Why use a flush fluid?
As drain intervals increase, the likelihood of sludge and wear particles building up in the gearbox increases. Also, some lubricants have inherent sludging problems. Without flushing the gearbox, the sludge and wear particles will stay in the gearbox and contaminate the new oil that is introduced during an oil change. If you leave these contaminants in the gearbox, they can quickly cause damage to gears and bearings and cause the gearbox to fail.
