1988 Chevrolet 1 Ton Trans Manual

The 1988 Chevrolet 1 Ton Trans Manual covers the 1-ton truck series with manual transmission options including the 4-speed and 5-speed manual transmissions. This manual provides comprehensive information on operation, maintenance, troubleshooting, and specifications for the THM400, SM465, and NV4500 manual transmissions used in 1988 Chevrolet 1-ton trucks (C30/K30 series). Below are key sections covering transmission identification, operation, maintenance procedures, and technical specifications.

1. Transmission Identification 2. Operation Guidelines 3. Maintenance Schedule 4. Technical Specifications 5. Controls and Operation 6. Fluid Requirements 7. Clutch System 8. Troubleshooting 9. Repair Procedures 10. Warranty Information 11. Service Contacts

Transmission Identification

Identify your transmission type by checking the identification tag on the transmission housing or referring to your vehicle's VIN code.

Transmission Code	Type	Gear Ratios
SM465	4-Speed Manual	6.55:1 (1st), 3.58:1 (2nd), 1.70:1 (3rd), 1.00:1 (4th)
NV4500	5-Speed Manual	6.34:1 (1st), 3.44:1 (2nd), 1.71:1 (3rd), 1.00:1 (4th), 0.73:1 (5th)
THM400	3-Speed Auto	2.48:1 (1st), 1.48:1 (2nd), 1.00:1 (3rd)
Location	Driver side transmission housing	Metal tag with model number
VIN Code	8th character indicates transmission	M=Manual, A=Automatic

Operation Guidelines

Proper shifting techniques and operational procedures for maximum transmission life.

Clutch operation: Fully depress clutch pedal before shifting gears.
Shifting sequence: Use progressive shifting (1-2-3-4-5) without skipping gears.
Load capacity: Do not exceed 10,000 lbs GVWR for C30 series.
Grade assistance: Use lower gears when descending steep grades.
Cold weather: Allow transmission fluid to warm up before heavy loading.

WARNING! Do not rest hand on shift lever while driving to prevent premature wear.

Maintenance Schedule

Regular maintenance intervals for optimal transmission performance.

Fluid change: Every 30,000 miles or 24 months
Clutch adjustment: Every 15,000 miles
Transmission mount inspection: Every 25,000 miles
Shift linkage lubrication: Every 10,000 miles
Complete overhaul: 100,000 miles or as needed

CAUTION! Use only recommended transmission fluids to avoid damage.

Technical Specifications

Transmission Types: SM465 4-speed, NV4500 5-speed manual
Case Material: Cast iron housing
Fluid Capacity: 4.5-5.5 quarts depending on model
Torque Capacity: Up to 460 lb-ft input torque
Shift Pattern: H-pattern with reverse left and up
Weight: 125-145 lbs depending on model
Input Shaft: 10-spline or 1-3/8" 10-spline
Output Shaft: 32-spline for heavy-duty applications

Controls and Operation

Understanding transmission controls and proper operating procedures.

Shift Lever: Floor-mounted with direct linkage to transmission.

Gear positions: 1st gear (granny low), 2nd, 3rd, 4th, Reverse (with lockout). Synchronizers: 2nd, 3rd, and 4th gears synchronized. Clutch: 11-inch diaphragm spring type, hydraulic operation. Shift quality: Firm, positive engagement with minimal play.

Fluid Requirements

Proper fluid types and capacities for each transmission model.

SM465: 80W-90 GL-4 gear oil (5 pints)
NV4500: 80W-90 GL-4 gear oil (5.5 pints)
Drain and fill: Remove fill plug, drain plug located on bottom
Inspection: Check for metal particles in drained fluid

Tip: Check fluid level with vehicle on level surface.

Clutch System

Clutch assembly specifications and maintenance procedures.

Clutch disc: 11-inch diameter, ceramic or organic material
Pressure plate: Diaphragm spring type, 1800 lbs clamp load
Release bearing: Graphite composition, pre-lubricated
Pedal free play: 1-1.5 inches at pedal pad
Hydraulic system: Master cylinder and slave cylinder service
Bleeding procedure: Bench bleed master cylinder before installation
Adjustment: Via pushrod at master cylinder

WARNING! Do not ride clutch pedal to prevent premature wear.

Troubleshooting

Common transmission problems and solutions.

Symptom	Possible Cause	Corrective Action
Hard shifting	Low fluid, worn synchronizers	Check fluid level, replace if contaminated
Gear grinding	Clutch not disengaging	Adjust clutch, check hydraulic system
Jumping out of gear	Worn detents, shift forks	Inspect shift mechanism, replace worn parts
Noise in neutral	Input shaft bearing	Replace input shaft bearing
Fluid leaks	Seals, gaskets, or case cracks	Identify source, replace seals/gaskets

Repair Procedures

Basic repair and replacement procedures for common issues.

Transmission removal: Support engine, remove driveshaft, disconnect linkages
Clutch replacement: Remove transmission, mark pressure plate orientation
Seal replacement: Input shaft and output shaft seal procedures
Bearing replacement: Press work required for main shaft bearings
Shift linkage: Adjust for proper gear engagement

CAUTION! Use proper lifting equipment when removing transmission.

Warranty Information

Original warranty coverage and terms for 1988 models.

Basic warranty: 12 months/12,000 miles. Powertrain coverage: 36 months/36,000 miles. Transmission specific: Covers defects in materials and workmanship. Service: Available at authorized Chevrolet dealerships. Claims: Required maintenance records must be provided.

Service Contacts

Technical support and service information resources.

Service Type	Contact Information	Hours
Technical Assistance	1-800-222-1020	Mon-Fri 8am-5pm EST
Parts Information	1-800-228-5872	Mon-Sat 8am-9pm EST
Customer Service	1-800-222-1020	Mon-Fri 8am-11pm EST
Online Resources	www.chevrolet.com	24/7 availability

Note: Have VIN ready when calling for technical assistance.