Description

Peterbilt 320 Technical Manual – Factory Body Builder Specs for San Antonio Shops

If you’ve ever had a body shop hand you a frame modification spec that doesn’t match the actual rail thickness, you know the headache. Aftermarket manuals love to generalize. This Peterbilt 320 Technical Manual doesn’t. It’s 76 pages of factory-level data from Peterbilt Motors Company, covering every suspension layout from the Reyco 79K Single to the Hendrickson RS, and telling you exactly where the torque specs live (page 5-4). I’ve torqued more head bolts than most of you have had hot meals, and I still reach for a factory document when the frame drilling calls for that spec.

Torque Specs You Can Trust

Page 5-4 in this manual gives you the torque requirements for frame modifications. That’s not a generic number pulled from a third-party database. It’s the same spec Peterbilt uses on the assembly line. Miss that and you’ll have loose crossmembers or stripped holes. The manual also walks you through drilling rails on page 5-1, so you know exactly how to avoid cracking the rail web. No guesswork, just a table you can read while you’re under the truck.

Suspension Layouts: 14 Configurations Documented

Section 3 is a goldmine if you’re hanging a body on a 320. It covers 14 rear suspension layouts: Reyco 79K Single, 102AR Single, Neway AD252, AD378, Peterbilt Air Leaf, Air Trac Single/Tandem/Tri-Drive, Low Air Leaf, Chalmers 854, Hendrickson HMX, RT/RTE, HN, R, and RS. Each layout shows you the frame height chart and clearance requirements. For a pusher or tag axle, you’ve got Hendrickson and Watson-Chalin layouts. The Ground Clearance Calculations (page 3-38) and Exhaust Height Calculations (page 3-37) are the kind of data that keeps your body from dragging on the first curb.

What Multiplexed Instruments Mean for Your Wiring

The electrical section (Section 6) dives into the Cab Electronic Control Unit (CECU) and how multiplexed instruments work. If you’ve ever chased a short in a body builder harness extension, the diagrams on page 6-5 and 6-6 show you exactly where the chassis harness and the body builder harness meet. The J1939 data link (page 6-7) is critical for integrating aftermarket controllers. For wiring diagram specifics, check the Peterbilt 320 Wiring Diagram.

Frame Modifications: When You Need to Drill or Cut

Section 5 covers drilling rails, modifying frame length, changing wheelbase, and crossmember placement. The torque requirement table on page 5-4 isn’t just a list of numbers; it includes fastener sizes and tightening sequences. If you’re adding a rear body mount using U-bolts (page 4-7), you need those specs to avoid warping the frame. Pair this with the Peterbilt 320 Operators Manual: Factory Specs & Procedures for day-to-day operation details.

PTO Installations: Transmission and Engine Mounted

Section 8 (labeled 7 in the PDF) gives you the full PTO picture. Transmission-mounted PTO (page 7-1), front engine PTO (page 7-3), and rear engine PTO (page 7-4) are all covered. The remote PTO control via the 12-pin connector (page 7-6) is especially useful for refuse trucks. If you’re dealing with a Manual Transmission PTO scenario, the instructions include the clutch and driveline clearances. The Peterbilt 320 User Manual – 211 Pages of OEM Factory Specs can supplement this with additional electrical troubleshooting.

One thing that separates this manual from cheap aftermarket reprints is the safety section. Section 2 goes through Federal Motor Vehicle Safety Standards (FMVSS) and Canadian Motor Vehicle Safety Standards (CMVSS) compliance. The safety signals on page 2-1 are no joke: skip these warnings and you can cause a frame failure or electrical fire. The Manual Transmission section also has a caution about PTO interlock switches. I’ve seen shops wire around them – don’t be that guy.

Does this manual cover my 2015 Peterbilt 320?

Yes – it covers trucks produced after November 2013.

What kind of suspension layouts are included?

Fourteen rear layouts including Reyco, Neway, Peterbilt Air Leaf, Air Trac, Chalmers, Hendrickson HMX/RT/HN/R/RS, plus pusher and tag layouts from Hendrickson and Watson-Chalin. Each layout has frame height charts, clearance numbers, and critical mounting dimensions. If you’re installing a body on a 320, you’ll find the exact suspension geometry you need without calling the dealer.

Bottom line: if you’re a shop that mounts bodies, modifies frames, or wires PTO controls on the 320, this manual saves you from rework and callbacks. Access the Factory Manual and put it on your tablet or print the tables – just don’t rely on a pirated copy. Your torque wrench deserves factory numbers.