Bearing no problems

David Hirst gets into gear a knotty problem with its cogs

Published:  15 August, 2012

When a 2004 ex-driving school Volkswagen Polo arrived at my workshop recently with gearbox problems it came as little surprise. However, further inspection revealed the fault turned out to be nothing to do with years of abuse by learner drivers.

In this case, the vehicle had the 02T transmission which is commonly fitted to a number of popular models across the VAG range. The symptoms of the fault were difficulty in engaging the gear together with a harsh grinding noise whilst in neutral when the engine was running.

The first step of my investigation in all cases like this was to drain and inspect the transmission oil, on doing so it became apparent that there was little of the recommended 2.1 litres remaining in the transmission. Closer examination of the oil in the drain tray revealed a small amount of metal debris.

There was now little option but to remove the transmission from the vehicle to inspect it internally.  I began by unbolting the driveshafts from the drive flanges on the transmission. When doing this I discovered the nearside drive flange was insecure and the centre bolt which attaches it to the differential had come undone, allowing the flange to lose contact with the housing oil seal and the transmission oil to escape.

Once the transmission was removed and on the bench, I began by removing the bolts retaining the gearbox end housing cover, followed by the housing cover and cover sealing gasket. Taking this cover off exposes the fifth gear assembly and I could immediately see the problem.

Needle roller

As you can see from the picture on p27, the fifth gear needle roller bearing had melted and broken up. Obviously, there are no circumstances where this would do a gearbox any favours but in this case, it was preventing the synchro-hub from freewheeling on the input shaft, effectively making fifth gear engaged all of the time.

Renewal of the fifth gear needle roller bearing on the 02T transmission is fairly straightforward. You first withdraw the fulcrum pin which retains the fifth gear selector fork and lift the selector fork away from the synchro-hub assembly. Remove the circlip retaining the fifth gear synchro-hub and slide the assembly from the input shaft complete with needle roller bearing and if necessary, remove the circlip from the fifth gear wheel and withdraw the wheel from the output shaft. The fifth gear bearing inner track can now be removed from the input shaft using a suitable puller.

Reassembly

To put it back together, I fitted the fifth gear wheel to the output shaft using a new retaining circlip. It should be noted that these circlips come in three different thicknesses and you should use the thickest possible so that it just fits. To install the new fifth gear needle roller bearing, begin by fitting the bearing inner track to the input shaft using a press and to avoid damage to the track a suitable size press piece, in this case, I used special tool VW 422. I then lightly oiled the new bearing and slide over the inner track, then fitted the synchro-hub assembly using a new circlip - again using the thickest one I had.

The next step was to fit the fifth gear selector fork together with the fulcrum pin, followed by the gearbox housing cover and a new sealing gasket. I then filled the transmission with the correct grade and quantity of oil.

The fifth gear wheel, synchro-hub and needle roller bearing on the 02T transmission can be renewed without removing the transmission from the vehicle although, in our case it was necessary to completely dismantle the transmission to check for any further damage due to it being driven with a low level of oil.

Now back on the road, this particular car should have years of life left in it. Due to the age of the car, had I quoted for an entirely new gearbox it would have sent it to the scrapyard for sure. However, for the price of some new bearings and consumables plus some of my time and know-how, the car is going to stay on the road for a while yet.

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