7.2TRANSMISSION
POWER FLOW
See Figure 7-1. The 6-speed transmission consists of two
parallel shafts supporting six gears each. The longer, or
mainshaft (7), also supports the clutch and serves as the input
shaft.The shorter shaft is called the countershaft (8).
Each gear on the mainshaft is in constant mesh with a corres-
ponding gear on the countershaft. Each of these six pairs of
gears makes up a different speed in the transmission.
The transmission gears are divided into two types, gears that
rotate with the shaft, and freewheeling gears that ride on
bearings and spin freely on the shaft. A gear that rotates with
the shaft always meshes with a freewheeling gear. Also, three
dog rings are able to slide sideways on the shaft. These dog
rings are used to change transmission speeds. The dogs, or
projections, on the sides of the dog rings, engage dogs on
adjacent freewheeling gears, transmitting power through the
transmission.
Gear shifting is accomplished by three forks which fit into
grooves machined into the dog rings that slide on the guide
hubs.The position of the shifter forks is controlled by a drum-
shaped shifter cam located in the transmission side door.
Neutral
Power is introduced to the transmission through the clutch. In
neutral, with the clutch engaged, the mainshaft 1st, 2nd, 3rd
and 4th gears are rotating, but no power is transferred to the
countershaft since countershaft 1st, 2nd, 3rd and 4th gears
are freewheeling gears.
1st Gear
When the transmission is shifted into first gear, the dog ring
between countershaft 1st and 2nd, which rotates with the
countershaft, engages countershaft 1st, which has been spin-
ning freely on the countershaft driven by mainshaft 1st.
Now countershaft 1st is no longer freewheeling, but locked to
the countershaft causing the countershaft and countershaft
6th to turn. Countershaft 6th transmits the power to the main
drive gear and the sprocket as shown (1).
2nd Gear
Second gear is engaged when the dog ring between counter-
shaft 1st and 2nd is shifted out of countershaft 1st and engages
countershaft 2nd. This locks countershaft 2nd to the counter-
shaft to complete the power flow as shown (2).
3rd Gear
Two shifter forks are used to make the shift from second to
third. One fork moves the dog ring between countershaft 1st
and 2nd to its neutral position, while another fork engages the
dog ring between countershaft 3rd and 4th with countershaft
3rd.This locks countershaft 3rd to the countershaft to complete
the power flow as shown (3).
4th Gear
Fourth gear is engaged when the dog ring between counter-
shaft 3rd and 4th is shifted out of countershaft 3rd and engages
countershaft 4th.This locks countershaft 4th to the countershaft
to complete the power flow as shown (4).
5th Gear
Two shifter forks are used to make the shift from fourth to fifth.
One fork moves the dog ring between countershaft 3rd and
4th to its neutral position, while another fork engages the dog
ring between mainshaft 5th and 6th with mainshaft 5th. This
locks mainshaft 5th to the mainshaft to complete the power
flow as shown (5).
6th Gear
The shift from fifth to sixth gear occurs when the dog ring
between mainshaft 5th and 6th is shifted out of mainshaft 5th,
and is shifted directly into the main drive gear (6th gear). The
main drive gear is locked to the mainshaft resulting in a direct
one-to-one drive ratio from the clutch to the sprocket as shown
(6).
7-2 2008 Dyna Service: Transmission
To Next Page
Loading...