1972 GMC K2500

Typical onset: 80,000-150,000 mi

Symptoms: Rattling noise on cold start that quiets after warm-up, Loss of power and rough idle, Check timing and find it's retarded 8-15 degrees despite setting distributor correctly, Metal shavings in oil pan during changes

Fix: Replace timing chain, gears, and tensioner. On 307/350/402 engines this requires front cover removal, new gaskets, and often a new harmonic balancer and water pump while you're in there. Budget 6-8 hours labor for a thorough job with clean-up.

Estimated cost: $800-1,400

Typical onset: 100,000-180,000 mi

Symptoms: Gear oil leak at rear of transfer case onto crossmember, Grinding or howling noise from transfer case in 2WD or 4WD, Play in rear output shaft (grab driveshaft and check for vertical movement)

Fix: Common failure point due to worn rear output bearing letting the shaft wobble and chew up the seal. Requires t-case removal or at minimum rear yoke removal, bearing race extraction, and seal replacement. If bearing race spun in housing, the case is junk. 4-6 hours labor depending on access and rust.

Estimated cost: $500-900

Symptoms: Flooding and raw fuel smell after sitting, Hesitation on acceleration or stumbling when cold, Black smoke and poor fuel economy (8-10 mpg instead of 11-13), Hard starting when hot

Fix: The Rochester Quadrajets on these trucks need rebuilds or replacement after decades of ethanol fuel deteriorating seals, needle seats, and accelerator pump components. A proper rebuild kit and careful work takes 3-4 hours. Many shops just swap on a remanufactured unit (1.5 hours) or convert to Edelbrock which eliminates future issues.

Estimated cost: $350-750

Typical onset: 60,000-120,000 mi

Symptoms: Clunking when engaging 4WD or during tight turns in 4WD, Vibration that worsens with speed in 4WD mode, Wheel bearing growl that changes with steering input, Grease leaking from inner or outer axle shaft boots

Fix: The Dana 44 front axle uses CV-style Rzeppa joints at the wheels and standard u-joints at the differential. The u-joints wear and require pressing out—2 hours per side. Wheel bearings require hub disassembly and bearing race removal, 3-4 hours per side. Often find both bad on same side due to neglected maintenance.

Estimated cost: $400-800 per side

Symptoms: Fuel gauge reads empty, full, or bounces erratically regardless of fuel level, Hard starting after sitting overnight (mechanical pump trucks), Fuel starvation and stalling on inclines with less than 1/4 tank

Fix: These trucks use a mechanical pump on the engine, but the in-tank sending unit float and rheostat corrode after 50 years. Requires dropping the tank (rusty straps are a nightmare—budget extra time), replacing sending unit. If tank is rusty inside, replacement or sealing necessary. 3-5 hours depending on rust and whether tank replacement is needed.

Estimated cost: $300-900

Symptoms: Soft or spongy brake pedal that goes to floor, Brake fluid leak visible on booster, firewall, or backing plates, Pulling to one side during braking, Parking brake ineffective

Fix: Single-reservoir master cylinders on '72s are dangerous when they fail. Wheel cylinders on rear drums seize or leak. Master cylinder replacement is 2 hours with bleeding. Rear wheel cylinders are $150-250 per axle in labor. If doing rear brakes, replace ALL rubber components—these are 50-year-old originals in many trucks.

Estimated cost: $400-800

Symptoms: Visible rust perforation on frame rails, especially behind cab and front of rear axle, Cab body mounts rotted through causing cab sag or movement, Clunking over bumps from cab shifting on frame, Steering box mount area rust causing loose steering

Fix: Not a repair job but a deal-breaker inspection point. Rust belt trucks often have terminal frame rot that makes them unsafe. Surface rust is fine, but holes or severe scaling in critical areas (steering box mount, spring hangers, crossmembers) mean walk away. Cab mounts can be replaced (8-10 hours labor lifting cab) but underlying frame rust usually accompanies it.

Estimated cost: $800-2,000 for cab mounts only if frame is solid