[FST FOX]

Since I put the car together I have been working out little bugs, last night with probably 500 miles on it it started shaking from the rear pretty violently when starting out in 1 and 2nd after 3rd it was fine, I remeber I had little clearance from the frame to the front of the driveshaft, I was told to mount the cross member below the crossmember bracket instead of above it. I am about to drive the car onto ramps and look at whats going on, but I am also going to change the rear end fluid, what fluid is reconmended for these rear ends and alsoany helpful tips would be nice.