04 Limited humming/howling sound

[BrandonH13]

Hi all, my wife and I just recently bought a 04 limited. We love it and it fits our needs with 3 kids. My wife is the one who usually drives it, but I drove it the other day and its making a kind of howling/humming noise from the rear...my guess the rear axle area. It seems to only make it from about 60 mph to 67ish mph. The speed limit is 70 on the highway where we live, so that could also be the reason why we have never noticed it before.
I am going to check the fluid in the axle, transfer case and tranny. Could this be a sign of the rear end going out? I really hope not, but figured I would ask here since I just found the site.

Thanks everyone.

 

[jrford]

most common culprit is the wheel bearings, i'd inspect those first. Check the Sticky thread above.

How many miles? What engine? Also post the Axle code, is it Open Diff or LSD?
LSD have been known to wear out but they usually cause tire hop or binding in the drivetrain.

 

[BrandonH13]

It has 1458xx miles on it. It also has a 4.6 V8 engine. How do I find out if it has the 3.55 or the 3.73 lsd? I havent crawled under to look on the axle itself

 

[02indyx]

There is an axle code on the label just inside the driver's side door.

http://www.explorerforum.com/forums/showthread.php?t=239360

 

[BrandonH13]

I'll look tonight since the wife is home and I am at work right now

 

[jakedrew]

probably the ring and pinion in the rear end. There is a TSB(technical service bulletin) for it.

To tell if it is the rear end do this: make sure it is warmed up( like 5-10 miles) . Get it up around 50-60 mph, let of the gas and get back on it slightly and listen. Do that a few times and if the howling comes and goes with you applying/letting off the gas then it is your rear end. If not it is a wheel bearing(common,my left rear went at 60k miles)

I havent heard of a rear end locking up or anything crazy like that, just making noise..

I had my rear end done at 55k miles at the ford shop under extended warranty. If I didnt have the extended warranty , the repair would have cost 1100$. They replace the ring and pinion and add thicker fluid which is 140w90 I think ,could be wrong.

 

[unclemeat]

Sound like a rear axle bearing to me.

 

[BrandonH13]

The sound does go away if I let off the gas and then comes back when I get back on the throttle. Like I said it seems to only do it around 60-65 mph.

I crawled under it today and I believe we have the limited slip. The tag says 3.73 and the 3 bottomish bolts were wet to the touch. Looks like someone has opened it up before because it looks like it has atv sealant instead of a gasket or maybe with a gasket.

We now have a new problem. The check engine light came on so I am going to have to run by a parts store so they can run the code for me. Hopefully its nothing big, but I will report back with what the code is for some help I am sure.

 

[Ronin8002]

These axles don't use gaskets anymore...you essentally make your own gasket out of RTV sealant.

 

[BrandonH13]

These axles don't use gaskets anymore...you essentally make your own gasket out of RTV sealant.

Thats what I meant was RTV lol. I will see what happens when I drive it tomorrow, but I plan on changing out all the fluids with fresh stuff soon anyhow. Tag says 75w-90 but I use 75w-140 in the rear right? Can I use that in the transfer case or should I stick to what the book says on everything else? Also since its the 3.73 I need to add limited slip additive correct?

 

[gsmornot]

If it has the limited slip you will need to add the modifier. There is a 3.73 open as well that will not need it. If you have the LS you should see a B6 under the axle code.

 

[BrandonH13]

This is why I am going to love this site.

I called 3 different ford dealers and told them my vin...all 3 said I had a 3.73 limited slip rear end.

The axle code on the door is a 46, V. Which would be a 3.73 open differental correct? That means I do not need the friction modifier and can just get some good old motorcraft 75-140 gear oil right?

 

[EasyRhino]

This is why I am going to love this site.

I called 3 different ford dealers and told them my vin...all 3 said I had a 3.73 limited slip rear end.

The axle code on the door is a 46, V. Which would be a 3.73 open differental correct? That means I do not need the friction modifier and can just get some good old motorcraft 75-140 gear oil right?

I used the Mobil 1 75W-140 that has friction modifier in it in mine at 100K miles.

I should add that mine has howled since new, and not gotten worse (or better even after changing the fluid). Now with about 112K miles, I'll drive it until it explodes, as has been reported on this site.

 

[04Explo]

Very good info here. I have a rear end howl that is ALWAYS there. No matter if I'm on the throttle or not. Sounds like the right rear wheel bearing but does not change sound when maneuvering right and left like most. Sounds like (whoo... whoo... whoo... whoo). And also kinda scrapes like a brake grind, but doesn't change when brakes are applied or when e-brake is applied slightly. So I assume it's Not the rear end...? I'm ok with having to fix it... but I bought this thing to replace another vehicle I had to constantly repair big things on. It would be nice if it's just brakes or a wheel bearing this time.

 

[dave12gauge]

Very good info here. I have a rear end howl that is ALWAYS there. No matter if I'm on the throttle or not. Sounds like the right rear wheel bearing but does not change sound when maneuvering right and left like most. Sounds like (whoo... whoo... whoo... whoo). And also kinda scrapes like a brake grind, but doesn't change when brakes are applied or when e-brake is applied slightly. So I assume it's Not the rear end...? I'm ok with having to fix it... but I bought this thing to replace another vehicle I had to constantly repair big things on. It would be nice if it's just brakes or a wheel bearing this time.

I just went through this on 03 limited 4wd v8. It was the bearings. From other posts on this site they said to use only timkin or skf bearings in an assembly. I had the mechanic also replace the cv axles since he had everything torn apart. My cv with the bad bearing was very hard to get off the bearing. I had 170k on all my running gear. I was luckier than most. If you have not change the rear end oil, use a HIGH quality 75w140 gear oil. I also thought that it was the right side bearing. Turns out it was the left side. Its funny how the sounds travel in the cab. I would also do both bearing, not just one. On mine the left was out, but the right one was rough and I'm sure it would have went out as soon as I would have left the shop. good luck

 

[04Explo]

I just went through this on 03 limited 4wd v8. It was the bearings. From other posts on this site they said to use only timkin or skf bearings in an assembly. I had the mechanic also replace the cv axles since he had everything torn apart. My cv with the bad bearing was very hard to get off the bearing. I had 170k on all my running gear. I was luckier than most. If you have not change the rear end oil, use a HIGH quality 75w140 gear oil. I also thought that it was the right side bearing. Turns out it was the left side. Its funny how the sounds travel in the cab. I would also do both bearing, not just one. On mine the left was out, but the right one was rough and I'm sure it would have went out as soon as I would have left the shop. good luck

Thank you Dave. I will post my results after the repairs are made.