Peterbilt 579 Specs Explained: Engines, Weights and Sleepers
Peterbilt 579 engines, transmissions, weight limits, sleepers and tanks from the maker's data, plus a checklist for buying a used 579 in the UAE.
By Sufian7 min read
The Peterbilt 579 is a North American on-highway tractor, and a steady number of them reach the UAE used. Most sellers describe them with a few words: "605 hp, 80-inch sleeper". The maker's data says more than that, and some of it changes what you should pay and what you should check.
Everything below is Peterbilt's or PACCAR's own figures. The 579 is built for North America, and Peterbilt does not publish a Gulf-specification variant, so treat any truck you see here as an import and confirm what is actually fitted to it.
What Peterbilt does not publish
Two gaps catch buyers out, so they come first.
- No model-level GVWR or GCWR. Peterbilt says the ratings follow the installed components and the label on the door jamb. The weight figures in this guide are component limits (engine, transmission, axle), not a rating for the whole truck.
- No wheelbase range, overall length or overall height for the complete truck. Wheelbases are built to customer order. Peterbilt does publish the cab and sleeper dimensions, which are covered below.
If a seller quotes a gross combination weight, ask to see the door label or the build sheet.
Engines
The 579 page names six engines. Power and torque are the maker's.
| Engine | Displacement | Power | Torque |
|---|---|---|---|
| PACCAR MX-11 | 10.8 L | 332 kW (445 hp) | 2,305 Nm (1,700 lb-ft) |
| PACCAR MX-13 | 12.9 L | 380 kW (510 hp) | 2,508 Nm (1,850 lb-ft) |
| Cummins X15 (top rating) | 15 L | 451 kW (605 hp) | 2,779 Nm (2,050 lb-ft) |
| Cummins X15N | 14.5 L | up to 373 kW (500 hp) | up to 2,508 Nm (1,850 lb-ft) |
| Cummins ISX12N | 11.9 L | up to 298 kW (400 hp) | up to 1,966 Nm (1,450 lb-ft) |
| Cummins L9N | 8.9 L | 239 kW (320 hp) | 1,356 Nm (1,000 lb-ft) |
The "605 hp, 2,050 lb-ft" in many adverts is the top rating across the whole engine range, including Cummins. It is not the PACCAR MX-13, which is 510 hp and 1,850 lb-ft. Peterbilt's page names only the PACCAR MX-13 and MX-11 in its text, so a seller claiming 605 hp should be able to show you a Cummins X15 on the engine plate.
The maker also gives dry weights for the PACCAR engines: 1,134 kg for the MX-13 and 998 kg for the MX-11.
Transmissions
| Transmission | Type | Limits (maker's) |
|---|---|---|
| PACCAR TX-12 | 12-speed automated, 2 reverse | Engines to 510 hp / 1,850 lb-ft; GCWR to 110,000 lb (49,895 kg) |
| PACCAR TX-12 PRO | 12-speed automated, extreme-duty clutch | Engines to 455 hp / 1,700 lb-ft; GCWR to 70,000 lb (31,751 kg) |
| PACCAR TX-18 | 18-speed automated, vocational and heavy haul | Engines to 510 hp / 1,850 lb-ft; operating weight to 140,000 lb (63,503 kg) |
| Endurant HD | 12-speed automated | On-highway efficiency |
| Endurant XD | 18-speed automated | Vocational and heavy haul |
| Eaton Fuller FR/RT | Manual | 9, 10, 11, 13, 15 or 18 speeds |
| Eaton UltraShift PLUS | Automated | 10, 11, 13 or 18 speeds |
The point for a UAE buyer is the match between engine and gearbox. A TX-12 PRO behind a 1,850 lb-ft engine is outside the PACCAR Powertrain page's 1,700 lb-ft limit. Peterbilt's own 579 page gives a different, lower torque limit for the same gearbox (1,000 lb-ft), so the two pages disagree. Whichever is right, ask for the build sheet and check what is actually fitted. For heavy-haul or low-loader work, look for the 18-speed TX-18 or a manual.
