(2) Defective springs or rods will be replaced (pars. 65 and 67). Corrosion on the rods may be removed.

(3) For adjustment of the equilibrators, refer to paragraph 64 f and for lubrication refer to LO 9-252 or LO 9-252-1.

(4) Bent or damaged equilibrator cases will cause difficult operation and will be repaired or replaced as required (pars. 65 and 67).

(2) To correct, tighten or replace defective parts (pars. 65 and 67), lubricate (LO 9-252 or LO 9-252-1), or adjust (par. 64 f) as required.

(2) The mechanism of mount M3 does not have the lower gear; instead, the worm spacer - A338605 is mounted on the worm.

(2) Replace worn or damaged parts (pars. 70 and 74).

(3) Correct mesh between the worm and worm wheel may be obtained by installing shims of correct thickness for the worm wheel (par. 74 a).

(4) This trouble may also be caused by faulty operation of the equilibrators (par. 62), damaged trunnion bearings, or incorrect mesh between the elevating gear sector and pinion (par. 54).

(2) Check total backlash as described in paragraph 12, d and e before dismounting the mechanism. If backlash is excessive, correct by replacing worn parts (pars. 72 and 74) or by shimming (pars. 59 i and 100 k).

(2) Remove the screw which locks the gear screw and remove the gear screw (fig. 104). In some mechanisms, the screw-113626 and gear screw-A223966 are replaced by a cap screw-216971, internal teeth lock washer-111328, locking screw-112300, and gear washer-A287859 (fig. 250).

(3) Remove the hand operating sleeve, with the ring gear, from the hand operating gear (fig. 104). Do not lose the two hand operating detents and the detent spring (carriage M2A1). On some mounts M3, detents and spring are not used in the elevating mechanism; a spacer serves to keep the sleeve engaged with the inner gear. This is

(4) Remove the hand operating gear from the splined portion of the bevel gear (figs. 104 and 105).

(5) Remove the set screw from the bearing cap and remove the cap (fig. 105), using the spanner wrench - 41-W3250-242 (fig. 14).

(6) Remove the cotter pin, unscrew the gear nut, and remove washer from the bevel gear (fig. 105).

(7) Remove the bevel gear from the hand elevating housing and remove the ball bearing and gear spacer from the gear (fig. 105).

(8) Remove the other ball bearing from the housing (fig. 105).

(2) Remove the dust cap and remove the cotter pin, gear nut, and washer from the bevel gear (fig. 107). If

(3) Remove the bevel gear from the adapter housing. The inner ball bearing may come out of the housing with the gear or it may remain in the housing (fig. 107).

(4) Remove the two ball bearings (fig. 107).

(2) Mark the worm and worm wheel to indicate their relative positions.

(3) Remove the cotter pin and nut from the pinion and remove the pinion from the case, using a suitable pusher or driving it out with a wood block and hammer (fig. 108).

(4) Remove the worm wheel and the shim from the gear case (fig. 109).

(5) Remove the case plug at the side of the case and through this opening remove the set screw which locks the bearing cap (fig. 108). Remove the bearing cap (fig. 109), using the bearing cap wrench - 41-W-1977-100 (fig. 14). Remove the bearing (fig. 109).

(6) Remove the outer oil retainer if it is to be replaced (fig. 109).

(7) Remove the pinion spacer from the pinion (fig. 109).

(8) Remove the ball bearing, the bearing ring, and the inner oil retainer from the pinion, if these parts are to be replaced (fig. 109). The bearing may have remained in

(9) Remove the cotter pin, worm nut, and worm nut washer from the lower end of the elevating mechanism worm and remove the lower gear and the shim (fig. 110). In the mount M3 there is no lower gear; a spacer-A338605 is used instead.

(10) Remove the upper cover from the gear case, after removing the retaining screws with lock washers.

(11) Remove the worm by forcing it out through the upper opening in the case (field maintenance method), or using an improvised gear pusher (figs. 20 and 111) (depot maintenance method). Remove the cotter pin, worm nut, and nut washer from the upper end of the worm and remove the upper gear, the upper gear shim, and the ball bearing from the worm (fig. 112).

(12) Remove the cap screw and remove the bearing cap (fig. 112), using the tubular wrench-41-W-3736-960 with wrench handle-41-H-1549-522 (fig. 14).

(13) Remove the worm bushing with double row ball bearing, the sleeve spacer, and the worm sleeve from the lower

(2) Check all gear shafts for straightness; shafts must be straight to operate satisfactorily.

