Gearbox whining in 5th and 6th gear in Renault Trafic

A growing whine in higher gears in Renault Trafic and Master with PF6/PK6 gearboxes is a sign of worn shaft bearings. The bearing rollers wear until the cage no longer holds them and they move out of position. This causes a characteristic hum above 60 km/h that turns into a clear whine in 6th gear. The most common cause is neglected gearbox oil, ideally the original Elf Tranself. In PF6/PK6 gearboxes, oil should be changed about every 100,000 km even though the manufacturer gives no fixed interval. The level is filled until it overflows, not to the mark on the dipstick. Ignored whine ends with pitted races, damaged output shafts and differential, and then the only option is gearbox rebuild or replacement.

What should be replaced in a PF6/PK6 gearbox?

If caught early, the repair is relatively cheap: replace the full bearing set, eight pieces, preferably tapered bearings in OE specification, driveshaft and shaft seals, because leaks lower the oil level and bearings run dry, plus the plastic slide and oil feed channel, which almost always crack during dismantling. During assembly, correct tapered bearing preload and sealing the casing with silicone are critical. If gear changes are also rubbery or gears pop out, selector regeneration is usually added on these gearboxes.