1979 Commercial Trucks For Sale

Final drive ratio is the first thing to check on 1979 trucks for sale. Many were geared for the 55 mph era with direct-drive transmissions and 4.11 to 4.44 rears. That pulls hard at low speed but runs out of road speed and fuel economy on today’s highways. Re-gearing or moving to an overdrive Roadranger can make a big difference, but budget for driveshaft length changes and speedometer calibration. Expect 11R22.5 or 11R24.5 rubber, steel or aluminum hubs, and S-cam drum brakes without ABS. Most units will have manual slack adjusters unless they’ve been retrofitted. Verify brake lining thickness, drum condition, air compressor output and cut-in pressures, and that spring brake chambers and gladhands are in good shape.

Powertrains from this period are mechanical and very serviceable. Common engines include Cummins NTC Big Cam 250 to 400 hp, Caterpillar 3406A in the 300 to 425 hp range, and Detroit Diesel 8V71 or 8V92 two-strokes. They start and run without electronics and accept field repairs, but they are louder, may smoke under load, and typically return 4 to 6 mpg depending on gearing and duty. Jacobs engine brakes are a valuable upgrade on mountain routes. Transmissions are mostly Fuller Roadranger 9, 10, or 13 speed constant-mesh boxes. Clutch condition, input shaft wear, and synchronizer status on auxiliary boxes should be verified with a loaded road test. Cooling systems, charge air plumbing on turbo engines, and mechanical injection timing are worth a close look.

Chassis and cab specs reflect the pre-1982 overall length rules, so cabovers are common alongside long-hood conventionals. You will see Kenworth K100 and Peterbilt 352 cabovers, plus Peterbilt 359, Kenworth W900A, Mack R Model, International Transtar 4300, and Ford Louisville conventionals. Frames may be single or double-frame on vocational builds. Hendrickson walking beam, Mack Camelback, and Reyco spring suspensions dominate for durability, with early air ride options offering better ride but more plumbing to maintain. Expect incandescent sealed-beam lighting, minimal cab insulation, and R-12 HVAC systems that may have been converted to R-134a. Interior trim, dash panels, and cab glass can be hard to source on some models, so factor availability into restoration plans. Inspect for frame rail cracks at suspension hangers, double-frame delamination, crossmember rust, steering box play, and cab mount wear.

Compliance and use case matter with 1979 semi trucks. Engines from this era qualify for the ELD exemption by engine model year pre-2000, but state or local emissions rules can restrict operation. California’s Truck and Bus Regulation, certain port drayage rules, and local opacity standards may limit where a vintage commercial truck can run. For agricultural, logging, oilfield support, show truck, and regional limited-mileage work they can be cost effective. They couple to modern trailers using the standard SAE J560 7-way plug and gladhands, but verify fifth wheel height, kingpin setting, and that the tractor’s service and emergency air lines are clean and dry. If you need to power a dump or lowboy, confirm the transmission PTO and wet kit specs match the trailer. Pre-1981 VIN formats vary by manufacturer, so double-check title records and serial plates before purchase.