1995 GMC SIERRA 2500

Typical onset: 150,000-200,000 mi

Symptoms: Coolant in oil or oil in coolant without visible head gasket leak, Sudden loss of oil pressure, knocking from bottom end, White smoke on cold start that doesn't clear, Overheating despite new cooling system components

Fix: The 6.5L block casting is prone to cracking between cylinders and main webs, especially if overheated. Spun main or rod bearings are common due to marginal oiling. Full rebuild or replacement required—figure 30-40 hours for R&R and rebuild with machining. Many owners opt for 6.5L reman or swap to Duramax/Cummins.

Estimated cost: $6,000-10,000

Typical onset: 120,000-180,000 mi

Symptoms: Coolant loss with no visible leaks, steam from tailpipe, Misfires on one or more cylinders, Excessive oil consumption (quart every 500-1000 miles), Low compression on adjacent cylinders

Fix: Big block 454 runs hot and the OEM head gaskets fail, often taking out piston rings due to thermal stress. Head gasket job alone is 14-18 hours, but if rings are scored you're looking at full teardown. Short block replacement is 25-35 hours. Use better gaskets (Fel-Pro PermaTorque) and ARP studs.

Estimated cost: $3,500-8,500

Typical onset: 80,000-150,000 mi

Symptoms: Transmission fluid leaking at radiator connections, Pink or milky transmission fluid (coolant contamination), Transmission slipping or delayed engagement after coolant intrusion, Puddles under front of truck

Fix: The steel cooler lines rust through at the radiator fittings or develop stress cracks. If coolant gets into transmission, you need full flush or rebuild. Line replacement is 2-3 hours if caught early. If trans is contaminated, add 12-18 hours for rebuild. Many techs install external cooler and bypass radiator unit entirely.

Estimated cost: $300-600 for lines only, $2,000-3,500 if transmission damaged

Typical onset: 100,000-180,000 mi

Symptoms: Hard starting, extended cranking before firing, Loss of power, won't rev past 2000 RPM, Black smoke under load, Stalling at idle or when coming to stop

Fix: The Stanadyne DB2 injection pump on 6.5L diesels wears out from poor fuel quality and contamination. Pump failure often damages injectors too. R&R is 6-8 hours including fuel system bleeding and timing. Use quality fuel filters religiously and replace every 5,000 miles to extend pump life.

Estimated cost: $1,800-2,800

Typical onset: 60,000-100,000 mi

Symptoms: Clunking when shifting into gear, Vibration at highway speeds, Visible transmission sag when inspecting from side, Harsh engagement into reverse

Fix: The rubber transmission mount deteriorates from heat and weight, especially with the 4L80E and heavy loads. Creates driveline angle issues that accelerate u-joint wear. Replacement is straightforward—1.5-2 hours with proper jack support. Inspect crossmember for cracks while you're there.

Estimated cost: $200-350

Symptoms: Rough idle, surging, No-start condition after sitting, Water in fuel warning (if equipped), White or gray smoke

Fix: PMD/FSD (pump mounted driver) failures are infamous, but often triggered by fuel contamination. Water in fuel rots the fuel filter housing and injector lines. Full fuel system service includes filter, housing, water separator service, and often PMD relocation—4-6 hours. Relocating PMD to bumper with cooling module prevents repeat failures.

Estimated cost: $600-1,200

Typical onset: 100,000-150,000 mi

Symptoms: Power steering fluid leak at gearbox, Excessive play in steering wheel (more than 2 inches), Groaning when turning at low speed, Wandering at highway speeds

Fix: Heavy front end weight (especially with diesel and plow packages) wears out steering box seals and sector shaft. Rebuilds rarely last—replacement with new or quality reman is best. R&R is 3-4 hours including alignment check. Upgrade to later-model box if doing full front-end refresh.

Estimated cost: $500-900