The job of the transmission is to change the speed ratio
between the engine and the wheels. The transmission uses a range of gears --
from low to high -- to make more effective use of the engine's torque as
driving conditions change. The gears can be engaged manually or
automatically. Today's side x side vehicles all use a type of automatic
transmission called a continuously variable transmission or CVT.
Unlike traditional automatic transmissions used in cars that
are much too heavy for a side x side vehicle, CVTs don't have any sort of
gears. The CVT operates on a pulley system
that allows an infinite variability between highest and lowest gears with no
discrete steps or shifts.
CVTs used in Rhinos, RZRs, Rangers and Prowlers have three
basic components:
- A rubber belt
- A variable-input "driving" pulley
- An output "driven" pulley
The variable-diameter pulleys are the key to a CVT. Each
pulley is made of two cones facing each other. A belt rides in the groove
between the two cones. When the two cones of the pulley are far apart, the
belt rides lower in the groove, and the radius of the belt loop going around
the pulley gets smaller. When the cones are close together, the belt rides
higher in the groove, and the radius of the belt loop going around the
pulley gets larger.
One of the two pulleys is connected to the crankshaft of the
engine. This pulley is typically called the drive pulley. The second pulley
is called the driven or output pulley because the first pulley is turning
it. The driven pulley transfers energy to the transfer case and onto the
differentials, through the axles and out to the wheels.
On a Yamaha Rhino, the clutch sheave is part of the drive
pulley (right side in above image). When clutch sheaves are machined, it
allows the cones on the drive pulley to collapse even further which forces
the belt even higher between the cones. This translates to a higher
gear.
In this image, the engine is at low rpm. The drive pulley cones are
far apart causing the belt to ride low (smaller radius).
In this image, the engine is at high rpm. The drive pulley cones are
far apart causing the belt to ride high (larger radius).
When one pulley increases its radius, the other decreases
its radius to keep the belt tight. As the two pulleys change relative to one
another, they create an infinite number of gear ratios.
Remove seat base and plastic in front of seat. Remove bolt
from inner/front seat base that goes around below shifter.
Remove cover
Cover removed - Sheave is on the right.
Remove sheave "guard"
Guard removed
Bolts inserted to loosen belt
Clutch sheave removed from Rhino.
Old clutch sheave removed. There are eight weights.
Old weights are removed from the teflon covers
New weights are pressed into old teflon covers
New weights are all in place
Weights are greased and installed in the new sheave
Sheave is assembled
Now it is time to remove and replace the secondary spring
(part of the Duner's Kit) from the secondary sheave. This is a special spring removal tool and wrench
from Yamaha. Changing the secondary spring is very difficult (not
recommended) without these tools.
A little persuasion is needed to get the secondary sheave in
Reinstall sheave
Reinstall belt. I decided to put a new belt on.
Reinstall cage
Test before putting cover back on. Left side is low
rpm. Right side is high rpm.
Installation performed at
Hart's Rhino Motorsports
- Rancho Cordova, California (916) 635-4334.
Thanks to Paul for letting me look over his shoulder while
he worked on my Rhino.
