1981 CHEVROLET BLAZER

Typical onset: 80,000-140,000 mi

Symptoms: Slipping between 1st and 2nd gear under load, Delayed engagement when shifting into drive or reverse, Burnt transmission fluid smell and dark red or brown fluid, Loss of forward gears but reverse still works (sprag failure on TH350)

Fix: Full transmission rebuild required including bands, clutches, seals, and torque converter. Expect 12-16 labor hours for R&R and rebuild. TH350 sprag clutch failures are notorious. Replace transmission cooler lines and external filter while it's out.

Estimated cost: $1,800-3,200

Typical onset: 120,000-180,000 mi

Symptoms: Heavy knocking from bottom end that worsens with RPM, Metal shavings in oil or sparkles on dipstick, Sudden loss of oil pressure, Spun bearing visible on oil analysis

Fix: Requires full bottom-end rebuild or short block replacement. Main bearings and rod bearings wear from age, poor oil change intervals, and running hot. Plan on 20-28 hours for complete teardown, machine work, and reassembly. Heads should be pulled and checked for cracks while you're in there.

Estimated cost: $3,500-6,000

Symptoms: Hard starting when cold or after sitting overnight, Stumbling and hesitation on acceleration, Black smoke from exhaust and fuel smell, Flooding or leaking fuel from carb base, Engine dies at idle or won't hold idle speed

Fix: Rochester Quadrajet or Holley carburetors gum up from ethanol fuel and sitting. Complete carb rebuild with kit runs 3-5 hours. Replace rubber fuel lines from tank to pump and pump to carb—they rot from inside out. Fuel filter typically clogged solid. Add fuel tank cleaning if rust present.

Estimated cost: $600-1,200

Typical onset: 60,000-100,000 mi

Symptoms: Clunking when turning in 4WD, Vibration during acceleration in 4WD, Clicking or popping from front differential area, Grease leaking from CV boots on axle shafts

Fix: Front axle shafts use enclosed CV joints that fail from torn boots and water intrusion. U-joints on driveshafts wear out from lack of greasing. Front axle CV joint replacement requires 4-6 hours per side with hub removal. Driveshaft U-joints are 2-3 hours total.

Estimated cost: $800-1,400

Typical onset: 70,000-120,000 mi

Symptoms: Brake pedal sinks slowly to floor when holding steady pressure, Hard brake pedal requiring excessive force, Hissing sound from under dash when pressing brakes, Brake fluid disappearing with no visible external leaks

Fix: Single-reservoir master cylinders leak internally, and vacuum boosters rupture diaphragms. Master cylinder replacement is 2-3 hours including bench bleeding and line work. Booster adds another 2-3 hours. These trucks use dual-diaphragm boosters that fail more often than later models.

Estimated cost: $400-900

Symptoms: Visible rust-through on frame rails behind cab, Body separated from frame or sagging at mounts, Creaking and popping noises over bumps, Doors won't close properly or alignment changes

Fix: Northern trucks rust badly at body mounts, rear frame rails, and rocker panels. Body mounts rot out completely. Replacement requires lifting body off frame—expect 8-12 hours minimum for all mounts. Frame section repairs require welding and fabrication, adding significantly to cost depending on severity.

Estimated cost: $1,200-3,000

Typical onset: 100,000-150,000 mi

Symptoms: Grinding when shifting into or out of 4WD, Pops out of 4-Low under load, Metal shavings in transfer case fluid, Whining or rattling noise from center of vehicle in 4WD

Fix: NP208 chain-drive transfer cases wear shift forks and stretch chains. Requires case removal and rebuild with new chain, bearings, and fork pads. Labor runs 8-10 hours for removal, rebuild, and reinstall. Aluminum case half can crack requiring replacement case.

Estimated cost: $1,200-2,200