard starting when hot, requires multiple cranking attempts, Stumbling or hesitation off idle, flat spots during acceleration, Fuel smell in garage, leaking accelerator pump or bowl gaskets, Rough idle with black smoke indicating overly rich mixture

Fix: The Rochester carburetors (2-barrel or 4-barrel depending on engine) gum up badly if the car sat or used modern ethanol fuel without stabilizer. Full rebuild with new gaskets, needle/seat, accelerator pump takes 3-5 hours including proper adjustment. Replace rubber fuel lines and filter simultaneously—original steel lines rust from inside out. Many have incorrect replacement carbs that run too rich.

Estimated cost: $450-950

Symptoms: Clunking over bumps from front suspension, Wandering steering, needs constant correction on highway, Uneven tire wear on inside or outside edges, Alignment won't hold settings, camber/caster drift after alignment

Fix: Original rubber bushings are 50+ years old and turn to powder. Upper control arm shafts seize in the frame mounts. Proper repair means pressing out old bushings, cleaning rust from bores, installing poly or rubber bushings. Count on 6-8 hours for both sides with alignment. Front lower control arm bushings often need the shaft burned out. Ball joints usually need replacement at same time.

Estimated cost: $800-1,400

Typical onset: 60,000+ mi

Symptoms: Oil drips from bell housing area onto crossmember, Large oil spot under car after overnight parking, Oil coating on transmission case and starter, Visible seepage at oil pan rail, especially rear corners

Fix: The 2-piece rear main seal commonly leaks on these engines. Proper fix requires transmission removal (8-10 hours with rear main seal replacement). Oil pan gasket is 4-5 hours by itself but cork gaskets leak again within a year—use composite gasket material. Many mechanics will try rope seal installation without pulling transmission; this rarely works properly and wastes money.

Estimated cost: $950-1,800