So, I've been hearing a moaning sound when accelerating coming from the rear. Going to start with U joints as the sound is now changing to a chirping/squeal. And it seems to be the cheapest parts to replace.
This is a 5.4 with 4x4 and 139 wheel base with Super cab. The sticker doesn't say if this is a 9.75 diff but it is a 12 bolt.

Also not sure which size bearing caps are in the u joints. This is a 2 joint drive shaft. On Advanced Auto and Rock Auto, they offer two different sizes.
I noticed there may be some leakage coming from the drivers side bearing. I didn't tear it down since I don't have any parts yet.
Would at least like to replace u joints to accomplish something. Has 115,000 miles on it.

 

Does the sound go away when you let off the gas?
If it does check the yoke and see if it is loose. Best way to do this is jack the whole rear up (Place on jack stands and not just a jack by its self ) and try to move the shaft up and down.
How many miles are on the 9.75 rear-end?

Now for the bad news:
If the u-joints are good as well as the yolk nut tight (If loose then you will have to replace the nut and set it up) if they are good then you have one or both bearings going out on the pinion or carrier bears one each side or both. (Most times it pits on the race or bearings from water getting in the system or bad bearings for that type of sound and not a tooth cracked on a gear).

The easiest way to fix it is to order a rebuild kit of bearings, shims, spacers, and gasket as the inner bearing for the pinion is around 200.00 dollars at Orielly's, Advance and all those for a 9.75. (Ford price is around 100.00 for that one bearing). The kit is less than 200.00 and it comes with the bearings, spacers and two nuts for the pinion. (One nut is to set up the pinion preload. (These nuts can only be used 1 time and 1 time only or they will backoff).

You will need a fish scale torque to watch the nettle move to 10" pounds and not a regular torque wrench as they cannot show this. If you have never done it before I can help you build one with the kit and write you though it. If it is your first time there are things you will have to do. If you only have to replace the bearings the backlash should be ok and you would not have to have a dial indicator to show the thousands inch movement if you set it up with the same shims that were in it or if one is broken place the same amount of shims thousands on that side. Take pictures before, during and after.

I hope that helps.

 

The sound goes away when off the gas. Sometimes does it in reverse but I am not going very fast backwards.
I've seen a couple videos on how to tear it all down. I just don't have the tools or cash to do a full rebuild. Hoping to work on it this weekend to see if it's more than u joints.
The most I would do is wheel bearings and pinion bearing.
My main concern is which u joints do I need? Seems to be two sizes of bearing caps for all options. 1 1/16 or 1 3/16
Assuming I have the larger one with a 9.75 rear and 4x4.

 

Take a good look at your carrier bearing. It is the one where the two drive shafts come together and hold them up to the truck. When they go bad they also make a sound like the rear end is going bad. I am thinking now after you said it makes noise in reverse that it may be your problem. Place the truck on jack stands where the rear wheels are off the ground and place the transmission in neutral front wheels blocked so it will not roll. Now get under the truck and have someone turn the rear wheels and watch that bearing and driveshaft. You can turn it by just twisting the driveshaft also and move it up and down and see how much play you have. Make sure the bearing is not turning inside the plastic-like rubber stuff that is holding it. If the rubber-like is broken or torn and not a burn brown look if so you have to replace it. These things go bad a lot and will drive you mad trying to find out the problem and they do make a sound from a hum to a screech sound.

Go to this link and see what one looks like if you don't know.
https://www.google.com/search?hl=en&...30.MF_SG0ZB2d4

 

You are going to have to crawl under there and grab on to the of the driveshaft near the joint and wiggle it. Usually the rear one goes belly up first, in my experience.

 

All you have do is measure the cup size, the smaller one is 1.063 and the other one is 1.88. You can do it from the outside of the yoke. If it's FX4 it will have bigger one.

Denny

 

I don't have a carrier bearing. This is a 2 joint drive shaft. 1 at the transfer case, the other at the diff. There is no carrier in between.
It is not an FX4 but a 4x4 with off road package.

 

Just measure the cup to get the right joint.

Denny

 

You can take the rear drive shaft mounting bolts off in about 15 minutes... then slide the shaft out of the transmission....rotate both U joints by hand and feel for stiffness, dragging, or slop.... I went to the Auto Store AFTER I determined the drive shaft was the cause of the noise. You have a press or something to get the u-joint caps off ?

 

with the drive shaft OFF.... is the time to check pinion slop / back lash / radial clearance.

 

As steve suggested, removing the driveshaft is best. It's the only way to tell if a u-joint is just starting to fail. As you rotate the joint you'll be able to feel if there is tightness or slop. You will also be able to feel notching which indicates the bearing surface has brinelling starting. If you haven't removed these driveshafts before, a hint is the bolts are loctited in. Just use a propane torch to heat the bolt / flange area to soften the loctite. Be careful not to torch the flange seal.

 

It's my project for the weekend. I had the drive shaft off many years ago when I replaced the transmission. I remember buying a 12pt wrench just for these bolts.
Been meaning to grease up the yoke shaft for a while too. So hope I can find some answers soon. My local parts stores have the u-joints in stock. I can borrow a ball joint press from autozone to get them out. I also have a BF bench vise to try to press them out using sockets if need be. Should be ok on that part. Thanks!

 

I use a big 5 lb hammer and impact sockets to get them out, the new ones go back easy.

Denny

 

It was the rear u-joint that had a 'dry cup'. Along with what was left of the right rear brake pads.
All fixed up and ready to roll. Thanks for all the suggestions.

btw bearing cups were 1 3/16"