Transmission Case
DISASSEMBLY STEPS
Note: The following "Steps" actually refer to parts in the figure above. Isuzu uses this figure and the "Steps" for disassembly and assembly.
1. Offset lever roll pin
2. Extension housing assembly
3. Offset lever, detent ball and spring
4. Oiling funnel
5. Shift cover assembly
6. 5-R Shift lever clip
7. 5-R lever pivot bolt
8. 5-R shift lever
9. 5th synchronizer snap ring, 5th synchronizer, 5th shiftfork and rail
10. 5th drive gear and 5th synchronizer blocking ring
11. Slip yoke seal, snap ring, speedometer drive gear and clip, and 5th driven gear snap ring
12. Input shaft bearing retainer, bearing outer race and shim(s)
13. Input shaft assembly
14. 3-4 gear blocking ring, mainshaft thrust bearing and race, mainshaft needle bearing (15 rollers) and spacer
15. Mainshaft rear bearing outer race
16. Mainshaft assembly
17. Reverse fork and spring
18. Counter shaft rear bearing retainer and shim
19. Reverse idler shaft roll pin, reverse idler shaft, reverse idler gear and O-ring
20. Counter shaft rear bearing outer race
21. Counter shaft rear bearing
22. Counter shaft assembly
23. Transmission case
REASSEMBLY STEPS
Note: The following "Steps" actually refer to parts in the figure above. Isuzu uses this figure and the "Steps" for disassembly and assembly.
23. Transmission case
22. Counter shaft assembly
21. Counter shaft rear bearing
20. Counter shaft rear bearing outer race
19. Reverse idler shaft, reverse idler gear, O-ring and reverse idler shaft roll pin
18. Counter shaft rear bearing retainer and shim
17. Reverse fork and spring
16. Mainshaft assembly
15. Mainshaft rear bearing outer race
14. 3-4 gear blocking ring, mainshaft thrust race and bearing, mainshaft needle bearing (15 rollers) and spacer
13. Input shaft assembly
12. Input shaft bearing retainer and bearing outer race
10. 5th drive gear and 5th synchronizer blocking ring
9. 5th synchronizer, 5th synchronizer snap ring and 5th shift folk and rail
4. Oiling funnel
8. 5-R shift lever
7. 5-R lever pivot bolt
6. 5-R shift lever clip
11. 5th driven gear snap ring, slip yoke snap ring, speedometer drive gear and clip
5. Shift cover assembly
3. Offset lever, detent bell and spring
2. Extension housing assembly
1. Offset lever roll pin
12. Input shaft bearing retainer, bearing outer race and shim(s)
DISASSEMBLY
Preparation:
- Clean the exterior of the unit with solvent.
- Remove the clutch release bearing and shift fork.
- Remove the 4 bolts that hold the clutch housing to the case, using a T50 bit.
- Mount the transmission in the holding fixture.
Install the transmission with its holding fixture into the base mounted on the end of a work bench.
Holding fixture: J-36842
Holding fixture base: J-3289-20
- Remove the drain plug from the transmission case and drain the lubricant.
- Remove the speedometer driven gear assembly, using a 10 mm wrench to remove the clamp bolt.
Pull out the sleeve/gear.
1. Offset lever roll pin
- Position the offset lever in the "3-4" neutral position.
NOTE: Removal of the offset lever in a position other than "3-4" may result in driving a roll pin into the detent/guide plate without releasing the lever from the shift shaft. Further disassembly will be difficult if this occurs.
- Using a 3/16-inch diameter pin punch and a hammer, remove the roll pin attaching the offset lever to the shift shaft.
2. Extension housing assembly
3. Offset lever, detent ball and spring
- Remove the 8 bolts that hold the extension housing to the case, using a 15 mm wrench. Note that two bolts use sealer.
- Separate the extension housing from the case and shift cover. The offset lever will also separate from the shift shaft.
NOTE: Do not attempt to remove the offset lever while the extension housing is still bolted to the case. The lever has a positioning lug which engages the detent/guide plate and prevents moving the lever far enough to remove it.
- Remove the offset lever from the extension housing, along with the detent ball and spring.
- Remove the roll pin from either the offset lever or extension housing.
4. Oiling funnel
- Carefully pry the oiling funnel from the rear of the counter shaft. This may be a very snug fit, and the funnel may become damaged.
5. Shift cover assembly
- Remove the 10 bolts that hold the shift cover to the case, using a 10 mm wrench.
