This happened to me when i was putting in my longs. What i did was wrapped a chain around both outsides of the axle as close to the knuckle as possible and hooked the chain back to itself. Then I placed a floor jack inbetween the drooping part of the chain and the housing and when I jacked the jack up it pulled down on the outsides of the axle and straightened it enough to get my long in.. I'll try drawing you a diagram since this probally isn't wxplained too clearly..
