1970 GMC K1500

Typical onset: 80,000-150,000 mi or unknown history

Symptoms: Rattling noise on cold start that quiets after warm-up, Rough idle or backfiring through carburetor, Hard starting or won't start after sitting, Check timing and find it's jumped 5-10 degrees

Fix: Replace timing chain, gears, and damper. Nylon cam gear teeth strip on original equipment. Requires front cover removal, 6-8 hours labor for experienced tech. Always replace oil pump and gaskets while you're in there.

Estimated cost: $800-1,400

Typical onset: Any mileage on original parts (50+ years old)

Symptoms: Clunking over bumps from front end, Excessive play in steering, wanders on highway, Front wheel wobble at low speeds, Grease leaking from knuckle seals

Fix: Dana 44 front axle uses kingpin-style knuckles instead of ball joints. Kingpin bushings wear oval, bearing races pit, and seals leak. Full rebuild per side: 8-10 hours for both sides including new bushings, bearings, seals, and kingpins. Requires press work and precision reaming.

Estimated cost: $1,200-2,200

Symptoms: Visible rust-through on frame rails behind cab or at rear crossmember, Cab visibly sagging or misaligned doors, Cracked or crumbling rubber cab mounts, Floor pan rust from inside-out

Fix: Northern trucks often have compromised frames at the rear spring hangers, crossmembers, or where cab mounts bolt through. Cab mount replacement requires lifting cab off frame (12-16 hours labor). Frame section replacement requires welding certification and significant fabrication. Many trucks are too far gone.

Estimated cost: $2,500-6,000+ depending on extent

Typical onset: 100,000+ mi or abused in 4WD

Symptoms: Gear oil leak at rear of transfer case, Growling or grinding noise in 4WD, Vibration under load in 4-wheel drive

Fix: The NP205 is nearly bulletproof, but the rear output bearing and seal wear from driveline angle issues or high mileage. Requires dropping rear driveshaft, removing output housing (3-4 hours). Often find worn splines on output shaft requiring full rebuild.

Estimated cost: $400-900

Symptoms: Black smoke on acceleration, Fuel smell, raw gas dripping from carb, Hesitation or bog off idle, High idle or won't idle down when warm

Fix: Original Q-Jets have worn throttle shafts causing vacuum leaks, hardened accelerator pump diaphragms, and clogged jets from ethanol fuel. Full rebuild kit and proper setup takes 4-5 hours for someone who knows these carbs. Many hacks just slap on a cheap Edelbrock instead.

Estimated cost: $350-700 for proper rebuild

Symptoms: Spongy brake pedal or pedal goes to floor, Brake fluid leaking at wheels or under dash, Pulling to one side during braking, Rear brakes locking up prematurely

Fix: Single-reservoir master cylinders are dangerous by modern standards, and all rubber components are 50+ years old. Wheel cylinders seep and contaminate shoes. Complete brake system overhaul: master, wheel cylinders, hoses, hardware, shoes, drums turned (6-8 hours). Many owners convert to dual-reservoir master for safety.

Estimated cost: $600-1,200

Typical onset: Variable, often age-related

Symptoms: Transmission leak at tailhousing, Late or harsh 2-3 shift, Transmission blowing ATF out dipstick tube, White smoke from exhaust (modulator failed)

Fix: Rear seal replacement requires driveshaft removal and tailhousing R&R (2-3 hours). Vacuum modulator diaphragm failures suck ATF into intake manifold. These transmissions are tough but often have 50 years of wear. If shifting poorly, plan for rebuild.

Estimated cost: $250-500 for seal/modulator, $1,800-2,800 for rebuild