BMW M4 2014-2020 Drivetrain Bolt Torque Specifications

Correct torque ensures proper clamping force, preventing bolts from loosening due to vibration and stress. Over-tightening can damage threads, cause bolt failure, or distort components like the transmission housing or differential. Under-tightening can lead to premature wear, component failure, and potentially dangerous situations, especially under high load conditions common with the M4.

Overtightening can stretch or break the bolt, damage the threads in the component (like the differential or driveshaft), and possibly cause pre-mature component failure. Undertightening can cause the bolts to loosen over time, leading to excessive play, vibration, noise, and potentially catastrophic failure of the drivetrain components. Examples include a loosened driveshaft causing severe vibration or a differential mount that could cause the differential to shift from its intended position.

It is highly recommended to use new, torque-to-yield (TTY) bolts for specific components such as the driveshaft and differential mounting. These bolts are designed to stretch upon tightening and cannot be reused safely. They provide a precise clamping load and are designed for one-time use. Reusing TTY bolts can result in unpredictable torque and may cause a failure. For standard bolts, while reusing is acceptable if they appear undamaged, consider replacement when working with critical components for optimal safety and performance.

Yes, but with discretion. For bolts that are particularly prone to loosening due to vibrations (such as driveshaft bolts or exhaust mount bolts in close proximity to drivetrain parts), using a thread locker like Loctite is often recommended. Refer to the specific repair manual for guidance, as some bolts do not require or recommend thread locker. Always ensure the use of the correct grade and type of thread locker as well.

Regular inspection of drivetrain bolts is beneficial, especially after work is performed on this system, hard driving or track use. A good practice is to check torque values every 10,000-20,000 miles, or more frequently if you experience drivetrain related symptoms such as vibrations, unusual noises or movement. Track or race use may require more frequent checks, sometimes as often as prior to every track event. It is crucial to recheck the bolts, even after using thread locker, after a brief period of normal driving to assure adequate clamp load and torque values.