Frequently Asked Questions About Kenworth W900B/W900L Drivetrain Parts
What's the difference between drivetrain parts for the W900B and W900L models?
While many drivetrain components are interchangeable between the W900B and W900L, there are key differences due to the wheelbase variations. The W900B (short hood) typically has a 119" BBC measurement, while the W900L (long hood) has a 130" BBC. This affects driveshaft lengths, carrier bearing placement, and some transmission mount configurations. Always verify your specific truck's wheelbase and year when ordering driveshafts, U-joints, or transmission components to ensure proper fitment.
Which transmission options are compatible with my W900B/W900L, and what adapters might I need?
Common compatible transmissions include the Eaton Fuller 13-speed, 18-speed, and 10-speed models, as well as automatic options like the Allison 4000 series. Most 1987-2010 W900B/W900L models use standard SAE bellhousing patterns, but you may need specific adapter plates when switching between manual and automatic transmissions. For engine-specific requirements, Caterpillar C15/3406 engines typically use SAE #1 housings, while Cummins ISX engines often require SAE #2. Always confirm your engine model and existing bellhousing before purchasing.
How do I determine the correct driveshaft length and U-joint size for my truck?
Measure from the transmission output yoke to the rear differential input yoke with the suspension at ride height. For tandem axle setups, you'll need measurements for both the main driveshaft and the inter-axle shaft. Standard U-joint sizes for W900B/W900L models include 1710, 1760, and 1810 series, with heavy-haul applications often requiring 1850 series. The correct size depends on your engine torque rating and gross vehicle weight. When in doubt, match the series number stamped on your existing U-joints or consult your truck's build sheet.
What are the most common clutch problems in W900B/W900L trucks, and which replacement kit should I choose?
Common issues include clutch chatter (often from worn pilot bearings or warped flywheels), premature wear from improper adjustment, and release bearing failure. For standard applications, 15.5" single-disc clutches work well, while heavy-haul or high-torque applications benefit from 15.5" dual-disc setups. Eaton Easy Pedal and Solo self-adjusting clutches are popular upgrades that reduce maintenance. Always replace the pilot bearing, release bearing, and inspect the flywheel surface when installing a new clutch. Most W900B/W900L models use pull-type clutches with 2" input shafts.
Can I upgrade my differential gears for better fuel economy or pulling power?
Yes, changing differential gear ratios is a common modification. For improved fuel economy on highway applications, consider switching from 3.70 or 4.11 ratios to 3.36 or 3.08. For better pulling power, ratios like 4.33 or 4.88 provide more torque multiplication. Keep in mind that gear changes affect speedometer accuracy and may require recalibration. Most W900B/W900L trucks use Eaton DS series or Meritor differentials. When changing ratios, replace both the ring and pinion as a matched set, and always use the manufacturer-specified gear oil weight and capacity.
