i have a 87 ford bronco 4.9 stick (4spd) with traction lock. Truck started makeing a wining noise from the rear end. the pinion bearing was bad so i changed that and still makes this noise (also took entire carrier out and inspected for shaveings and cleaned what was found) but im thinking it is some bearing back there that is bad as it gets louder as the faster you go i was also told it could have pinion damage and will always make that noise (the noise is almost a ghetto supercharger noise. and is deep sounding but once i hit like 25 mph it makes a noise that is damn loud it sounds exactly like a lil electic motor that is having too much voltage runin thru it) thanks for all your help PLEASE POST ANYTHING THAT YOU THINK IT COULD BE (plz dot post stuff like "it sounds like there is something wrong") THANK YOU

 

Sounds like something is wrong alright! lol

With the noises that you are describing it could be the amount of lash between your pinion gear and the crown gear. I am not sure of the actual number for the min/max gear lash but you could probably get by talking to a mechanic at Ford. You'll need to either shim your pinion back to mesh more completely with the crown or pull a couple becaues it is riding on the inside of the gear.

Do you know how to check the gear lash?

 

My 95 Bronco did something very simliar. Would up the positrac unit went out and was eating up the spider gears in the differential. All of it had to be replaced.

To trouble shoot, we removed the rear drive shaft, put the rig into 4 wheel drive, and noted instantly the sound was gone. That drive shaft works well to transmit the sound from the differential back up to the cab. I wouldn't drive the bronco on the front axle only in 4x4 for very long though. Just long enough to test.

 

so here is the quistion what will it do if the pinion is spaced in correctly? will it lock up or just blow the gears all to hell? we had the entire rear end tore apart inspected it replaced the bearing and it still made the noise there was no indication of major wear/damage (except for the pinion seal/bearing beaing bad) i belive it is possible that the pinion gear was sloppen around so pinion damage/ware is possible (to a slight degree) and i have heard that once it does that it will always sound like that (auto zone says so lol) but also the noise was very minor when i first got it but then i went wheelin and i did pop it pretty had in 1st low (dumb i know but i did it) and that's when the pinion seal/bearing went out (that there may be key in to why it does it) all your help is apprisheated thanks in advance =)

 

When you put it back together, did you set the pinion bearing pre-load correctly? If you didn't use an inch-lb torque wrench, a collapsible spacer, and something to hold the flange while you put about 200 lb-ft of torque on the pinion nut, then that's likely the problem.