Transfer Case - Overhaul - New Venture 233 GMC Typhoon I

IDENTIFICATION

Transfer case can be identified by an I.D. tag, located on rear case. (Scheme 13) I.D. tag provides model number, assembly number and low range ratio. This information is necessary when ordering parts.

Scheme 13

DESCRIPTION

Model 233 transfer case is a chain drive, 2-piece aluminum case, 3-position unit. Transfer case uses an electronic control system and a shift motor to shift the transfer case.

GEARSHIFT LINKAGE

Model 233 uses a electronic control system and shift motor for transfer case shifting and is not equipped with transfer case gearshift linkage.

Removal

Mark front drive shaft and flange for alignment purposes. Remove front drive shaft. Remove flange. Discard washer and nut. Using a screwdriver, carefully remove oil seal. Ensure seal contact surface is clean.

Installation

Apply ATF to seal lip and yoke seal surface. Install oil seal and yoke with NEW washer and nut. Install front drive shaft using alignment marks. Check transfer case fluid.

Mark rear drive shaft and flange for installation purposes. Remove rear drive shaft. Tap extension housing clockwise and remove extension housing. DO NOT pry on extension housing. Using a screwdriver, remove oil seal from extension housing.

Using bushing driver, replace bushing in extension housing. Install NEW extension housing oil seal. Apply silicone sealant to extension housing mating surface. Install extension housing. To complete installation, reverse removal procedure.

ELECTRONIC SYSTEM

To test electronic system and components on all models except 1991-92, see TRANSFER CASE - ELECTRONIC DIAGNOSIS article. On 1991-92 models testing is not available.

Scheme 14

Will Not Shift Or Difficult To Shift

Vehicle operated too long on dry paved surface. Stop vehicle. Place transmission in Reverse or Neutral to relieve drive line torque. Ensure correct fluid is used. Internal parts may be worn or damaged.

Noisy In All Gears

Check fluid level. Ensure correct fluid is used. If fluid is okay, locate possible internal mechanical problem.

Jumps Out Of Gear Or Noisy In 4WD

Transfer case internal shift mechanism faulty. Range fork damaged. Fork pads are worn. Shift fork binding. Low range gear worn.

Fluid Leaking From Vent Or Seals

Transfer case overfilled. Vent plugged. Output shaft seals are damaged or not installed properly.

1. Shift transfer case into 4H and disconnect battery negative cable. Raise vehicle, remove skid plate and drain fluid.
2. Mark front and rear output shaft yokes to drive shafts for reassembly reference. Support transfer case and remove rear crossmember. Remove drive shafts.
3. Disconnect speedometer cable, electrical connections and vacuum (hoses) harness at transfer case. Remove transfer case attaching bolts. Remove transfer case from vehicle.

1. Clean all old gasket material from transmission and transfer case mating surfaces. Position NEW gasket on transfer case with orientation tab at upper left bolt hole.
2. Install transfer case, aligning splines of input shaft with transmission. Slide transfer case forward until seated against transmission. Install transfer case attaching bolts and tighten to specification. See «TORQUE SPECIFICATIONS»(/gmc/typhoon/i-1991-1993/remont/transfer-case/#transfer-case-overhaul-new-venture-233__torque-specifications) . Install rear crossmember.
3. Attach speedometer cable, electrical connections and vacuum harness at transfer case. Using reference marks made during removal, reinstall front and rear drive shafts. Refill transfer case. Install skid plate and lower vehicle. Connect negative battery cable. Road test vehicle.

TRANSFER CASE DISASSEMBLY

Note. (Scheme 14)for exploded view of transfer case.

1. Remove front output yoke. Discard lock nut. Remove encoder motor, vacuum switch and speed sensor. Remove extension housing and rear output bearing retainer snap ring. Using 2 screwdrivers under each tab, remove pump retainer housing. Remove speedometer tone wheel from mainshaft. Remove rear case and oil pump as an assembly.
2. Remove pump pick-up screen and tube from rear case. (Scheme 15) Remove oil pump. Remove "O" ring from oil pump and discard. Mar k pump housing position for reassembly purposes. Separate oil pump halves. Note gear positions for reassembly reference and remove them from housing.
3. Remove mode shift fork spring. Using a soft hammer, tap front output shaft upward and remove with drive chain as an assembly. Remove mainshaft, mode fork and shift rail as an assembly. Remove mode fork and shift rail from synchronizer sleeve.
4. Mark synchronizer sleeve position for reassembly purposes. Remove synchronizer sleeve from mainshaft. Remove synchronizer hub snap ring. Remove synchronizer hub, synchronizer ring and drive sprocket. Slide range fork pin out of shift sector.
5. Remove range shift fork and range shift hub as an assembly. Remove shift sector, bushing and "O" ring. Remove shift detent pin, spring and plug. Remove front bearing retainer. Remove input gear snap ring.
6. Press input gear and planetary carrier assembly from annulus gear. Remove planetary carrier snap ring. Remove input gear snap ring, thrust washers and input gear from planetary carrier.
7. Remove all oil seals. Remove magnet from front case. Remove front bearing snap ring. Using a plastic hammer, remove front bearing. Press input gear bearing from front case.
8. Using slide hammer and internal puller, remove input gear pilot bearing. Press bearings from drive sprocket. Using internal puller and slide hammer, remove output shaft rear bearing.