(2) Check gears for burs, chips, and cracks. Remove minor abrasions from teeth and splines; replace, if chipped or cracked.

(3) Replace detent springs, if broken. Free height of spring should be 1 5/16 inches, solid height not more than 5/8 inch, and load of 2.16 pounds minimum at 29/32 inch.

(4) Repair damaged threads.

(2) Check the bevel gear for burs, chips, and cracks. Remove minor abrasions from teeth and splines with a fine file and crocus cloth; replace, if chipped or cracked.

(3) Repair damaged threads.

(2) Inspect oil retainers for damage and replace, if necessary.

(3) Check ball bearings for rough spots, wear, and broken balls. Replace, if damaged or worn.

(4) Repair damaged threads.

(5) Examine all bearing surfaces for burs and roughness; remove minor abrasions with a fine file and crocus cloth.

(2) Install the double row ball bearing in the worm bushing (fig. 112) with the bearing numbers toward the outside or the thrust sides facing one another (fig. 112). If the bearings are assembled incorrectly, it will cause windup and backlash, particularly at low elevations where the torque is greater. If the numbers or thrust sides are not marked, assemble the bearings so that the flange sides on outer races face one another.

(3) If the oil seal was installed on the worm, install the worm sleeve in the case (fig. 112). Install sleeve spacer with beveled side down (fig. 112).

(4) Install worm bushing with bearings in lower end of case (fig. 112). Screw in bearing cap (fig. 112) with tubular wrench-41-W-3736-960 with wrench handle-41-H1549-522 (fig. 14). Lock bearing cap with lock washer and cap screw (fig. 112).

(5) Install bearing, upper gear shim, upper gear, nut washer, worm nut, and cotter pin on upper end of worm (fig. 112).

(6) Install the worm in the case, forcing it into position. If the oil seal was installed on the worm, remove the improvised spacer by withdrawing it through the worm wheel opening and tap the worm to seat it.

(7) Install the inner oil retainer ball bearing ring and the ball bearing on the wheel pinion (fig. 109).

(8) Install the. outer oil retainer and ball bearing in the case (fig. 109). Screw in cap (fig. 109) with the bearing cap wrench-41-W-1977-100 (fig. 14). Install the set screw and case plug to lock the bearing cap (fig. 109).

(9) Install the pinion spacer on the pinion and install the pinion in the case (fig. 109).

(10) Install the pinion shim and the worm wheel on the pinion (fig. 109), matching register marks on the worm and worm wheel.

(11) If a new worm wheel or worm is installed in the mechanism, it may be necessary to change the pinion shim back of the worm wheel or to fit the wheel to the worm by lapping.

(12) The worm wheel must be centered on the worm. Shims of varying thicknesses are provided to position the worm wheel. To select the correct shim proceed as follows:

(13) Tightness may be eliminated by lapping with fine lapping compound. Lap only around the high spots and, when these are eliminated, make two or three complete revolutions. After lapping, disassemble the parts and clean thoroughly to remove all traces of lapping compound.

(14) Install the wheel, worm wheel nut, and cotter pin (fig. 109).

(15) Install the lower worm gear, worm nut washer, worm nut, and cotter pin on the worm (fig. 112).

Note. For the mount M3, install the spacer-A338605 instead of the gear-B198353.

(16) Check the backlash between worm and worm wheel as follows:

(17) Install the top cover gasket and top cover, the worm wheel cover with gasket, and the lower cover or covers with gaskets. Install cover retaining screws with lock washers.

(2) Install the outer ball bearing-700917 in the adapter housing, with the seal toward the outside (fig. 107).

(3) Install the gear washer and gear nut on the bevel gear and install the cotter pin (fig. 107). If necessary, use tubular wrench-41-W -2940-8 (fig. 15) to install gear nut.

(4) Install the dust cap over the end of the gear and into the housing (fig. 107).

(5) Install the bearing adapter assembly in position, with the adapter shim between the housing and the gear case (fig. 106). Install the six cap screws with lock washers. On the mount M3, install the gasket-A338603, the cover plate-A338604, and six cap screws-216971 and lock washers-115549 instead of the power elevating mechanism. Check for binding and eliminate by lapping (a (13) above).

(6) Check backlash between worm gear and wheel and between the adapter bevel gear and worm lower gear by either of the following methods:

(2) Install the outer ball bearing in the housing, with the oil seal toward the outside (fig. 105).

