Frequently Asked Questions About Kenworth T660 Transmission Coolers

Will these transmission coolers fit my specific year Kenworth T660?

Most aftermarket transmission coolers for the Kenworth T660 are designed to fit model years 2008-2016. However, there can be variations based on your specific engine configuration and transmission type. We recommend checking your VIN or contacting us with your truck's year and transmission model (such as Eaton Fuller 10-speed, 13-speed, or 18-speed) to ensure proper fitment. Some coolers are universal fit while others are year-specific, particularly for 2008-2010 models versus 2011-2016 models.

What size transmission cooler do I need for heavy hauling or mountain driving?

For heavy-duty applications like hauling 80,000+ pounds or frequent mountain driving, we typically recommend coolers with at least 20,000-30,000 BTU/hr cooling capacity. Look for coolers with 11" x 11" or larger core dimensions. Stacked-plate aluminum coolers generally provide better cooling efficiency than tube-and-fin designs for extreme conditions. If you're running in hot climates or pulling heavy loads regularly, consider adding an auxiliary cooler in addition to your OEM unit rather than just replacing it.

How difficult is the installation, and what additional parts might I need?

Installation typically takes 2-4 hours for someone with basic mechanical skills. You'll need standard hand tools, potentially new transmission cooler lines (3/8" or 1/2" depending on your setup), and fresh transmission fluid. Some installations require relocating the DEF tank on 2011+ models. Common additional parts needed include mounting brackets, hose clamps, and fittings. Many drivers report needing to modify or fabricate mounting brackets for perfect fitment, especially when upgrading to a larger cooler than OEM spec.

What's the difference between OEM replacement and heavy-duty aftermarket coolers?

OEM replacement coolers match your truck's original specifications and typically feature tube-and-fin construction with standard aluminum cores. Heavy-duty aftermarket options often use stacked-plate designs with larger surface areas and can offer 20-40% better cooling capacity. Aftermarket coolers may also feature reinforced mounting tabs, thicker cores, and upgraded fittings. While OEM replacements work fine for standard applications, aftermarket heavy-duty coolers are recommended for trucks that idle extensively, pull heavy loads, or operate in extreme temperatures.

How do I know if my transmission cooler is failing and needs replacement?

Common signs include transmission fluid temperatures consistently running above 200-220?F during normal operation, visible leaks around cooler connections, transmission slipping or delayed shifting, and contaminated transmission fluid (milky appearance indicates coolant mixing). Physical damage like bent fins, corrosion, or impact damage also warrants replacement. Most T660 owners report cooler issues around 300,000-500,000 miles, though this varies greatly based on maintenance and operating conditions. Installing a transmission temperature gauge can help you monitor cooler performance and catch issues early.