NOTE: Two of the shift cover bolts are also alignment dowels. Note the location of these bolts for assembly.
- Remove the shift cover from the case by sliding it sideways toward the drain plug side of the case for a distance of 1 inch. Then lift the cover straight up from the case. You may need to break the sealer bond between the cover and case before you can separate the two.
6. 5-R shift lever clip
- Remove the 5-R shift lever clip, using a pair of needle nose pliers.
7. 5-R lever pivot bolt
- Remove the 5-R lever pivot bolt, using a T-50 bit and ratchet. Note that this bolt uses sealer.
8. 5-R shift lever
- Using a 22 mm wrench, remove the back-up lamp switch from the 5-R shift lever side of the case. Note that the threads use sealer.
- Lift the 5-R lever out of the transmission case.
9. 5th synchronizer snap ring, 5th synchronizer, 5th shift fork and rail
- Remove the 5th synchronizer snap ring from the rear of the counter shaft, using a pair of snap ring pliers.
- Remove the 5th synchronizer assembly, together with its fork/rail assembly, from the counter shaft.
10. 5th drive gear and 5th synchronizer blocking ring
- Remove the 5th drive gear and blocking ring from the counter shaft.
11. Slip yoke seal, snap ring, speedometer drive gear and clip, and 5th driven gear snap ring.
- Remove these parts from the mainshaft.
Gear puller: J-8433
Speed drive gear puller: J-38878
12. Input shaft bearing retainer, bearing outer race and shim(s)
- Scribe alignment marks on the case and input bearing retainer and remove the four input shaft bearing retainer bolts, using a 13 mm wrench. Note the thread sealer on these bolts.
- Remove the input bearing retainer, together with the bearing outer race and shim(s).
13. Input shaft assembly
- Remove the input shaft from the case by rotating it until the flat surface on the clutch tooth ring on the shaft allows it to clear the counter shaft.
14. 3-4 gear blocking ring, mainshaft thrust bearing and race, mainshaft needle bearing (15 rollers) and spacer
- Remove these parts, either from the input or mainshaft.
15. Mainshaft rear bearing outer race
- Push the mainshaft rearward to remove the rear bearing outer race.
16. Mainshaft assembly
- Tilt and lift the mainshaft from the case.
17. Reverse fork and spring
- Remove the reverse fork and spring from the case.
18. Counter shaft rear bearing retainer and shim
- Remove the counter shaft rear bearing retainer by:
- Bending back the lock tabs with a punch and hammer.
- Removing the four bolts, using a 13 mm wrench, or T-40 bit and ratchet.
- Removing the retainer and shim from the case.
19. Reverse idler shaft roll pin, reverse idler shaft, reverse idler gear and O-ring
- Remove the roll pin that holds the reverse idler shaft in the case, using a 3/16-inch diameter pin punch and a hammer.
- Remove the reverse idler assembly by pushing the shaft rearward and out of the case. Lift the reverse idler gear and O-ring out of the case.
20. Counter shaft rear bearing outer race
21. Counter shaft rear bearing
- Remove the rear bearing outer race by pushing it rearward. Remove the rear bearing assembly from the counter shaft by using a special puller and split plate.
Gear puller: J-8433
Bearing and gear puller: J-22912-01
22. Counter shaft assembly
- Remove the counter shaft as shown in.
23. Transmission case
INSPECTION AND REPAIR
1. Clean all parts with solvent and dry them with compressed air.
2. Inspect these parts for cracks and damaged sealing surfaces.
- Case
- Extension housing
- Shift cover
- Input bearing retainer
- Counter shaft rear bearing retainer
Use a fine mill file to dress minor scratches or burrs.
Replace severely damaged parts. Replace the counter shaft rear bearing retainer if the tangs are broken.
3. Look at surfaces on the above parts which support bearings and shafts. Replace parts which have excessive wear in these areas. Do not replace gears if phosphate coatings are worn.
4. Examine the bearing surfaces of the following parts:
- Input shaft
- Mainshaft and its gears
- Counter shaft and the fifth drive gear
- Reverse idler shaft and its gear
Replace parts which show signs of excessive wear. Do not file surfaces which have been hardened and precision ground.
5. Inspect shift mechanism parts as follows:
- Look for wear on the shift shaft.
- Look at the detent/guide plate and offset lever for worn edges or grooves where the detent ball and lug travel.
