A few years ago the 3.55 gears (8 3/4 489) in my '72 Cuda started howling when cruising along at 45-65mph, although it hasn't gotten any louder. I was afraid of causing more damage to the rear end so I recently swapped the 3rd member out for a 4.30 pumpkin I had laying around. This setup is really fun around town but is killing me at the gas station so I was thinking of swapping it back. My question is whether the howling rear end will eventually destroy itself or is it safe to keep running? I can deal with the noise but I just don't want to get stranded with a broken rear end someday. I'm half tempted to rebuild the current 3.55 with a new gear set, seals and bearings, but I've never tackled something like that before.