As the title states, im getting an unusual clunk when i shift from 4th to 5th on my manual 07 GT. I'm completely new to mustangs and picked up this car a month ago. I have read some people stating that it could be a U joint issue but that problem seems to be only prevalent for people when starting off. My issue is when shifting from 4th to 5th, at generally any RPM, i get a nasty sounding clunk. Initially i thought it could be just how im slipping the clutch or slack in the transmission. I tried slipping the clutch different ways, faster slower, more rpms, less rpms, and still about 7/10 times i get that sound. If i really, really focus on matching everything perfectly when i shift, its a little less prevalent but generally the sound is always there.
Could someone tell me what im up agains? Is it a U joint issue? Messed up rear differential? Is this just a normal sound or is it just because im not shifting right into that gear? I hate driving with people in the car at anything faster than 40mph because i know that when i shift, i will likely get that awful sound.