Grinding under load?

[Bman]

So. This weekend, I replaced my chain, cassette, rear gear cable (inner) and rear derailleur. The job went well, everything fit into place and the gears indexed nicely. I actually opted for a 9 speed Derailleur as there were no 8 speeds I could find. I was advised on here that this would be fine. Everything else is 8 speed (cassette and chain)

However, I am getting a strange grinding noise whenever the drive train is under reasonable load.

This griding only occurs when in the small chain ring. It doesnt happen in the large chainring.
It occurs if i am seated, or standing.
it only occurs under reasonable load. I cannot reproduce it with the wheel allowed to spin freely (or even with the wheel in the air and the brakes applied gently)

The noise seems to be coming from the back, possibly the bottom jockey wheel of the derailleur but i cant be sure as the conditions i need to replcate the noise prevents me taking a good look while it is happening.

I took it into the LBS for a 2nd opinion. The mechanic confirmed everything was fit correctly and he couldnt figure it out either. However his opinion was that it was coming more from the front (Bottom bracket/pedals) than the rear.

I might put the old derailleur back on tonight to see if that eliminates it.

Meanwhile, any ideas?

 

[Bman]

I think i have found the culprit

 

[gbb]

If there's no slipping, let the chain bed in and it will almost certainly stop making that noise after some miles..Happened on two of my bikes where ive only changed the chain. Its just the slight mis mesh of the components, they willsort themselves out.