Only condition where I am getting a zipping-type of grind: In 4th gear when going up an incline. Around 50-60mph. And it only happens randomly, not all the time. Mind you, it doesn't grind while shifting, it suddenly starts grinding (sounds like a big heavy zipper) while in 4th gear when driving up a slight incline. Seldomly occurs on flat road, too (Not much flat road in my area, though). My guess would be maybe weak detent allowing gear to contact synchro/blocker rings?? What do you think forum?