- Look for worn edges on these parts:
- Selector arm
- Interlock plate
- Selector plates for the 1-2 and 3-4 shift forks
- 5-R shift lever and the rollers on the reverse fork and the 5th shift rail/fork
- Look for worn mating surfaces on the following parts:
- 1-2 shift fork, pads and synchronizer sleeve
- 3-4 shift fork, pads and synchronizer sleeve
- 5th shift rail/fork, pads and synchronizer sleeve
- Reverse fork and the mating sleeve surface of the reverse idler gear.
6. Inspect the following bearings for excessive wear:
- Crankshaft pilot bushing for the front of the input shaft
- Clutch release bearing
- Input shaft bearing
- Mainshaft pilot bearing rollers
- Mainshaft thrust bearing and its mating surfaces
- Speed gear roller bearing on the mainshaft
- Mainshaft rear bearing
- Counter shaft front and rear bearings
Replace any bearing and its races that show roughness.
7. Inspect the gear tooth surfaces on all the gear sets. Replace all mating gears in a set if any one has excessive wear on the meshing surfaces of its teeth. Look for fractures, pitting, scoring and galling.
8. Disassemble the three synchronizer assemblies:
- The 1-2, which has three-piece assemblies.
- The 3-4, which has sintered metal blocking rings.
- The 5th, which uses a single piece brass blocking ring.
- Examine the fit between the hub and sleeve of each synchronizer.
Besides binding shift linkage, an excessively tight or loose hub-to-sleeve fit will cause what is known as a "hard shift."
Blocking Ring To Gear Clearance (standard):
- Measure the clearance between the blocking ring and the speed gear.
Replace components if not within specifications shown.
Excessive wear on either the blocking ring or the speed gear cone surface will cause "shift block-out" or "gear clash."
- Look for evidence of gear clash on both the synchronizer sleeve teeth or the clutch teeth on the speed gear. Finally, look at the synchronizer sleeve and speed gear clutch tooth area for cause of "hop-out".
REASSEMBLY
Note: The following "Steps" actually refer to parts in the figure above. Isuzu uses this figure and the "Steps" for disassembly and assembly.
23. Transmission case
22. Counter shaft
21. Counter shaft rear bearing
- Use a hydraulic press and the J-6133-01 installer to press the counter shaft rear bearing assembly onto the shaft. Use tool J-37357 to support the counter shaft in the case.
Installer: J-6133-01
Installer: J-37357
20. Counter shaft rear bearing outer race
SHIM ADJUSTMENT (COUNTER SHAFT END PLAY)
- Install the counter shaft rear bearing outer race and retainer without the shim.
- Tighten the retainer bolts, using a 13 mm socket (or a T-40 bit) and a torque wrench.
Torque: 20 N-m (15 lb-ft)
- Mount a dial indicator on the case and set it up to measure counter shaft end play. Move the counter shaft up and down and read the total amount of indicator travel.
- Select a shim which is the same thickness as the indicator reading, or up to 0.004 inch less than the reading.Application and ID
- Remove the counter shaft rear bearing retainer and outer race.
19. Reverse idler shaft, reverse idler gear, O-ring and reverse idler shaft roll pin
- Install the reverse idler shaft, gear, and O-ring. Use a 3/16 inch diameter pin punch and hammer to install the reverse idler shaft roll pin.
18. Counter shaft rear bearing retainer and shim
- Install the counter shaft rear bearing outer race, shim and retainer.
- Tightening the bolts.
Torque: 20 N-m (15 lb-ft)
- Bend the lock tabs on the retainer, using a punch and hammer.
17. Reverse fork and spring
- Install the reverse fork and spring.
16. Mainshaft assembly
- Install the mainshaft assembly into the case.
15. Mainshaft rear bearing outer race
- Install the mainshaft rear bearing outer race into the rear of the case.
14. 3-4 gear blocking ring, mainshaft thrust race and bearing, mainshaft pilot bearing rollers and spacer
- Install 4th speed blocking ring onto the front of the mainshaft.
- Install the mainshaft thrust race, bearing, and spacer onto the front of the mainshaft.
- Apply petroleum jelly to the mainshaft pilot bearing rollers (there are 15 rollers) and install them into the input shaft.
13. Input shaft assembly
- Install the input shaft onto the front of the mainshaft.
12. Input shaft bearing retainer and bearing outer race
- Install the input bearing retainer and outer race without shim onto the front of the case.
- Tighten the four bolts, using a 13 mm socket and a torque wrench.
Torque: 20 N-m (15 lb-ft)
10. 5th speed drive gear and 5th synchronizer blocking ring
- Install the 5th speed drive gear and its blocking ring on the rear of the counter shaft.
