Rear bearings excessive play - 310R

[ScottR400D]

They don't look too good after such a short time and mileage. Very odd. 

What is the discolouration?  From heat or is there something on the shaft? The splines also look quite worn and corroded for such a young car. How tight were the bearings on the shafts? 

I was thinking of changing to this new bearing but not so sure now! Is this the only example of an issue that we've seen? 

[Beagler]

Looks like caused by heat. What do the brake discs look like.

[David_Long]

For what it's worth, my thoughts are the pictures indicate a bearing failure rather than a driveshaft problem. It could be through ingress of water as the corrosion on the splines and threads is not what you'd expect on a Caterham of this age. The staining could be overheating, or it could be rust, or even a bit of both - it needs closer examination to be sure.  I would suggest it has had a history of being run under torqued at some stage that this has stressed/worn the bearings an allowed seepage of moisture (water from rain or washing) to ingress the splines around the driveshaft and bearing. 

Edit to add there is some evidence in the picture to suggest polishing of the bearing which may indicate movement (under torqued).

[ChrisC]

From my personal experience I am not expecting the driveshaft / bearing to be reusable if I need to dismantle them.  My Oct 2019 kit (2020 registered) has been through two driveshafts and rear bearings sets.  Fretting caused damage to the inner race, and the driveshaft surface.  Both sides showed the same damage, and it was worse over time / distance travelled.  My driveshaft where replaced at different times so I it was possible to observe.  I now recommend SKF anti fretting paste during assembly, which I applied to one of the driveshafts, only time will tell if it saves the driveshaft / bearing.

 

[JonPivo]

Brake discs are fine. 

[7 wonders of the world]

what does the inner bearing feel like when rotated by hand - any noticeable variation inner to outer...?

any signs of discolouration on the inner race of the inner bearing, there appears no signs fretting on the shaft just a light polished witness

did you check the torque prior to stripping down..?

 

[Beagler]

The source of heat seems to be the driveshaft hub where the u/j is and has been very hot and most discoloured. Would be interested to see the joint when the shaft is removed and  the gaiter. The bearing seat is the lightest so maybe the bearing was a casualty of the heat source.

[aerobod - near CYYC]

One thing I would check is that the driveshaft mounting surface for the bearing is either shorter then the thickness of the inner race or that the hub has enough relief on it such that the hub does actually clamp the bearing instead of either the nut bottoming on the thread or the hub bottoming on the bearing mounting surface.

The discolouration on the shaft looks more like lubricant varnish due to the bearing spinning, as opposed to the steel heating up enough to get into the heat treatment range. In the slight possibility the discolouration is due to oxidation in the heat treatment range, the shaft and hub likely would need replacement due to change in the steel properties.