The 1979 Buick Regal sits on GM's G-body platform with decent bones but watch for transmission issues, Olds 350 diesel nightmares if equipped, and typical late-70s GM rust. The TH200/TH350 automatics are the real weak point, especially behind V8s.
TH200/TH350 Automatic Transmission Failure
Common · high severityTypical onset: 80,000-120,000 mi
Symptoms: Slipping on 1-2 or 2-3 shifts, Delayed engagement into gear, Transmission fluid burnt smell or dark color, Whining noise in gear
Fix: TH200 was undersized for V8 duty and fails early with clutch pack/band wear. TH350 is tougher but still sees valve body issues and sun shell failures. Rebuild takes 8-12 hours including R&R. Upgraded clutches and shift kit recommended during rebuild.
Estimated cost: $1,800-3,200
Oldsmobile 350 Diesel Engine Self-Destruction
Common · high severityTypical onset: 60,000-90,000 mi
Symptoms: White smoke on startup, Hard starting when warm, Head gasket leaks, Cracked cylinder heads, Main bearing failure
Fix: GM's notorious 5.7L diesel used gasoline engine architecture with weak head bolts and inadequate cooling. Head gasket failures lead to coolant in oil and catastrophic bearing damage. Most need complete engine rebuild or replacement. 20-30 hours for rebuild, 12-16 for engine swap.
Estimated cost: $3,500-6,500
G-Body Frame Rust and Body Mount Deterioration
Common · medium severitySymptoms: Sagging body on one side, Doors misaligned or hard to close, Visible rust on frame rails behind front wheels, Trunk floor rust-through, Rear spring hangers rusted
Fix: Body mounts rot out from trapped moisture, causing alignment issues. Frame rust concentrates at rear spring pockets and front control arm mounts. Body mount replacement is 4-6 hours. Frame rust requires sectioning/welding, 15+ hours depending on extent.
Estimated cost: $600-1,200 for mounts, $2,000-4,000+ for frame repair
Buick 231 V6 (3.8L) Timing Chain Wear
Occasional · medium severityTypical onset: 100,000-150,000 mi
Symptoms: Rattling noise on cold start, Check engine light or rough idle, Loss of power, Won't start after sitting
Fix: Nylon cam gear teeth wear and timing chain stretches, causing erratic timing. Can jump time and bend valves if it goes completely. Front cover removal required, 6-8 hours with accessories. Replace chain, gears, and front seal while in there.
Estimated cost: $800-1,400
Carburetor Issues - Rochester Quadrajet
Common · low severitySymptoms: Black smoke under acceleration, Hesitation or stumble when accelerating, Hard starting when hot, Fuel leaking from throttle shaft area, High idle or won't idle down
Fix: The Q-jet is rebuildable but needs it every 50k-70k due to ethanol damage to rubber parts and power piston wear. Throttle shaft bushings wear causing vacuum leaks. Full rebuild takes 2-3 hours off-car. Most shops just swap for reman unit.
Estimated cost: $350-650
Rear Main Seal and Oil Pan Gasket Leaks
Occasional · low severityTypical onset: 80,000+ mi
Symptoms: Oil puddle under engine after sitting, Oil coating on bellhousing, Low oil level, Blue smoke on startup
Fix: Two-piece rear main seals were marginal from the factory and leak with age. Oil pan gaskets leak at corners. Rear main requires transmission removal, 8-10 hours. Oil pan is 4-5 hours due to frame crossmember interference and motor mount work.
Estimated cost: $650-1,100 rear main, $400-700 oil pan
Buy a gas V8 or V6 model with solid frame and plan for a transmission rebuild - avoid the diesel like the plague.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.