Unfortunately, there's no single answer without knowing this. The information is usually found on a tag on the transmission itself, your owner's manual (if you have it), or a parts lookup using your VIN number at a parts store or online.
However, common gear oils used in manual transmissions of that era are:
* 75W-90: This is a very common and likely correct choice for many 86 Ranger manual transmissions. It's a good general-purpose gear oil.
* 80W-90: Similar to 75W-90, but slightly thicker. This might be specified if you're experiencing some gear whine or noise.
Important Considerations:
* API Service Classification: Look for an API (American Petroleum Institute) classification on the gear oil bottle. GL-3, GL-4, and GL-5 are common classifications for manual transmissions. GL-5 is generally suitable for hypoid gears (found in some rear axles, but less common in manual transmissions in that era). GL-3 or GL-4 are more likely to be the correct choice for your transmission. Your owner's manual will have this info if you can find it.
* Synthetic vs. Conventional: Synthetic gear oils are generally better in terms of performance and longevity, but they are more expensive. Conventional gear oil is perfectly acceptable for many applications.
Do not guess! Using the wrong gear oil can damage your transmission. Identify your transmission type and consult a repair manual, parts store, or online resources using your VIN number to determine the correct gear oil specifications for your specific vehicle.