(3) Install the gear washer and gear nut on the bevel gear and install the cotter pin (fig. 105).

(4) Install the bearing cap (fig. 105), using the cap spanner

(5) Install the detent spring and two hand operating detents in the hand operating gear (fig. 104). Hold the detents against spring tension, while installing the gear in the hand operating sleeve. A narrow piece of stiff paper or thin metal banding may be used to hold the detents.

Note. The detents and spring are not used in the mechanism for the mount M3.

(6) Install the gear screw at the end of the gear and install the locking screw (fig. 104). On the mount M3, install the spacer. In some mechanisms, the screw-113626 and gear screw-A223966 are replaced by a cap screw -216971, internal teeth lock washer-111328, locking screw-132300, and gear washer-A287859 (fig. 250)

(7) Mount the hand elevating mechanism in position on the gear case, with the housing shim between the housing and the elevating case (fig. 103). Check for binding and eliminate by lapping (a (13) above).

(8) To measure backlash between worm gear and wheel and between worm upper gear and hand elevating bevel gear, proceed as follows:

(2) Backlash between the worm gear and wheel can be adjusted by changing the shim between worm gear and wheel (par. 74 a (12) ).

(3) Backlash between the worm upper gear and the hand elevating bevel gear can be adjusted by changing the shim between the gear case and the hand elevating housing.

(5) Backlash at center or extremes of travel can be adjusted by changing shims between elevating gear sector and breech casing (par. 59 i).

(6) In adjusting the backlash between the gears, care must be taken not to create excessive binding. A few high spots can be eliminated by lapping around these spots and then making two or three complete revolutions. If binding is excessive, examine gears and replace, if worn or if shafts are not straight. Examine the pinion and elevating gear sector for wear as possible sources of backlash; replace if necessary. Refer also to paragraphs 59 i and 100 k for shimming the sector and top carriage trunnion bearing caps as means to reduce backlash between pinion and elevating gear sector.

(2) Lap the gears or change shims in elevating mechanism provided this does not create excessive backlash.

(2) The mechanism of the mount M3 does not have the pinion shaft bevel gear; instead the pinion shaft spacer-A338600 is used.

(2) Disconnect the clutch operating rod from the slewing clutch lever (fig. 139).

(3) Disconnect the oil gear from the platform and move it forward to disengage it from the power traversing mechanism.

(4) Disconnect the flexible shaft of the computing sight from the deflection drive assembly; the drive assembly may be removed from the top of the traversing mechanism.

(2) Secure oil gear to the platform.

(3) Secure clutch operating rod to the clutch lever. Check alinement of oil gear with a coupling gage (TM 9-252).

(4) Secure the tie bar (azimuth oil gear) to hand traversing mechanism gear case.

(5) Replace the deflection drive assembly and connect the flexible shaft of the computing sight.

(2) Remove the cotter pin, gear nut, and gear washer from the lower end of the hand traversing mechanism shaft.

(3) Drive the shaft with assembled parts out through the upper opening in the gear case, using a wood block and hammer.

(4) Remove the lower ball bearing from the gear case.

(5) Remove the cotter pin, gear nut, and gear washer from the upper end of the shaft.

Note. The traversing mechanism for the mount M3 has a cover plate-A338602 and a gasket-A338601 attached to each side opening of the gear case by means of the screws-216971 and lock washers-115549.

(2) Remove the set screw and the gear collar (fig. 122). Remove the dust cap and remove the cotter pin, gear nut, and gear washer from the bevel gear (fig. 122). If necessary, use tubular wrench-41-W-2940-8 (fig. 15) to remove gear nut. Then remove the gear and two ball bearings from the adapter (fig. 122).

(2) Remove three cap screws and lock washers from the pinion shaft bearing adapter (fig. 123). Using three

(3) Remove the lubricating fitting and the set screw from the pinion bearing cap (fig. 124).

(4) Remove the bearing cap (fig. 124), using the tubular wrench-41-W-3736-960 (fig. 14) with wrench handle -41-H-1549-522. The oil retainer may be removed from the pinion shaft bearing cap (fig. 124), if necessary.

(5) Remove the short spacer, the cotter pin, and pinion shaft nut from the upper end of the pinion shaft (fig. 124). Remove the small spacer and drive or press the pinion shaft out of the adapter (fig. 124).

