XRAY - Model racing cars

Hi all,
I've been keeping an eye on a strange wear pattern in both the rear outdrives of our 1 year old t1r. Both the drive slots on the drive take up side have started to elongate, allowing the driveshaft plastic blades to have a fair amount of slack in the drive line. I realise i'm asking a lot expecting a regularly raced car component to last this long, and i've already ordered replacements. The reason that i have posted this is for 2 reasons i am curious, firstly the front diff is the same age and does not show this type of wear. Secondly, I would like to know if I have a larger problem looming up so that I do'nt destroy the new ones.
Any help appreciated
Phil.

Phil,

Did you change the plastic blades regularly, or are the original ones still in there?

is your rear diff tighter than the front? if so then that also may contribute towards the problem (and you hardly ever run a rear diff tighter than the front )

Remeber that when the car takes off the rear sinks down and will take more load on the drivetrain.

Tony,
they were the original blades, but i've just compared them against a new set and there is .002mm difference, and no sign of noticable side damage in the area of the wear mark. I have fitted new ones now, but the front blades are also the same age and dont give a problem. The rear diff is looser than the front, I think trickpatrick may have a point, the only thing is 4 of our friends all bought xrays at about the same time as us, and they dont seem to have the problem. Just being cautious really, i'm probably worrying over nothing but it just looks such an odd wear pattern.
Thanks for your help guys
Phil

The car is completely stripped every week - right back to chassis, bearings are cleaned and re-lubed every stripdown. Diffs are stripped completed every four meetings or twenty runs. The wear pattern has only started to show itself over the last four weeks. All driveshafts have been stripped and rebuilt, and are very smooth in action. All rear hub bearings were first stripped and lubed, but as the wear still persisted, they were then renewed. The wear pattern just kept on eating away steadily!. Layshaft bearings are free, and the rear and front suspension all fall free under their own weight with no shock attached, so I don't think its a binding issue.
The car is raced in 27t stock series. Is it worth replacing the bearings in the centre of the diff? - they have been lubed/cleaned and appear very free, don't really know what else to do. I suppose its possible I could have a pair of outdrives that have a slightly lower quality metal, but I find that almost impossible to believe after nearly a year of racing.
Perhaps i've got a gremlin from the twilight zone in there!!
Thanks for all your input anyway.
Phil