Why replace?
1. Seal failure or wear
Thread wear due to repeated disassembly and assembly: Bolts need to be removed every time the transmission oil is changed, and repeated operations may cause thread wear or deformation, resulting in poor sealing and oil leakage.
Washer aging: Some bolts come with disposable sealing washers (e.g., aluminum or rubber) that may collapse or lose elasticity after repeated use, and need to be replaced in one piece to restore sealing.

2. Corrosion or physical damage
Corrosion problem: In a humid, high-salt environment, bolts are prone to corrosion, resulting in difficult disassembly or reduced strength. For example, vehicles in coastal areas need to pay more attention to the condition of bolts.
Improper installation or external force damage: Excessive torque during installation may lead to slippage (such as oil leakage caused by untightened bolts), or accidental impact may lead to deformation and fracture of bolts.

3. Preventative maintenance
Recommendations for regular replacement: Some service manuals recommend replacing bolts and washers at specific mileage (e.g., every time the transmission oil is changed) to avoid sudden failures.
Avoid collateral losses: If the bolt fails and causes oil leakage, it may lead to insufficient lubrication, overheating or even damage to the gearbox, and the replacement cost is much lower than that of the repair gearbox.

4. Installation specifications and quality of accessories
The importance of standard installation: It is necessary to operate in strict accordance with the torque requirements of the maintenance manual, excessive force will lead to slippage, and insufficient torque may cause oil leakage.
Accessory compatibility: The use of non-genuine or inferior bolts can result in mismatched dimensions or materials, exacerbating sealing issues.

When do I need to replace it?
Signs of an oil spill: Oil stains around the oil pan.
Abnormalities such as thread damage, gasket collapse or corrosion are found during the inspection.