1987 GMC S15 Manual Transmission Fluid
The 1987 GMC S15 features a manual transmission system requiring specific fluid types and maintenance procedures for optimal performance. Proper fluid selection, checking methods, and replacement intervals are crucial for transmission longevity and smooth shifting operation. Below are key sections covering fluid specifications, maintenance procedures, troubleshooting, and technical details.
Fluid Specifications
The 1987 GMC S15 manual transmission requires specific fluid types for proper lubrication and cooling of transmission components.
| Fluid Type | Specification |
|---|
| Manual Transmission Fluid | GM Part No. 12345349 or equivalent |
| Alternative Fluid | SAE 75W-85 GL-4 Gear Oil |
| Viscosity Grade | 75W-85 or 80W-90 |
| API Classification | GL-4 (Do not use GL-5) |
| Capacity Range | 3.5 - 4.2 quarts (varies by model) |
| Color | Amber when new, darkens with use |
| Smell | Distinct petroleum odor |
Checking Transmission Fluid
Regular fluid inspection ensures proper transmission operation and early problem detection.
- Park vehicle on level surface and engage parking brake.
- Run engine until transmission reaches operating temperature.
- Locate transmission fill plug on driver's side of transmission case.
- Clean area around fill plug before removal.
- Remove fill plug - fluid should be level with bottom of fill hole.
- If fluid is low, add recommended fluid until it begins to seep from fill hole.
- Reinstall fill plug and tighten to specification.
WARNING! Transmission fluid may be hot - wear protective gloves. Ensure vehicle is securely supported.
Fluid Replacement Procedure
Complete fluid replacement procedure for maintenance or contamination issues.
- Position vehicle on level surface and secure with wheel chocks.
- Place drain pan under transmission drain plug.
- Remove fill plug first, then drain plug to allow complete drainage.
- Allow fluid to drain completely (approximately 15-20 minutes).
- Clean drain plug and reinstall with new washer if required.
- Fill transmission through fill hole using pump or squeeze bottle.
- Continue filling until fluid reaches bottom of fill hole.
- Reinstall fill plug and tighten to 15-20 ft-lbs torque.
- Check for leaks and test drive vehicle.
CAUTION! Use only recommended fluid types. Overfilling can cause seal damage and leakage.
Recommended Fluid Types
- Primary Recommendation: GM Manual Transmission Fluid (Part No. 12345349)
- Alternative Option 1: SAE 75W-85 GL-4 Gear Oil
- Alternative Option 2: SAE 80W-90 GL-4 Gear Oil
- Premium Synthetic: Synthetic 75W-85 GL-4 (improved cold weather performance)
- Do Not Use: GL-5 gear oils (can damage synchronizers)
- Do Not Use: Automatic transmission fluid (ATF)
- Do Not Use: Engine oil or universal gear oils
Transmission Capacity
Transmission fluid capacity varies by specific transmission model and application.
| Transmission Model | Fluid Capacity | Drain Interval |
|---|
| Borg-Warner T5 | 3.5 quarts (3.3 liters) | 30,000 miles |
| Isuzu MSG | 4.2 quarts (4.0 liters) | 30,000 miles |
| New Process AY6 | 3.8 quarts (3.6 liters) | 30,000 miles |
| After complete rebuild | Add 0.5 quart extra | Initial 500 miles |
Maintenance Schedule
Regular maintenance ensures transmission longevity and optimal performance.
- Initial Inspection: Check fluid level every 1,000 miles for first 3,000 miles
- Regular Checks: Inspect fluid level every 3,000 miles or 3 months
- Complete Change: Replace fluid every 30,000 miles or 2 years
- Severe Service: Change fluid every 15,000 miles (towing, off-road use)
- Storage: Change fluid before extended storage periods
- After Repair: Always replace fluid after transmission service
Troubleshooting Common Issues
Identifying and resolving common manual transmission fluid-related problems.
| Symptom | Possible Cause | Corrective Action |
|---|
| Difficult shifting | Low fluid level or wrong fluid type | Check and correct fluid level/type |
| Grinding gears | Contaminated or degraded fluid | Drain and replace with fresh fluid |
| Transmission noise | Insufficient lubrication | Check fluid level and condition |
| Fluid leakage | Worn seals or overfilling | Inspect seals and correct fluid level |
| Hard cold shifts | Incorrect viscosity fluid | Use proper 75W-85 fluid |
| Burning smell | Overheating transmission | Check fluid level and driving habits |
Tools Required
Essential tools for proper transmission fluid maintenance.
- 3/8-inch drive ratchet with extensions
- 24mm socket for fill and drain plugs
- Fluid transfer pump or squeeze bottle
- Drain pan (minimum 5-quart capacity)
- Torque wrench (20-100 ft-lbs range)
- Safety glasses and chemical-resistant gloves
- Jack stands or vehicle lift
- Wheel chocks and shop towels
Safety Precautions
Critical safety measures when working with transmission fluid.
- Always work in well-ventilated area - transmission fluid fumes can be harmful.
- Wear safety glasses and gloves to prevent skin contact with fluid.
- Use jack stands - never work under vehicle supported only by jack.
- Allow transmission to cool before draining hot fluid.
- Clean spills immediately - transmission fluid is slippery and flammable.
- Dispose of used fluid properly at approved recycling facility.
- Keep fluid away from children and pets.
WARNING! Transmission fluid is petroleum-based and flammable. No smoking or open flames near work area.
Technical Specifications
Detailed technical specifications for 1987 GMC S15 manual transmission systems.
- Transmission Models: Borg-Warner T5, Isuzu MSG, New Process AY6
- Fluid Type: Manual Transmission Fluid GL-4
- Viscosity Range: SAE 75W-85 to 80W-90
- Operating Temperature: -40°F to 300°F (-40°C to 149°C)
- Fill Plug Torque: 15-20 ft-lbs (20-27 Nm)
- Drain Plug Torque: 15-20 ft-lbs (20-27 Nm)
- Fluid Change Interval: 30,000 miles or 2 years
- Warranty Coverage: See separate warranty section
Warranty Information
Manufacturer warranty details and coverage limitations.
GMC provides limited warranty coverage for transmission components. Fluid-related failures are typically covered only if caused by manufacturing defects and proper maintenance procedures were followed. Keep records of all fluid changes and maintenance. Warranty does not cover damage from using incorrect fluid types, neglect, or improper maintenance. For warranty claims, contact authorized GMC dealership with maintenance records.
Customer Support: Contact GMC Customer Service at 1-800-GMC-8782 or visit www.gmc.com
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