(6) Remove the pinion shaft bevel gear (fig. 124) (in mount M3 a spacer-A338600 is used instead of bevel gear). Remove the oil seal, the long spacer, and the lower ball bearing from the pinion shaft (fig. 124). In mechanisms of alternate design, an oil deflector and an oil trap are used in place of the oil seal.

(7) Remove the double row ball bearing from the bearing adapter (fig. 124).

(2) Remove the gear case bolt and safety nut and cap screws with lock washers and separate the two gear cases (fig. 125).

(3) Mark the position of the spur gear on the pinion and drive the pinion the rest of the way out of the case. Remove the lower ball bearing from the pinion (fig. 125).

(4) Remove the spur gear from the pinion shaft gear case (fig. 125). Also remove the upper ball bearing from the gear case (fig. 125).

(2) Remove the coupling spacer from the coupling shaft (fig. 126).

(2) Check all gear shafts for straightness; shafts must be straight to operate satisfactorily.

(2) Check gears for burs, chips, and cracks. Remove minor abrasions from teeth and splines; replace, if chipped or cracked.

(3) Repair damaged threads.

(2) Check the bevel gear for burs, chips, and cracks. Remove

(3) Repair damaged threads.

(2) Inspect oil retainers for damage and replace, if necessary.

(3) Check ball bearings for rough spots, wear, and broken balls. Replace, if damaged or worn.

(4) Repair damaged threads.

(5) Examine all bearing surfaces for burs and roughness; remove minor abrasions.

(2) Install the coupling cover over the end of the lower coupling (fig. 126).

(2) Install the spur gear on the pinion, matching reference marks on the splines and spline ways (fig. 125). Be sure that the longer portion of the gear hub faces upward.

(3) Install the upper ball bearing in the traversing gear case and assemble the two gear cases with cap screws, lock washers, and gear case bolt with safety nut (fig. 125).

(4) Install the gear washer, gear nut, and cotter pin on the upper end of the pinion (fig. 125).

(5) Install the gear bearing cap in the traversing gear case, aline the set screw openings, and install the set screw (fig. 125).

(3) Install the pinion shaft with assembled parts in the adapter and install the small spacer, the pinion shaft nut, and cotter pin on the shaft; install the short spacer (fig. 124).

(4) If the oil retainer was removed from the pinion shaft bearing cap, install the new retainer, with the spring facing upward (fig. 124). Screw the bearing cap to the adapter (fig. 124), using the tubular wrench-41-W3736-960 (fig. 14) and wrench handle-41-H-1549-522. Aline the set screw openings and install the set screw (fig. 124). Install the lubricating fitting in the cap (fig. 124).

(5) Install the gear case shim on the traversing gear case and install the pinion shaft with assembled parts in the gear case (fig. 123). Match reference marks on the pinion shaft and the gear case and those on the pinion and pinion shaft gear case. Install the cap screws with lock washers on the bearing adapter (fig. 123), tightening the screws evenly to force the parts into the case.

(6) Install the gear case cover with screws and lock washers to bottom of pinion shaft gear case.

(7) Turn pinion shaft and test for binding.

(8) Check backlash as follows:

(2) Install the bevel gear in the bearing adapter (fig. 122).

(3) Install the gear washer, gear nut, and cotter pin on the bevel gear (fig. 122). If necessary, use tubular wrench-41-W-2940-8 (fig. 15) to install gear nut.

(4) Install the dust cap (fig. 122).

(5) Install the gear collar and set screw (fig. 122).

(7) Install the three cap screws with lock washers for the adapter assembly (fig. 121). (On the mount M3, install the two cover plates with gaskets.)

(8) Turn the bevel gears and the pinion shaft by hand and test for binding. Eliminate binding by lapping as described in paragraph 74 a (13).

(9) Check the backlash between the pinion shaft and spur gear and between the power drive bevel gear and pinion shaft bevel gear, using the method described in paragraph 74 b (6). Refer to paragraph 83 a.

(2) Install the lower ball bearing in the gear case, with the seal toward the bottom. Be careful not to damage the seal.

(3) Install the shaft with assembled parts through the upper opening in the case and tap it into position.

(4) Install the gear washer, gear nut, and cotter pin on the lower end of the shaft.

(5) Install the lower bearing cap in the gear case, aline the holes for the gear case screw, and install the screw.

(6) Install the short shaft spacer on the shaft.

