Hi, I have installed a brand new T5-Z spec in my Plus 8 Morgan (240 hp). Everything was Ok and quiet for the first 75 miles. When I took it out the next time as soon as I put it in 5th gear and put it under load, this loud rattling noise came from the gearbox. The other four gears are quiet. The shifter also jerks back (1/8" at the top of the 6" lever) quite violently but a few seconds after the noise starts. The noise is a loud whirring and sounds like someone gargling. Oil level is correct and ATF. The box is out of the car and all looks ok inside. Any suggestions as to the cause please?