Ask our Experts

Iffy indicators and nut lubrication.

Q

My daughter’s 1985 Renault Trafic camper van has a persistent whine coming from its transmission. We took it to a local gearbox firm who fitted a replacement crownwheel and pinion – but the whine remains. What can you suggest? David Morris, Somerset

A

Whining may have more than one cause. Try to get your head around all the possible souces of the noise, then rule them out until your find the culprit – or culprits.

It’s important to stress that whining that slowly asserts itself over a period of time is not a sign of imminent collapse. A sudden onset of noise might be a harbinger of doom – but first check the oil level isn’t critically low due to a failed seal or a missing casing bolt.

Test-drive the van and listen carefully to the types of noise produced and when they occur. A moaning, grinding or whining noise that’s present all the time might be down to worn gearbox bearings. Gnashing sounds tend to be caused by gear teeth that are worn or not meshing correctly – or perhaps by a bearing in the terminal stages of wear. Incorrect meshing can be caused by a collapsing bearing or a broken bell-washer (a sprung concave washer that keeps everything in place on a shaft). The gnashing may briefly abate when the throttle’s released, then resume as the drivetrain goes into overrun. This is sometimes accompanied by a tendency to stick in or jump out of gear.

Noises that come from the final drive may be due to worn or slack bearings, or due to incorrect adjustment of its crownwheel and pinion. Grinding or rumbling noises suggest rough bearings. Howling or moaning when accelerating or decelerating point to poor adjustment.

Heavy vibration in the instant of switching between acceleration and deceleration is often caused by insufficiently preloaded pinion shaft taper-roller bearings. This can be cured by tightening the nut on the end of the shaft or adjusting the shimming. A whine or gnash that’s only obvious when coasting in neutral or when dipping the clutch may be down to overtightened pinion bearings.

Clonking between acceleration and overrun points to too much backlash between the crownwheel and pinion, cured by adjusting the position of the crownwheel bearings. First, check for excessive play in propshaft or driveshaft joints and worn hub spines.

Grinding that occurs when accelerating hard with the steering on full lock may indicate wear of the sun and planet gears in the differential.

The crownwheel and pinion are generally not prone to wear. Perhaps those of your Renault were maladjusted to begin with, either due to a previous overhaul or worn bearings throwing the gears out of their correct mesh? The new gear set might have been installed with the same incorrect adjustment as before – or simply been adjusted badly.

Hopefully, we’ve given you enough clues to decide whether the final drive is really to blame. In any event, it may be most cost-effective to replace the whole ‘box. You might be able to source one from another motorhome that’s covered a low mileage.