9. 5th synchronizer, 5th synchronizer snap ring and 5th shift fork and rail
4. Oiling funnel
Assemble the 5th synchronizer and rail/fork and install them:
- Guide the rail through the reverse fork and spring and into the front of the case.
- Push the synchronizer assembly onto the splines of the counter shaft.
- Install the 5th synchronizer snap ring and oiling funnel.
8. 5-R shift lever
- Install the 5-R lever into the case.
Align the slots of the lever with the rollers of the reverse fork and 5th shift rail.
7. 5-R lever pivot bolt
- Coat the threads of the 5-R lever pivot bolt with sealer and install it into the case. Make sure that the 5-R lever is properly aligned with the pivot bolt.
- Tighten the pivot bolt, using T-50 bit and a torque wrench.
Torque: 27 N-m (20 lb-ft)
6. 5-R shift lever clip
- Install the 5-R lever clip, using a pair of needle nose pliers.
- Use a pair of needle-nose pliers to attach the reverse fork spring to its pin inside the case.
Check the operation of the 5-R shift mechanism at this time.
11. 5th driven gear snap ring, slip yoke snap ring, speedometer drive gear and clip
- Install the 5th driven gear snap ring, using snap ring pliers.
- Install the speedometer drive gear onto the rear of the mainshaft, using installer and a hammer. Be sure the speedometer gear retaining clip is fully seated.
Installer: J-6133-01
- Install the slip yoke snap ring onto the end of the mainshaft, using a pair of snap ring pliers.
5. Shift cover assembly
- Apply a 3 mm (1/8 in.) bead of RTV sealant on the sealing surface of the shift cover.
- Make sure that the 1-2 and 3-4 synchronizer sleeves are in Neutral position, as well as the 5-R shift lever.
- Lower the cover onto the case, allowing the 1-2 and 3-4 forks to slide onto their sleeves. Slide the cover toward the 5-R lever side just before the cover contacts the case.
- Install the ten cover-to-case bolts, begining with the two alignment-type bolts, using a 10 mm socket and a torque wrench.
Torque: 14 N-m (10 lb-ft)
3. Offset lever, detent ball and spring
2. Extension housing assembly
- Apply a 3 mm (1/8 in.) bead of RTV sealant to the sealing surface of the extension housing.
- Lubricate the detent/guide plate in the extension housing with lithium grease. Install the detent ball in the "3-4" position of the detent pattern of the plate.
- Place the offset lever (with detent spring) in the extension housing detent/guide plate area and push the extension against the case and shift cover.
- Guide the offset lever onto the shift shaft as you push the extension housing. You will have to compress the detent spring against its ball to fit the parts easily.
- Apply sealer to the threads of the top two extension housing-to-case bolts and install them. Install the other six bolts as well. Tighten the bolts, using a 15 mm socket and a torque wrench.
Torque: 30 N-m (23 lb-ft)
- Apply sealer to the threads of the back-up lamp switch and the drain plug and install them, using suitable wrenches.
1. Offset lever roll pin
- Install the offset lever-to-shift shaft roll pin, using a hammer.
12. Input shaft bearing retainer, bearing outer race and shim(s)
SHIM ADJUSTMENT (INPUT/MAINSHAFT END PLAY)
- Turn the transmission case on end, and mount a dial indicator on the extension housing. Set up the indicator to measure input/mainshaft end play. Move the input/mainshaft up and down and read the total amount of indicator travel.
- Select a shim which is the same thickness as the indicator reading (± 0.001 inch).
This will give an end play of zero. Application and ID
- Remove the input bearing retainer.
- Install the selected shim(s) behind the input bearing outer race in the retainer. If two shims are used, put the thinner one in first.
- Install the retainer against the case.
Torque: 20 N-m (15 lb-ft)
- Re-check the input/mainshaft end play.
Change the shim again if end play is not zero (± 0.001 inch).
- Apply a 1/8 inch (3 mm) bead of RTV sealant on the sealing surface of the retainer.
- Apply sealer to the threads of the four retainer bolts.
- Install the retainer against the case.
Torque: 20 N-m (15 lb-ft)
- Install the speedometer driven gear assembly.
- Remove the transmission from the holding fixture.
- Loosen the fill plug and fill with Dexron(R) II Automatic Transmission Fluid.
- Install the clutch housing to the case.
Torque: 76 N-m (56 lb-ft)
- Install the clutch release bearing and shift fork.
- Clean the sealing surface of the shift control lever and inspect it for warpage.