It is normal for a small amount of fork movement due to endplay in the crankshaft thrust washers and uneven pressure plate diaphram fingers.
If you have excessive fork shaking, besides the noise, if the clutch is still grabbing get in it and drive it 
To test your clutch strength, I take off in first gear and slightly overrev the engine before I push in the clutch pedal to shift into third gear. By missing 2nd gear and reving the engine up a little before releasing the clutch pedal quicker than normal, it is possible to test the bite of the clutch assm.
If the engine quickly slows down to the speed of the truck, your clutch still has some good life left.
When the engine continues to rev, or takes a few secounds to slow down to the slower spining trans, than it is just a matter of time before it needs to be replaced.
Marlin
Not being a smart
here so what your saying Marlin is wind it up to try and bark or get a second gear scratch and if it winds out with clutch out but don't seem to be accelerating much then you clutch is slipping ?
