Steer Planetary Gearing, Left and Right

TM 9-2520-249-34&P

b. Operation.

When the steer clutch is

stationary cam (35) have matching, inclined pockets

(cams). Twelve steel balls (43) are installed in these

applied, it prevents rotation of the output clutch housing

pockets and separate the stationary and rotating cams.

assembly (19, FO-7). The steer planetary sun gear,

Thus, when cam (42) rotates, the steel balls ride up the

being integral with the housing, is also stopped.

inclined pockets and force the rotating cam away from

Rotation of the ring gear (splined to the reverse range

the stationary cam.

sun gear, which is driven by the cross shaft) causes

(3) The outward face of the rotating cam

pinions (60.3, FO-6) to rotate about the stationary sun

compresses apply disk (2, FO-7) and brake disks (3 and

gear. Thus, the torque imparted by the rotating ring

4) against reaction plate assembly (5). The resulting

gear is transferred through the pinions to the carrier

friction between the plates causes internal-splined disks

which is splined to the output shaft.

The speed

(3) to rotate slower or stop This action slows or stops

reduction obtained through this gearing is a ratio of

brake hub (45, FO-6) which is splined to steer planetary

1.478 to 1. In addition to its primary function, the steer

carrier (58). The steer planetary carrier is splined to the

planetary gearing also functions as a reduction gear

output shaft. Thus, when the brakes are applied, the

during straight travel in first gear.

rotation of the output shaft is slowed or stopped.

(4) Simultaneously with application of the

2-15.

Steer Clutches, Left and Right

brake, lever (86, FO-13) is lifted off signal valve (95)

a. Description.

and hydraulic pressure closes brake air valve assembly

NOTE

(76). When closed, no air is admitted to the intake for

The left steer clutch (FO-7) and the right

the brake coolant pump, and the pump supplies coolant

steer

clutch

(FO-8)

are

identical.

to the applied brakes. When the brake is released, air is

Therefore, description of one clutch will

supplied to the pump intake and no coolant is pumped.

serve to describe the other.

The

Air valve assembly (76) is also actuated by a signal

description below is keyed to foldout 7,

pressure during steer, causing coolant to flow to the

the left steer clutch.

clutches used for steer.

(1) The steer clutch includes piston (35,

FO-7), apply disk (16), four external-tanged disks (12),

2-14.

Steer Planetary Gearing, Left and Right

and four internal-splined disks (14). Anchor pins (6)

a. Description.

engage the external-tanged disks. Guide pins (15) and

NOTE

springs (13) complete the assembly. (Anchor pins (6),

The left steer planetary gearing (FO-6 and

guide pins (15) and springs (13) also serve the brake

-7) and right steer planetary gearing (FO-8

assembly).

and -9) are identical.

Therefore,

(2) Piston (35, FO-7) travels in a bore,

description of one planetary will serve to

machined in output housing (55). Disks (12 and 14),

describe the other.

The description

apply disk (16), guide pins (15), and springs (13) are

below is keyed to foldouts 6 and 7, the

assembled to reaction plate assembly (5) which is bolted

output housing (55). External tanged disks (12) are held

left steer planetary.

stationary by anchor pins (6). Internal-splined disks (14)

(1) The steer planetary gearing includes

are assembled alternately between disks (12), and

three main elements: sun gear, ring gear, and planetary

engage the splines on output clutch housing assembly

carrier assembly. An 8-pitch, 32-tooth sun gear (integral

(19).

with output clutch housing assembly 19, FO-7) is the

b. Operation.

reaction element. A 67-tooth ring internal gear (49,.

(1) When the steer clutch is applied,

FO-6), which is splined to reverse range sun gear

hydraulic pressure pushes piston (35, FO-7) toward

assembly (47, is the driving element. Planetary carrier

steer clutch disks (12 and 14). The disks compress

(58), the driven element, contains six, 17-tooth pinions

against reaction plate assembly (5) and friction prevents

(60.3) which rotate on pinion rollers (60.4) placed

rotation of internal-splined disks (14). This, in turn,

between the pinions and spindles (60.8). Spacers (60.2

prevents rotation of output clutch housing assembly (19)

and 60.5) position rollers (60.4). Thrust washers (60.1

and the attached steer planetary sun gear. Thus, when

and 60.6) position pinions (60.3) and absorb end-thrust

the steer planetary sun gear is stopped, a reduction in

forces. Spindles (60.8) are pressed into the carrier and

speed occurs, as described in paragraph 2-14b.

locked in place with pins (60.7).

(2) Either of two steer systems may be

(2) Planetary carrier (58, FO-6) is

selected-normal for land, or pivot for water. In normal

engaged by the splines on the output shaft and also by

steer (in any gear), one steer clutch is engaged, while a

the splines on the outward end of brake hub (45). An oil

reverse or output clutch is engaged in the opposite side

baffle (59) and an oil collector (56), retained by six bolts

of the transmission. In pivot steer, a steer clutch is

(57), complete the carrier assembly.

applied only in first, fourth, or reverse gear, while a

2-6