Marksman14

Drove the car home today, starting the 3 heat cycles for break in that the recommend.

The gear is quiet as all hell, I couldnt tell any difference what so ever.

However, at 40 to maybe 50 mph (I couldnt get any faster that that, no room and its rainy here) I noticed a really low pitched humm coming from the back. Almost like a resonation of sorts. Its like if you did a speaker test, and got to the subwoofer and the volume was turned wayyy down.

I dont really see how a rear end could cause a hum like that, but ya never know.

Any ideas? I was expecting a whine...I get a low pitched hum. Go figure.

moosestang

Could be they put your drive shaft back on out of phase. I had a vibration over 70 after my gear install. I turned the drive shaft 90 degrees and it went away.

Derf00

did they mark the drive shaft before disconnecting it from the differential? Like moose said if they spun it and didn't put it back at exactly the same rotation position as it came off it could do that.

Marksman14

To be honest I didnt think to ask but that definitely makes sense.

Is this something that I could do easily at home?

jahudso2

i have the same noise at 60 mph after my 3.73 install. I don't remember my installer marking the d/s either.

Marksman14

Me thinks we both have a driveshaft rotation to be doing this weekend lol...

If you find a good how-to be sure to check back in, though I imagine it can't be too hard.

Scott

volcomchester18

The drive shaft comes marked from the factory with a yellow marking. I used to do gears at ford, you could try to turn the drive shaft but If that's not it. Then it wasn't installed right, or they didn't replace all the bearings like your supposed to. OR its just the nature of the 4.10 you should research on that. Gear whine is usually caused by improperly spacing the pinion gear, but humming noise sounds more like a bearing.

Derf00

If that doesn't resolve it then I would recommend the pinion angle be checked/adjusted. That is something a shop would have to do unless you have the specialized tool to do it yourself.

moosestang

Rotating the drive shaft isn't hard, but it can be tedious and time consuming to turn the rear of the shaft. There are 6 bolts that need to be removed and then reinstalled and you can only get to 2 at a time. You remove 2, then turn the driveshaft to get to the next 2. You'll need a torque wrench. The stock torque specs is only 41 ft lbs for these bolts. My shop cranked them down to way more than that, which probably causes some problems as well.

I'd recommend trying to turn it at the transmission first. It's easier to remove 4 bolts than 6, but you'll need to torque those to 76 ft lbs. Whatever you do, be sure to mark the thing with a sharpie or similar. If you clean it really well, then the sharpie should last a long time.

Marksman14

Yeah...really low pitched hum.

He said they could probably reuse all of the bearings except for possibly the pinion bearing. Once again, I failed to ask if they replaced it, but he said if they needed to they would, otherwise they'd be alright. My guess is that they reused them all....

I just figured if it was a bearing it would do it at all speeds, not just one small range. But obviously you know more about this than I do.

Long story short, If it doesn't disappear after the break in they recommended, its going back in. I'm not going to listen to any hum while Im driving. A gear whine would be less annoying to me than a low pitched hum.