Hey i went out to the 1/8 mile tonight and ran 7 times on my 7th rn I relized I had a knock when I disengaged the clutch into the next gear. So on my way home I would get going about 45 in 3rd and blurp or stomp the throttle but not all the way to the floor and it was like there is slack for lack of a better work in my diff.. like there is a delay and then it makes a knock sound and catches and it does it in all gears so I don't belive it's my tranny wich is fairly new. Any help please

 

I have a 86 gxl wich is a part car if you guys thinks its in my diff then should I just switch them?