Left Hand vs. Right Hand
It can get pretty confusing trying to determine which side of the truck is left hand, versus which side is right. It changes based on which way you’re looking at the truck! Luckily, in the world of air brake camshafts, it is standard across the board.
According to manufacturer specifications, when replacing a camshaft located on the driver side of the vehicle, you will want to look for a Left Hand Camshaft. To ensure you’ve got the correct camshaft, turn the S groove to face you. If the Left hand will fit in the groove, you’re holding a left hand camshaft.
If replacing a camshaft on the passenger side, you’ll replace it with a Right Hand Camshaft. To ensure you’ve got the correct camshaft for that side of your truck or trailer, turn the S groove toward you once again. A right hand camshaft should have the groove on the right hand side.
Other important factors when determining the correct S-Cam for your Truck or Trailer include counting the number of splines on the end of the shaft.
You'll also need to measure, measure, and you guessed it, measure.
One of the first things to measure is the bearing surface underneath the camshaft head. This is also known as the Spider Journal. Along with the Spider Journal, you'll want to measure the support bushing diameter. This is the area above the splines.