Frequently Asked Questions About Peterbilt 359 Transmission Coolers
What size transmission cooler do I need for my Peterbilt 359, and how do I determine if I need an upgrade?
The stock transmission cooler size varies by year and engine configuration, but most Peterbilt 359 models came with either a 20,000 or 30,000 GVW rated cooler. To determine if you need an upgrade, check your transmission temperature gauge - if it regularly exceeds 200°F during normal operation or 220°F when pulling heavy loads, you should upgrade. For trucks with CAT 3406 or Cummins Big Cam engines pulling 80,000+ lbs, we recommend a minimum 40,000 GVW rated cooler. Always match or exceed your transmission manufacturer's BTU requirements.
Will these transmission coolers fit my 1967-1987 Peterbilt 359, and what modifications are required for installation?
Our transmission coolers are designed to fit all Peterbilt 359 models from 1967-1987, though mounting brackets may vary by year. Pre-1973 models often require adapter brackets (sold separately) due to different frame rail spacing. Most installations require no cutting or welding - coolers mount using existing frame holes or universal brackets. You'll need approximately 3-4 hours for installation, basic hand tools, and new transmission cooler lines. Extended hood models may require longer hoses than standard configurations.
What's the difference between tube-and-fin versus plate-and-fin coolers, and which performs better?
Plate-and-fin coolers offer 25-40% better cooling efficiency than tube-and-fin designs and are more resistant to road debris damage. Tube-and-fin coolers are typically less expensive and easier to repair if damaged. For heavy-haul applications or hot climate operation, we strongly recommend plate-and-fin coolers. Most modern retrofits use aluminum plate-and-fin construction, which provides excellent heat dissipation while weighing 40% less than older brass/copper units.
Can I mount the transmission cooler in front of my radiator, or should I use a remote mount location?
Front-mount installations (in front of the radiator) provide the best cooling efficiency as they receive direct airflow. However, this location exposes the cooler to more road debris. Remote mounting options include behind the cab or along the frame rails with electric fans. Front mounting is recommended for most applications unless you frequently operate in areas with heavy debris or need to preserve front-end appearance. Ensure at least 1 inch of clearance between the cooler and radiator to prevent airflow restriction.
What fittings and hoses do I need, and are they included with the cooler?
Most transmission coolers include basic mounting hardware but not hoses or fittings. You'll need high-pressure transmission cooler hose (typically 3/8" or 1/2" ID) rated for at least 300 PSI and 300°F. Fitting requirements vary by transmission type: most use either 1/4" NPT or 5/16" inverted flare connections. Allison automatics typically require -6 AN fittings. Budget for an additional $75-150 for quality hoses and fittings. We recommend using brass fittings over aluminum to prevent galvanic corrosion.
