so i was having a bad leak for a while on the drivers side rear wheel... knew it was the axle oil seal, so i bought the parts and was gonna pull the axles and replace them myself. unfortunately, the p.o.s pinon shaft lock bolt snapped as soon as i tried to back it out. i had no choice at that moment but to put everything back together and abort my attempted fix.

then in august finally decided to try and fix the leaking seal again, but have ford do it. since the diff would be open anyway, i bought FRPP 3.73 gears and a motive gear install kit and took it to ford to have the install done.

they quoted me 900 to replace the seal and do all the gear/diff work since they anticipated extra labor to extract the broken bolt, and i left them the parts.

a few days later, i get a call saying the quote is now 1500!! because it took even more labor than they anticipated to extract that bolt. they had to replace the pinon shaft as a part of the process but that was only 40 bucks so whatever.

they also said the rear wheel bearings were worn after 80000 miles. so, even though they werent making any noise, i agreed after talking them into doing it for free since their original quote was off by so much.

she pulls even harder now and im really satisfied with the performance/fuel econ tradeoff of the 3.73s. however, only after did i learn i couldve bought a brand new LSD with all the carbon plates and stuff (including a non-f'ed up pinon shaft and lock bolt) for just over 200 bucks....

the problem now is that the freshly rebuild rear end makes more noise than it did before! (used to be a slight gear whine on decel). theres still a hint of whine (this time on accel from about 50-60mph) which is nbd, but theres another noise....

with the windows up and no music/loud fan, i can hear what id describe as a coarse hiss that im pretty sure is coming from the rear end. whats odd is that it sounds like it has the same pitch from when it first becomes audible around 30mph all the way up to 90mph when it becomes drowned out by my exhaust and wind noise. this is unlike the gear noise (or any other noise i can think of) where the pitch varies with the speed. also of note is that with the windows down when im coasting along side a wall or tall curb i can hear a faint hiss as well.

again, every moving part in the rearend is new, and ive taken the brakes apart and cleaned them, and now im out of ideas.

so, any ideas? bad wheel bearings? dragging brake? bad bearings/gears?

any suggestions would be great, thanks in advance.

p.s. this is my first post on the forum haha

 

That hiss could be a pinion bearing or even a seal issue. Not gonna be easy to find though. Could be something at one of the rear brakes also. Needs to be ran on a rack in the air to pinpoint it.

 

thats a good idea i didnt think of that. do u think itd be ok if the rear was on jack stands or should i get the whole car up on a 4 point lift?

 

I would just be very careful doing that. Make sure the traction control is off too. May not let you accelerate if not.