Scheme 15

CLEANING & INSPECTION

Clean all parts with solvent. Dry all parts with compressed air, except bearings. Bearings must be wiped dry or allowed to air dry. Replace all oil seals, "O" rings and snap rings. Check all parts for wear or damage. Replace all worn or damaged parts. If annulus gear, inside front case, is damaged or worn, front case and gear must be replaced as an assembly. Replace oil pump as an assembly if any part is damaged or worn.

TRANSFER CASE REASSEMBLY

Note. (Scheme 14)for exploded view of transfer case. When installing bearings, ensure bearing bores are aligned with oil feed holes.

1. Lubricate all parts with Dexron-II ATF before installation. Install output shaft front bearing with NEW snap ring. Install output shaft oil seal in front case. Install snap ring on NEW input gear bearing.
2. Press input gear bearing so snap ring is seated against case. Using press, install NEW input gear pilot bearing. Assemble planetary carrier, input gear, thrust washers and lock ring.
3. Install snap ring. Ensure snap ring is seated in annulus gear groove. Start input gear shaft into bearing in front case. Press input shaft gear into bearing. CAUTION: DO NOT press against end surfaces of gear. Failure to use proper size tool could lead to gear case or thrust washer damage.
4. Install input gear snap ring. Install oil seal in front bearing retainer. Apply a 1/8" bead of silicone sealant to retainer mating surface and install on case. Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/typhoon/i-1991-1993/remont/transfer-case/#transfer-case-overhaul-new-venture-233__torque-specifications).
5. Install sector shaft "O" ring and bushing. Install range sector in case. Install detent, detent spring and plug. Tighten to specification. Install NEW pads and fork rail bushings on range fork. Install range fork and shift hub.
6. Ensure range fork pin is engaged with range sector slot. Press bearings into drive sprocket until bearings are flush with bore edge.
7. Install inserts and spring in synchronizer hub. Install sprocket on mainshaft. Install synchronizer ring on mainshaft. Ensure synchronizer ring is seated. Install synchronizer hub on mainshaft. Align and seat hub inserts on synchronizer ring lugs. Install synchronizer hub snap ring.
8. Install synchronizer sleeve on hub. (Scheme 16) Ensure sleeve is positioned so beveled spline ends are facing synchronizer ring. Install NEW pads on mode fork. Engage mode fork in synchronizer sleeve. Install mainshaft and fork assembly in case. Ensure mode fork shift rail is seated in both range fork bushings.
9. Install output shaft and drive chain assembly. (Scheme 17) Install mode shift fork spring on shift rail. Using bearing driver, install output shaft rear bearing. Lubricate bearing after installation. Install seal in oil pump feed housing. Assemble oil pump and install in housing. Tighten to specification.
10. Install oil pick-up tube "O" ring in oil pump. Install oil pump and pick-up tube in case. Ensure screen is properly positioned. (Scheme 15) Install magnet in front case. Apply 1/8" bead of silicone sealer to front case.
11. Install rear case and tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/gmc/typhoon/i-1991-1993/remont/transfer-case/#transfer-case-overhaul-new-venture-233__torque-specifications). Ensure mainshaft splines are engaged with oil pump inner gear and a washer is used on bolts at dowel locations. Install rear bearings in retainer. Apply 1/8" bead of silicone sealer and install retainer to case. Install rear retainer snap ring.
12. Install oil seal in extension housing. Install extension housing. Install encoder motor, vacuum switch and speed sensor. Install front companion yoke. Install NEW gasket on vacuum switch. Install vacuum switch in case. Fill transfer case with Dexron-II ATF.

Scheme 16

Scheme 17

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• TORQUE SPECIFICATIONS