A snowmobile rear suspension assembly has a first and second suspension arms, a pair of slide rails pivotally connected to lower ends of the suspension arms and at least one shock absorber, a pair of extension arms pivotally connected to a rear portion of the pair of slide rails about a lateral axis and being pivotable between raised 5 and lowered positions about the lateral axis, a pair of rear idler wheels rotationally connected to a rear portion of the pair of extension arms, and at least one spring biasing the pair of extension arms toward the lowered position. At least a portion of at least one of the suspension arms is pivotable about a longitudinally extending axis relative to the pair of slide rails. A snowmobile having the rear suspension, a method 10 of replacing the slide rails of the rear suspension and a slide rails replacement kit are also disclosed.