i just replaced my axles and now during acceleration (heavy or light) it vibrates badly and is kinda shakey. could this be just bad axles? (unbalanced) i have not got an alignment yet though as well. could that be it? also its manly in 2nd and 3rd gears. theres barely any in 1st 4th n 5th unless i floor it , but theres still very little vibration.

also im running headers and cats only, nothing else. could the vibration be from that? i wouldnt think it would be thanks guys

 

double check all your nuts and bolts, something might be loose.
Make sure the axle is in the tranny tight.
If all these things check out, have the axle inspected
Could also be as simple as a tire needs balanced.