TM 9-2520-246-34 CHAPTER 5 REPAIR OF POWER TAKEOFFS Section I. DESCRIPTION, OPERATIONAL AND DATA (MODEL WN-7-28) 5-1. General. This chapter contains the rebuild instructions for power takeoff models WN-7-28, WND-7-28, and P-136-C. 5-2. Description (Figure 5-1). Heavy-duty power takeoff model WN-7-28, is designed for mounting on an SAE standard 6-hole or 6-stud power takeoff opening. The unit is designed to be mounted on the left or right side of the driving mechanism. The shifter shaft extends through each end of the case so that the shifting control linkage may be attached at either end. The output shaft extends from the front of the case and is provided with a woodruff key for mounting the winch propeller shaft companion flange. Boots are installed over the ends of the shifter shaft to protect the surface of the shaft. The input gear of the power takeoff is a cluster composed of a helical gear which is constantly in mesh with the helical gear of the transmission reverse idler gear, and the driving gear which is of spur tooth construction. The power takeoff has two speeds forward, neutral, and one speed in reverse. A shifting mechanism provides for selection of the desired speed and direction of rotation of the output shaft. The shifting mechanism in neutral position disengages the output shaft gears from the driving gear. 5-3. Operation. NOTE The reference letters in parentheses pertain to figure 5-2. a. Input Gear. The helical input gear (P) is in constant mesh with the helical gear of the transmission reverse-idler gear and therefore, is in constant rotation when the transmission is engaged. (Refer to transmission, Chapter 3.) The input gear (P) is installed on a nonrotating input gearshaft (L) and is mounted on the input gear roller bearings (N). The shaft is pressed into the housing and secured with a cotter pin. A thrust washer (M) is located at each end of the input gear. The helical tooth portion of the input gear (P) is in constant mesh with the reverse gear (FF) which is installed on the reverse gearshaft (JJ) and secured with the reverse gear pin (EE). The reverse gearshaft rotates in two supporting bearings (GG and FF). b. Output Shaft. The output shaft (H) is supported in the housing on two ball bearings (F and S). Two gears are installed on the output shaft (H). One is the output shaft sliding gear (AA) which is moved forward and backward on the shaft by the shifter fork (Z). The other is the output shaft high speed gear (BB) which is free on the output shaft (H) and is in constant mesh with the input gear (P). The sliding gear (AA) is splined to the output shaft (H) and may be meshed with the spur teeth of the reverse gear (FF), with the spur teeth of the input gear (P) (for low speed operation) or may act as a clutch gear to couple the output shaft high speed gear (BB) to the output shaft (H). c. Shifter Fork. The shifter fork (Z) is attached to the shifter shaft (A) by a capscrew. The fork engages the circumferential groove on the sliding gear (AA). Figure 5-1. Power Takeoff Model WN-7-28. 5-4. Data. National stock number . . . . . . . . . . 252040-7061137 Ordnance number . . . . . . . . . . . . . . . . . . . . . . . 7061137 Manufacturer . . . . . . . . . . . Spicer Div. - Dana Corp. Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WN-7-28 Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heavy-duty Speeds . . . . . . . . . . . . . . . . . . . . . . 2 forward, 1 reverse Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transmission Input gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Helical Output shaft . . . . . . . . . . . . . . . . . 1ΒΌ in. dia;5/16 in. keyway Bearings: Output shaft . . . . . . . . . . . . . . . . . . . Two-ball type Input shaft . . . . . . . . . . . . . . . . . . . . Two-roller type Reverse gear . . . . . . . . . . . . . . . . . . Two-roller type Horsepower delivered: 100 rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 500 rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1000 rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Gear pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7/9 in. Backlash (allowable) . . . . . . . . . . . . . . . . . . . . 0.008 in. 5-1