XRAY - Model racing cars

I need some help, I recently purchased a T2 second hand. I believe the car was well maintained and well cared for. The person upgraded to a 007 kit. My problem is this, under power with the car on the track a clicking is heard. On the bench, on the stand the car sounds smooth. While going thru the car I found that two of the cvds are very smooth operating and the other 2 are not as smooth. I tried to rebuild them but if I put any pressure at all on the pin with the set screw the cvd binds. Any less pressure and the set screw will allow the pin to slide right out easily. I don't see any visable damage to the cvd parts and I tried using new pins, with no luck smoothing it out. Any suggestions other than replacing the cvd's?

Did you apply grease to the CVD couplings?

A thing which can help is to replace the following parts:

981210 Pin 2x10 (10)
305231 T2 Drive Shaft Coupling – Hudy Spring Steel™

And yes it's a good point to grease this after assembling.

Tony,
It doesn't appear that there is any greas on the two smoot operating ones. But yes I did apply grease to the one I rebuilt.

Joep,
I did replace the pin, I thought it may be bent which would cause binding. I did not have a spare coupler on hand though. I'll try that and see.

Thanks guys , anyone else?

It must be the cylinder that is catching since you say the pin drops through ok. Check whether the edges of the hole in the axle that the cylinder goes into are smooth. If they feel sharp lightly sand them down a bit with fine grain sanding paper.

Should you just use xray grease or thicker stuff? Should the grease go only on the coupler?

I use normally the grease for the diff's. I put some on de coupling and blow a little with compressed air over it and wipe the grease on the outside off. For me this works....

I apply a drop of the XRay grease on the cyclinder and spread it all around before inserting it. Works great for me.