(2) To check backlash between the hand traversing bevel gear and the hand traversing short bevel gear, lock the hand traversing shaft, twist the adapter one way until slack is taken up, stop, and mark the adapter and housing in line; then twist the adapter the other way until slack is taken up, stop, and mark the housing in line with the mark on the adapter; measure the peripheral distance between the two marks on the housing. (Refer to par. 83a.)

(2) A small amount of backlash may be eliminated by moving the traversing mechanism a slight amount and reaming the taper pin holes to hold the assembly in the new position. Before the taper pin holes are reamed, the precautions outlined below must be taken to prevent the chips from falling into the bearing or the entire top carriage must be removed and the bearing disassembled to clean out the chips:

(3) To reduce backlash between the pinion shaft and spur gear, replace worn gears.

(5) Backlash between the hand traversing short and long bevel gears can be reduced by changing the shim between the adapter and the case.

(6) In adjusting backlash between the gears, care must be taken not to create excessive binding. A few high spots can be eliminated by lapping. If binding is excessive, examine gears and replace, if worn or if shafts are not straight.

(2) Lap gears or change shims in traversing mechanism provided this does create excessive backlash.

(2) Structural differences of various components to adapt the linkages to the different platform frames and top carriages; these differences do not affect ordnance maintenance to any marked extent.

(2) Detach connecting link by removing cotter pin, washer, and rod end pin at front lever (fig. 131) and cotter pin and pin at rear lever (fig. 130).

(3) Detach link clevis from rear lever by removing cotter pin, washer, and pin (fig. 132).

(5) Remove the two cap screws and lock washers that secure the lever bracket to the top carriage (fig. 132); remove the lever bracket with attached parts and disassemble (fig. 132).

(2) Detach the front firing pedal with inner left footrest from the outer front link by removing cotter pin, washer, and rod end pin (fig. 133).

(3) Drive out the taper pin from the footrest shaft collar and separate the footrest and firing pedal assemblies (fig. 134); remove the two bushings from the pedal assembly, if necessary, drive out taper pin and disassemble the outer footrest assembly (fig. 134) (depot maintenance only).

(2) Disconnect the lever bracket from the top carriage and remove the firing mechanism lever and bracket (fig. 135).

(3) Remove the cartridge ejector chute cover (par. 91 c (1)) and disconnect the front links and the firing

(4) Drive out the taper pin that secures the front lever to the front lever pin and remove front lever and lever pin (figs. 131 and 135).

(5) Drive out the straight pin that secures the rod coupling to the clevis rod and remove the clevis rod (fig. 136). Turn the rod coupling up against the casing bushing and unscrew casing bushing with rod coupling, rod spring, and firing rod as a unit from rod casing. Place the rod with assembled parts in an arbor press, compress the rod spring, unscrew the rod coupling, carefully release spring pressure, and remove parts (fig. 136).

(2) Insert the rod with assembled parts into the rod casing and screw the casing bushing into the rod casing. Unscrew the rod coupling one or two turns to provide room for adjustment.

(4) Install the firing rod assembly, engaging the linkage at upper and lower ends. Connect all the links and pins.

(2) Assemble and install the left inner footrest assembly to the pedal assembly and secure by replacing shaft collar and taper pin (fig. 134). Attach the unit to the outer link by means of the rod end pin, washer, and cotter pin (fig. 134).

(3) Assemble and connect the left outer footrest assembly to the left inner footrest by means of the cap screws, lock washers, and key (fig. 133). Install left footguard.

(2) Install the rear lever (fig. 135) and secure to left stay and left support angle (fig. 137).

(3) Attach the connecting link to front and rear levers (figs. 130 and 131). Secure the upper link clevis to the rear lever by means of the pin, washer, and cotter pin (fig. 132).

(4) Secure the rear firing pedal to the connecting lever by means of the four cap screws and lock washers (fig. 130).

(2) Disconnect clutch operating rod from slewing clutch lever and remove oil gears (TM 9-1678).

(3) Remove breech casing (par. 55).

(2) Detach the connecting link and rear lever assembly from rear firing pedal mechanism (par. 86 a).

(3) Detach the connecting bar from the control lever assembly and from the mechanism handle assembly (fig. 139).

(4) Disconnect the left and right stays from chute support angles and remove the handle and stays from stay spindle (fig. 140). Disassemble the handle and stay assemblies (fig. 140) (depot maintenance only).

