Pinion Bearing Failures |
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Pinion Bearing Failures |
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| Everything you wanted to know and were afraid to ask: | ||
| What is a pinion bearing: the 968 has a transaxsle i.e. the gearbox, final drive and differential all in one unit. The gearbox output shaft has at its end a pinion gear driving the crown wheel. This shaft has a big 'pinion' bearing on one end and a smaller one at the other end. A pre-load is applied by way of shims and a nut at the smaller end of the shaft. |
| Symptoms: Road speed related whine audible from 35-40 mph. Test on straight road with smooth surface for minimum tyre noise. Close roof and windows, accelerate to 80-85 mph, lift off, if you hear noise resembling a jet plane slowing down on a runway - you have a problem ! Alternatively you can secure the rear of the car on stands, run the car in top gear and listen to the noise from the gearbox. If you haven't got LSD you can stop one or the other wheel to eliminate possible wheel bearing and CV joint noise. |
| Cause: Too much pre-load on the pinion bearing at assembly. Getrag ( who made these transmissions for Porsche ) uses a computer controlled robot, which has not always been accurate. |
| Repair: This
requires complete dismantling of the transmission.
Porsche allows 15 hours, but everyone says it is not
enough. One London, UK, dealer quoted 40 hours at £70
plus tax = £3290 = over $5000 just for labour. Parts are
not too expensive, but it may be wise to replace all the
bearings. Setting the correct free play - 'backlash'
while at the same time achieving the correct pre-load
requires an accurate measuring instrument, choice of
shims, patience and experience. Make sure your mechanic / shop have the necessary skills. |
| Prevention: Check for leaks, correct oil level. It may be a good idea to change the oil at 20,000 miles or maybe even more often. | ||
