The A-250 is a three speed transmission equipped with a synchronizer between second and third gears. Lubricant capacity is 4 1 / 2 pints.
See Figure 1
- Remove case cover and gasket.
- Measure the synchronizer "float" with a pair of feeler gauges. Measurement is made between the synchronizer outer ring pin and the opposite synchronizer outer ring. This measurement must be made on two pins 180 degrees apart with equal gap on both ends for "float" determination. The measurement should be between 0.060-0.117". A snug fit should be maintained between feeler gauge and pins.
- Remove the bolt and retainer holding the speedometer pinion adapter in the extension housing. Carefully work the adapter and pinion out of the extension housing.
- Remove extension housing bolts and extension housing.
- Remove the bolts that attach the drive pinion bearing retainer to case, then slide the retainer off the pinion. Pry the seal out of retainer using a screwdriver. Be cautious not to nick or scratch the bore.
- Rotate the drive pinion so that the blank clutch tooth area is opposite the countershaft for removal clearance.
- Slide drive pinion assembly slightly out of case. Move the synchronizer front inner stop ring from the short splines on the pinion shaft. Slowly remove drive pinion assembly.
- Remove snapring that holds bearing on pinion shaft. Remove pinion bearing washer. Using an arbor press, press pinion shaft out of bearing. Remove oil slinger.
- Remove snapring and bearing rollers from the end of the drive pinion.
- Remove clutch gear retaining snapring from the mainshaft.
- Remove the mainshaft bearing securing snapring from case.
- Slide mainshaft and bearing rearward out of case while holding the gears as they drop free.
- Remove the snapring from mainshaft and press the bearing off of mainshaft.
- Remove the synchronizer components, second gear, first/reverse gear and shift forks from case.
Steps 15 thru 18 need only be performed if gear shift lever seals are leaking.
- Remove the shift levers from the shift shafts.
- Drive out the tapered retaining pin from the first/reverse shift shaft. Remove the shift shaft from inside the case. As the detent balls are spring loaded, when the shafts are removed the balls will drop to the bottom of the transmission case.
- Remove the interlock sleeve, spring and both detent balls from case. Drive tapered retaining pin out of second/third shaft and remove shaft from case.
- Drive shift shaft seals out of case with a suitable drift.
- Check end-play of countershaft gear with a feeler gauge. The end-play should be between 0.005-0.022". This measurement is used to determine if a new thrust washer is necessary during reassembly.
- Using a countershaft bearing arbor, drive the countershaft towards the rear of the case until the small key can be removed from the countershaft.
- Drive the countershaft the rest of the way out of the case, keeping the arbor tight against the end of the countershaft. This will prevent loss of roller bearings.
- Remove the countershaft gear, front thrust washer and rear thrust washer from the case.
- Remove the bearing rollers, spacer ring and center spacer from the countershaft gear.
- Drive the reverse idler gear shaft out of the transmission case using a suitable drift. Remove the Woodruff key from the end of the reverse idler shaft.
- Remove the reverse idler gear and thrust washers out of the case. Remove the bearing rollers from the gear.
See Figure 2
- Slide the countershaft gear bearing roller spacer over arbor tool. Coat the bore of gear with lubricant and slide tool and spacer into gear bore.
- Lubricate the bearing rollers with heavy grease and install two rows of 22 rollers each in both ends of gear in area around arbor. Cover with heavy grease and install bearing spacer rings in each end of gear and between roller rows.
- If countershaft gear end-play was found to be excessive during disassembly, install new thrust washers. Cover with heavy grease and install thrust washer and thrust needle bearing and cap at each end of countershaft gear and over arbor. Install gear and arbor in the case, and make sure that tabs on rear thrust washer slide into grooves in the case.
- Drive the arbor forward out of the countershaft gear and through the bore in the front of the case using the countershaft and a soft faced hammer. When the countershaft is almost in place, make certain the keyway in the countershaft is aligned with the key slot in the rear of the case. Insert the shaft key and continue to drive the countershaft into the case until the key is bottomed in the slot.
- Position special arbor tool in the reverse idler gear and install the 22 roller bearings using a heavy grease.
- Place the front and rear thrust washers at each end of the reverse idler gear. Position the assembly in the transmission case with the chamfered end of the gear teeth towards the front. Make sure that the thrust washer tabs engage the slots in case.
- Insert reverse idler shaft into the bore at rear of case with keyway to the rear, pushing the arbor towards the front of the case.
- When the keyway is aligned with the slot in the case, insert the key in the keyway. Drive the shaft forward until the key is seated in the recess.
Steps 9 through 14 need only be performed if the shift levers have been disassembled.
- Place new shift shaft seals in the case and drive it into position with suitable drift.
- Carefully slide the first/reverse shift shaft into the case and lock into place with a tapered retaining pin. Position the lever so that the center detent is aligned with the interlock bore.
- Install the interlock sleeve into the bore followed by a detent ball, spring and pin.
- Install remaining detent ball and hold in place with detent ball holding tool.
- Depress the detent ball and carefully install the second/third shift shaft. Align center detent with detent ball and secure lever with tapered retaining pin.
- Install shift levers and tighten retaining nuts to 18 ft. lbs.
- Press the bearing on the mainshaft and select and install snapring that gives minimum end-play.
- Move shift lever to reverse position, and then place the first/reverse gear and shift fork in the case.
Both shift forks are offset toward the rear of the transmission case.
- Assemble the synchronizer parts with shift fork and second gear.
- Place the second gear assembly in the transmission case and insert the shift fork into its lever.
- Install the mainshaft carefully through the gear assembly until it bottoms in rear of case.
- Install synchronizer clutch gear snapring on mainshaft.
- Select and install mainshaft bearing snapring in case.
- If "float" measurement was found to be above or below 0.117", install or remove shims to place "float" within range.
- Install oil slinger on drive pinion shaft and slide against the gear.
- Slide the bearing over the pinion shaft with snapring groove away from gear, then seat bearing on shaft using an arbor press.
- Install keyed washer between bearing and retaining snapring groove.
- Secure bearing and washer with selected thickness snapring. If large snapring around bearing was removed, install it at this time.
- Place drive pinion shaft in a vise with soft faced jaws and install the 14 roller bearings in the shaft cavity. Coat the roller bearings with a heavy grease and install retaining ring in groove.
- Rotate the drive pinion so that the blank clutch tooth area is next to the countershaft. Guide the drive pinion through the front of case and engage the inner stop ring with the clutch teeth. Then seat pinion bearing. The pinion shaft is fully seated when the snapring is in full contact with the case.
- Install a new seal in the pinion bearing retainer.
- Position retainer assembly and new gasket on the case. Use sealing compound on bolts and tighten to 30 ft. lbs.
- Slide the extension housing and a new gasket over mainshaft. Guide shaft through bushing and oil seal. Use sealing compound on the bolt used in the hole tapped through the transmission case. Install remaining bolts and tighten all to 50 ft. lbs.
- Install the transmission cover and gasket and tighten cover bolts to 12 ft. lbs.
- Rotate the speedometer pinion gear and adapter assembly so that the number on the adapter corresponding to the number of teeth on the gear is in the 6 o'clock position as the assembly is installed.
- Fill the transmission with the proper lubricant and install the drain plug and tighten to 25 ft. lbs. Install the back-up light switch and tighten to 15 ft. lbs.
- Rotate the drive pinion shaft and check operation of transmission by running the transmission through all gear ranges.