1987 GMC S15 Manual Transmission Fluid

The 1987 GMC S15 features a manual transmission system that requires specific fluid types and maintenance procedures for optimal performance. Proper transmission fluid selection, checking procedures, and replacement intervals are essential for maintaining smooth shifting, preventing wear, and ensuring longevity of the transmission components. Below are key sections covering fluid specifications, maintenance procedures, troubleshooting, and technical details.

1. Transmission Fluid Specifications 2. Fluid Capacity and Types 3. Checking Transmission Fluid Level 4. Fluid Replacement Procedure 5. Recommended Maintenance Schedule 6. Compatible Fluid Brands 7. Transmission Specifications 8. Common Transmission Issues 9. Tools and Equipment Needed 10. Safety Precautions 11. Troubleshooting Guide

Transmission Fluid Specifications

The 1987 GMC S15 manual transmission requires specific fluid types to ensure proper lubrication and performance.

Specification	Details
Primary Fluid Type	GM Manual Transmission Fluid (GM P/N 12345349)
Alternative Options	SAE 80W-90 GL-4 Gear Oil
Viscosity Grade	80W-90
API Classification	GL-4
Special Notes	Do not use GL-5 gear oil as it may damage synchronizers

Fluid Capacity and Types

Understanding the correct fluid capacity is crucial for proper transmission maintenance.

Total Capacity: 3.5 quarts (3.3 liters)
Drain and Refill: 2.8 quarts (2.6 liters)
Fluid Type: Manual Transmission Fluid 80W-90 GL-4
Approved Brands: GM, AC Delco, Mobil, Castrol

IMPORTANT! Using incorrect fluid types can cause synchronizer damage and shifting problems.

Checking Transmission Fluid Level

Regular fluid level checks help prevent transmission damage and ensure smooth operation.

Park vehicle on level surface and engage parking brake
Clean area around fill plug on transmission side
Remove fill plug (3/8-inch square drive)
Fluid should be level with bottom of fill hole
If low, add fluid until it begins to run out fill hole
Reinstall fill plug and tighten securely

CAUTION! Check fluid when transmission is at operating temperature for accurate reading.

Fluid Replacement Procedure

Complete fluid replacement procedure for optimal transmission performance.

Drive vehicle to warm transmission fluid
Park on level surface and engage parking brake
Place drain pan under transmission
Remove drain plug (bottom of transmission case)
Allow fluid to drain completely
Clean drain plug and reinstall
Remove fill plug and add new fluid until it runs out
Reinstall fill plug and tighten both plugs securely

WARNING! Transmission fluid may be hot - wear protective gloves and eyewear.

Recommended Maintenance Schedule

Follow this maintenance schedule for optimal transmission longevity.

Service Interval	Maintenance Task
Every 30,000 miles	Check fluid level and condition
Every 60,000 miles	Complete fluid replacement
Every 100,000 miles	Inspect transmission mounts and linkages
As needed	Check for leaks and unusual noises

Compatible Fluid Brands

Recommended transmission fluid brands for the 1987 GMC S15.

GM Original Equipment: GM Manual Transmission Fluid
AC Delco: 10-4004 Manual Transmission Fluid
Mobil: Mobilube 1 SHC 75W-90
Castrol: Castrol Syntrans Transaxle 75W-90
Valvoline: Valvoline High Performance Gear Oil 80W-90

NOTE: Always verify GL-4 specification before purchase.

Transmission Specifications

Technical specifications for the 1987 GMC S15 manual transmission.

Transmission Model: Borg-Warner T-5
Gear Ratios: 1st: 3.76, 2nd: 2.18, 3rd: 1.44, 4th: 1.00, 5th: 0.86
Case Material: Aluminum
Shift Pattern: 5-speed with reverse
Weight: Approximately 75 lbs (34 kg)
Lubrication System: Splash lubrication

Common Transmission Issues

Frequent problems associated with manual transmission fluid and maintenance.

Issue	Possible Cause	Solution
Hard shifting	Old/wrong fluid, low level	Replace with correct GL-4 fluid
Grinding noises	Worn synchronizers, wrong fluid	Use proper GL-4 fluid, inspect synchros
Fluid leaks	Worn seals, loose plugs	Replace seals, tighten plugs
Transmission overheating	Low fluid, heavy towing	Maintain proper fluid level

Tools and Equipment Needed

Essential tools for transmission fluid maintenance.

3/8-inch square drive ratchet
Drain pan (minimum 4-quart capacity)
Fluid transfer pump
Torque wrench
Safety glasses and gloves
Shop towels and cleaner
Jack stands (if elevated access needed)

SAFETY FIRST! Always use jack stands when working under vehicle.

Safety Precautions

Important safety measures when working with transmission fluid.

Wear protective gloves and eyewear
Work in well-ventilated area
Use jack stands - never rely on jack alone
Allow transmission to cool before draining
Dispose of used fluid properly at recycling center
Clean spills immediately to prevent slips

WARNING! Transmission fluid is slippery and can cause falls if spilled.

Troubleshooting Guide

Common transmission problems and solutions.

Symptom	Possible Cause	Corrective Action
Difficulty shifting into gear	Low fluid, wrong fluid type	Check level, replace with GL-4 fluid
Transmission noise in neutral	Low fluid level	Add fluid to proper level
Gear popping out	Worn shift linkage, low fluid	Inspect linkage, check fluid
Fluid discoloration	Contamination, overheating	Complete fluid replacement
Leaking from fill plug	Loose plug, damaged threads	Tighten plug, repair threads

Professional Service: Contact certified mechanic for complex transmission issues.

Technical Support: GM Customer Service 1-800-462-8782