1970 CHEVROLET BLAZER

Symptoms: Clunking on acceleration or deceleration, Excessive drivetrain vibration, Visible sagging of transmission tail housing, Shifter feels loose or binds

Fix: Transmission mounts rot out from road salt and age; crossmember often rusts through requiring welding or replacement. Expect 2-3 hours labor to drop the transmission enough to swap mounts and assess crossmember condition. If crossmember needs replacement, add another 2-4 hours for fabrication or rust repair.

Estimated cost: $400-900

Typical onset: 70,000-120,000 mi

Symptoms: Burnt transmission fluid smell, Slipping under load, especially when hot, Leaking cooler lines at radiator or fittings, Transmission won't shift properly after highway driving

Fix: Factory cooler setup is marginal, especially with the 350 and trailer use. Steel cooler lines rust and crack at bends. Proper fix includes replacing lines (1.5 hours), adding external cooler (2 hours), and fluid flush. If internal damage occurred from overheating, you're looking at rebuild territory.

Estimated cost: $350-700 for preventive; $1,800-3,200 for rebuild

Typical onset: 120,000-180,000 mi

Symptoms: Blue smoke on startup or deceleration, Excessive oil consumption (quart per 500-800 miles), Loss of compression in one or more cylinders, Blow-by visible at oil filler cap

Fix: These engines were often run hard, and cylinder taper wear is common. Rings alone won't fix it if bores are tapered beyond 0.006 inches—needs bore and hone. In-frame ring job is 12-16 hours; full rebuild with machine work runs 25-35 hours. Many shops recommend pulling for proper rebuild given age and likelihood of bearing wear.

Estimated cost: $2,800-5,500

Symptoms: Hard starting when hot, Stalling at idle after highway run, Engine stumbles or dies in summer heat, Fuel leaking from pump weep hole

Fix: Mechanical pumps on these small-blocks run hot and the diaphragms fatigue. Vapor lock is aggravated by heat soak from engine and lack of return line. Pump replacement is 0.8-1.2 hours; adding insulator block and rerouting lines for cooler operation adds another hour. Many owners convert to electric pump in rear for reliability.

Estimated cost: $180-350 mechanical; $300-550 electric conversion

Typical onset: 100,000-150,000 mi

Symptoms: Heavy knocking at idle that worsens with RPM, Low oil pressure (under 10 psi hot idle), Metal shavings in oil or filter, Visible crank endplay or wobble

Fix: Low oil pressure from worn oil pumps or neglected maintenance leads to main bearing damage. If caught early, bearings can be replaced with crank polished in-chassis (18-24 hours). If crank is scored or out-of-round beyond 0.002 inches, it needs removal and machine work or replacement—full short block territory at 30-40 hours.

Estimated cost: $1,500-2,800 bearings only; $3,500-6,000 short block

Symptoms: Doors don't align or close properly, Visible rust-through on frame rails behind cab, Body sits crooked or sags, Cracking around body mount points

Fix: Northern trucks especially have severe rust on rear frame rails and outriggers where body mounts bolt through. Body mounts themselves rot out completely. Assessing requires lifting body off frame (6-8 hours). Patching frame sections runs 15-25 hours depending on severity; full frame-off often needed for proper repair on rusty examples.

Estimated cost: $2,000-8,000 depending on rust severity