Ok, after a week or so of pacing up and down racking my brain to figure out the problem I'm no any closer.
I spoke to the guys down at Big Rigs WA this morning and the consensus is faulty servos.
Thank you all, and Lorrey in particular for his great help
I thought about it more on the drive home and did some more tests this afternoon to try and understand the problem.
if I swapped servo plugs and channels, and the problem was still there.. does that not rule out faulty servos?
Here's a 30 second clip (cut from 5 mins) of the machine running with the hydraulic motor on. Notice the engine noise get weaker and weaker..
http://www.facebook.com/photo.php?v=3775260663515
Anybody have any ideas before I take her into a hobby shop tomorrow?
P.s. sorry to lure you onto facebook... it was the easist way for me to upload the clip.