(5) Disconnect clutch operating rod from the slewing clutch lever (fig. 139).

(2) Disconnect the distribution box support from the chute support angles and place support and box out of the way.

(3) Remove the rear chute, rear intermediate chute, front chute, front intermediate chute and chute support angles.

(2) Remove the right footrest assemblies by disconnecting the couplings (fig. 143); do not lose the key (fig. 143).

(3) Disassemble footrests by driving out the taper pins (fig. 144) (depot maintenance only).

(4) Remove the left outer and inner footrests and front firing pedal and disassemble (par. 86 b) (depot maintenance only).

(3) Remove the loading platform from the platform frame.

(4) Remove the two platform caps and lift the platform frame.

(2) Assemble the operators' seats and install on the platform frame. Assemble the right footrests (fig. 144) and install on the platform frame by securing the couplings and the key (fig. 143).

(2) Replace the chute cover.

(3) Secure the distribution box and support to the chute support angles.

(2) Assemble the control lever assembly (fig. 142) (depot maintenance only). Test the assembled parts for end play. End play will be from a minimum of 0.004 inch to a maximum of 0.008 inch. If end play is too little, machine the ends of the bearing to give sufficient end play. If excessive, replace necessary parts.

(3) Position the rod pin of the operating rod in the upper hole of the outer lever of the control lever assembly and secure with a washer and cotter pin. Secure the control lever assembly to the azimuth switch bracket (fig. 139).

(4) Assemble the mechanism handle (fig. 140). Assemble the right stay assembly, if disassembled. Secure the stay spindle to the bracket on the rear chute and attach the handle and the stays to the spindle. Connect the front end of the stays to the chute support angles.

(5) Attach the connecting bar to the handle and to the inner lever of the control lever assembly.

(6) Secure connecting link and rear lever assembly to rear firing pedal mechanism (par. 88 c).

(7) Secure azimuth limit switch assembly to the switch bracket (fig. 139) and connect the cables.

(2) Install the breech casing (par. 56).

(3) Connect the cables to all switches, oil gears, and motors, contact ring, and distribution box.

(2) Elevating mechanism (par. 70).

(3) Traversing mechanism (par. 78).

(4) Top carriage firing linkage (par. 86).

(5) Elevation limit switch and elevation switch (carriage M2A1) (TM 9-1678).

(2) Remove the cotter pin and nut from the upper end of the contact ring plug.

(3) Working from the under side of the chassis, remove the eight retaining screws with washers from the bottom chassis plate and remove the plate.

(4) Remove the contact ring plug, carefully pulling it straight down from the receptacle. Wrap the plug in clean" cloth or paper to protect it from dirt or damage while it is removed. Do not remove the cable assembly from the plug.

(5) Remove retaining screws and washers and remove contact ring receptacle.

(2) Unwrap the contact ring plug. Be sure that it is thoroughly clean and install it in the receptacle, working it carefully into position. Avoid damaging the spring brushes in the receptacle. Install the nut and cotter pin on the upper end of the contact ring plug.

Caution: Do not screw nut down too far as it may cause the spindle to bind and shear off.

(3) Install the cap and gasket with four screws and lock washers over the end of the plug.

(4) Install the chassis bottom plate, with the notch in the bracket engaged with the lug on the contact ring plug. Install the plate retaining screws with lock washers.

Note. The mount M3 has no contact ring assembly; cover the opening in top carriage with gasket and plate (fig. 145).

(2) Top carriage firing linkage (par. 88).

(3) Traversing mechanism (par. 79).

(4) Elevating mechanism (par. 71).

(5) Frame platform group (par. 94 or 95).

(2) Accurately center the cross level vial by means of the outrigger jacks and traverse the gun 180°. Correct half the vial error by shimming the low end of the vial casing. Recheck at 180° and again correct, if necessary, using the same procedure.

(3) When vial is level at 180° intervals, traverse 90° and

(4) The carriage is now leveled so that the longitudinal vial may be adjusted to level by use of shims with the top carriage in any position. Recheck both vials at 90° intervals.

(2) If elevation readings indicated by the pointer vary from those of the quadrant, tap the pointer with a hammer to move it the necessary amount.

(2) If adjustment is necessary, remove trunnion bearing caps, raise gun with a sling and hoist high enough to permit removal of trunnion bearing (fig. 150) and apply the shimming corrections (par. 100 k).

(3) Repeat the above tests and make any required changes in shims to insure satisfactory operation.