Axles and weight limits
| Item | Maker's figure |
|---|---|
| Front axle capacity | 6,622 kg (14,600 lb); minimum option 5,443 kg (12,000 lb) |
| Rear axle capacity | 20,865 kg (46,000 lb); minimum option 9,525 kg (21,000 lb) |
| PACCAR DX-40 tandem rating | 18,144 kg (40,000 lb) |
| DX-40 axle GCW limit | 36,287 kg (80,000 lb) |
| MX-13 engine, max operating weight | 63,503 kg (140,000 lb) |
| MX-11 engine, max operating weight | 49,895 kg (110,000 lb) |
The DX-40 drive axle comes with ratios from 2.47 to 3.70, rated at 1,650 lb-ft in straight torque and 1,850 lb-ft in multi-torque. A low ratio suits highway running. A high ratio suits heavy hauling at lower speed. If the truck will pull a lowbed, the axle ratio matters as much as the engine.
Cab, sleepers and dimensions
The sheet we hold is for the 579 with a 124 in bumper-to-back-of-cab and a set-back front axle: 3.15 m. The 118 in version is 2.997 m. Overall width is 2.388 m, or 3.063 m over the mirrors. The cab roof stands 2.052 m above the bottom of the frame rail.
Sleeper options run from 44 in to 80 in.
| Sleeper | Length | Roof height above frame |
|---|---|---|
| 44 in (low roof) | 0.914 m | 2.126 m |
| 58 in (low roof) | 1.219 m | 2.172 m |
| 58 in (high roof) | 1.219 m | 2.586 m |
| 72 in (high roof) | 1.600 m | 2.586 m |
| 80 in (high roof) | 1.753 m | 2.637 m |
The 80 in UltraLoft gives 2.438 m of headroom and 1.982 m³ of storage. If your drivers rarely sleep in the truck, a day cab or a small sleeper may be all you need, and a smaller sleeper gives a lower roof. Check the sleeper-to-cab opening if your drivers are tall: the maker gives 1.245 m high by 1.73 m wide for a low roof and 1.689 m by 1.73 m for a high roof.
Fuel and DEF tanks
- Fuel: from 151 L (40 US gal) up to 568 L (150 US gal). Tank diameters are 20, 23 or 26 in.
- DEF: 38.6 L (small), 60.9 L (medium), 76.1 L (large). The aerodynamic mediums and larges are 52.6 L and 67.8 L.
Ask how many tanks are fitted and of what size. A truck with the 151 L option has far less range than one with the 568 L tank, and that changes how you plan a day.
The 579 against the 389 and the Kenworth T680
| Peterbilt 579 (124 in BBC) | Peterbilt 389 (131 in BBC) | Kenworth T680 | |
|---|---|---|---|
| Bumper to back of cab | 3.15 m | 3.343 m | 3.165 m (day cab) |
| Cab roof above frame | 2.052 m | 2.017 m | 2.129 m (day cab) |
| Overall width | 2.388 m | 2.408 m | Cab 2.474 m (front view) |
| Width over mirrors | 3.063 m | not published | 3.04 m |
| Engines | MX-11, MX-13, Cummins | Not published | MX-11, MX-13 |
The Peterbilt 389 went out of production in May 2023, and Peterbilt publishes no engine or weight figures for it, so our page is dimensions only.
The Kenworth T680 is the 579's direct competitor. It also uses the PACCAR MX-13 (405 to 510 hp, 1,550 to 1,850 lb-ft) and MX-11 (355 to 445 hp, 1,250 to 1,700 lb-ft), and the PACCAR DX-40 tandem axle with the MX-13. Kenworth publishes no GVW, GCW, fuel tank or weight figures in the sources we hold, either. The engines and the drive axle are shared across the two trucks.
What to check on a used 579
- Engine plate and build sheet. Confirm the engine against the list above, and the gearbox against its limits.
- Door-jamb label. The ratings follow the installed components, so the label is the only reliable source of the truck's weight rating.
- Service intervals. The maker's schedule lists engine oil and filter at 120,000 km and the fifth wheel at 24,000 km, or monthly. First-fill axle and gearbox oil is changed once at 4,800 to 8,000 km, then checked every 24,000 km. Ask for the records against those.
- Fifth wheel. Look for wear on the jaws and plate, and check it has been greased.
- DEF system. The truck carries a DEF tank, so ask whether the emissions system is intact and working, and what the seller knows about the fluid it has run on.
- Cooling and air conditioning. The 579 is built for North American climates. Ask how the truck has been prepared for the summer here, and check the radiator and the cab air conditioning.
- Sleeper and cab. Check the seals and the mattress for water damage, and the door between cab and sleeper.
- Import paperwork. Check the registration and the import documents match the VIN.
Browse trucks for sale on EquipmentsFinder, or open the full Peterbilt 579 page for the maker's data with sources.
