ford tsb about using mercon 5 on 4r100 transmission

Ford TSB: Why Using Mercon V in a 4R100 Transmission is Not Recommended

When it comes to maintaining your vehicle's transmission, it's essential to use the right fluid for optimal performance and longevity. In this article, we'll explore why using Mercon V in a 4R100 transmission is not recommended, as per Ford's Technical Service Bulletin (TSB).

Mercon V: A Slower-Acting Fluid

The main issue with using Mercon V in a 4R100 transmission is that it has a slower acting friction coefficient compared to Mercon ATF+4. This means that the T/C clutch and other friction elements may not have enough grip to handle the transmission's torque capacity. In fact, if you multiply the engine's peak torque by the T/C ratio, you'll get an idea of just how much grip is needed.

The 4R100 transmission has a torque capacity of 1,000 ft-lbs, which is significant. However, the transmission controls and clutches are designed to handle this level of torque, as they typically don't perform full-throttle upshifts into overdrive (OD) anyway.

FMC's Re-engineering Effort

Ford Motor Company (FMC) re-engineered their ATF fluid to make it less prone to oxidation and burning. While this improvement made the fluid slightly less grippy, it also reduced its ability to withstand high temperatures and extreme driving conditions.

The additives in Mercon V are designed to reduce friction, which can lead to 'shudder' or slipping under steady-state cruise conditions. This is not a problem unique to synthetic fluids, as even conventional fluids can exhibit similar behavior.

Why Not to Use Mercon V in a 4R100 Transmission

So, why should you avoid using Mercon V in a 4R100 transmission? The answer lies in the additives, which are designed for use in smaller transmissions like the 4R70W. These additives can cause problems in larger transmissions like the 4R100, which has a higher torque capacity and requires more grip to operate smoothly.

Ford's Testing Reveals Issues

According to Mark K, a Ford transmission engineer who used to post on the Transmission Discussion Forum (TDS), using Mercon V in a 4R100 transmission can lead to eventual failure. He claimed that this would occur after more than 10,000 miles of use, but it would happen nonetheless.

While some may disagree with Mark's assessment, his expertise and reputation in the field are undeniable. As he said, 'ignorance is bliss,' so if you're unsure about using Mercon V in your 4R100 transmission, it's best to err on the side of caution and stick with Mercon ATF+4.

In conclusion, using Mercon V in a 4R100 transmission is not recommended due to its slower acting friction coefficient and additives designed for smaller transmissions. Ford's testing has revealed issues with using this fluid in larger transmissions like the 4R100, which can lead to eventual failure. To ensure optimal performance and longevity of your transmission, it's essential to use the right fluid for your vehicle. Always consult your owner's manual or speak with a qualified mechanic if you're unsure about the best fluid to use in your vehicle.

Ford tsb about using mercon 5 on 4r100 transmission