Rear end hum

[DarthMarauder]

I have replaced every bearing in the rear end. Put all new u-joints in and have new axles and seals. I still have a hum in my rear end. It used to be constant. After all that though now it doesnt start till around 50mph. The only thing I havent replaced it the gears. Can the gears cause a hum in the rear end? When I replaced everything they didnt look pitted or anything looked really good. Any thoughts?? May have to see if anyone wants to rid there 3.55's after going to 4.10s.

[Pat]

Tires can cause the hum you are experiencing. I've replaced my BFG's with Nitto's, hum gone (mostly).

Rear suspension components can also cause this by not keeping the tire "tight" against the road. However, this usually causes cupping in the tread.

[fastblackmerc]

Yes, gears can cause a hum or whine in the rear end if they are not setup correctly. You'll usually hear the humor whine when coasting.

Does the hum change when riding on a different surface ie. concrete or blacktop?

[DarthMarauder]

Tires can cause the hum you are experiencing. I've replaced my BFG's with Nitto's, hum gone (mostly).

Rear suspension components can also cause this by not keeping the tire "tight" against the road. However, this usually causes cupping in the tread.

That reminds me also forgot to add that I replaced the rear tires also they are brand new. Everything was done in a few day increments also. Axles and wheel bearings were first since I had the wheel seal blow and the axles were wore out (had the soft axles). Then came the pinion bearings, after that was the u-joints. Finally after that was the diff bearings and the new tires. Every time new fluid and friction modifier was used never reused it. Axles fixed the noise I had coming from there. Pinion fixed the constant hum and made it not start till 50mph. Then did the diff which made it a little quieter but its still very audible and I've gone a little deaf so if I can hear it its pretty loud.

[DarthMarauder]

Yes, gears can cause a hum or whine in the rear end if they are not setup correctly. You'll usually hear the humor whine when coasting.

Does the hum change when riding on a different surface ie. concrete or blacktop?

Hum does not change tones stays the same. Gears were never touched when hum started. Didnt mess with them till replacing the pinion bearing and everything was put back to where it was at. Had a master Ford mechanic help me with that.

[LeoVampire]

Like the pinion load was not done properly. It should be quiet as a church mouse if the gears and pinion are properly set.

[DarthMarauder]

Like the pinion load was not done properly. It should be quiet as a church mouse if the gears and pinion are properly set.

Does that just happen though cause the hum started when the gears had never been touched still as they were from the factory? The pinionbearing was touched to get rid of the noise which it did till 50mph. The Ford mechanic that helped me said that the pinion will hum starting at low speeds cause it spins fast and the diff bearing will be high speed but I never asked him about the gears. When I replaced the pinion bearings I'm thinking I fixed the low speed hum and now I'm having the high speed hum even though the diff bearings are new. Is there a certain speed the gears will start humming if they do??

[LeoVampire]

Get the ass end up and listen to the rear end with it in gear and turning see if you can isolate and or detect any noise.

Narrow it down somehow if you can. Ya I know without a load it is not easy to recreate something but it might be easier to pick it out outside of the car rather than in it.

It would have been a better idea to do it before changing things out but too late now.

Check the tires for cupping and see if they are running true as they are spining.

[fastblackmerc]

Hum does not change tones stays the same. Gears were never touched when hum started. Didnt mess with them till replacing the pinion and everything was put back to where it was at. Had a master Ford mechanic help me with that.

You didn't say you replaced the pinion in your original post. Did you also replace the ring gear?

Like LeoVampire said.... sounds like the pinion preload isn't set properly.

[DarthMarauder]

You didn't say you replaced the pinion in your original post. Did you also replace the ring gear?

Like LeoVampire said.... sounds like the pinion preload isn't set properly.

Sorry that was my fault meant pinion bearing. Gears are still factory. I'm wondering if I should just throw in some new gears since its the only thing left to replace in the drivetrain that could make the noise.

[scruff]

probally a good idea to bad you did,nt do it when you had everything opened up sounds like something is,nt lashed right check with a dial gauge before dismantle

[Stranger in the Black Sedan]

Another slightly noisy 8.8. New gears won't guarantee it's going to be quiet either so assess how much it bothers you. I started down this road when my 20k mile original gears were slightly noisy and 2 sets of gears later, it's exactly the same, very slight gear noise above 50 mph

Significant noise is the sign of a problem but a gear driven unit is always going to make SOME noise

[LeoVampire]

Did anyone look at the limited slip carrier and see if everything looked good in there?

[DarthMarauder]

Did anyone look at the limited slip carrier and see if everything looked good in there?

Everything seemed fine with the carrier very rarely drive her to hard and the clutches still grab. Can still spin both tires just as I could when she was new. I did have a little bit more than normal metal fragments but they were very small just made the fluid look metallic when I replaced the axles. After that fluid has been clean when changed. I'm thinking the metal fragments might of got my gears too. If I do get some new gears I will be replacing the clutches just so everything will be new and should not have to worry about it again.