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Discussion Starter · #1 ·
Over the last few weeks I have been hearing this strange noise coming from what I think to be the back of the car. You feel it in the whole car and there is this like moan and rubbing/grinding sound. I first felt it pulling into the driveway and into parking spots. It seems to have progressively gotten worse and now I feel it just making a normal turn sometimes. It didnt seem too bad and it would not happen consistently. Now it happens either way I turn and its getting louder. I have run out of ideas on what this could be. I have checked the clearance of the rear wheels, checked the clearance of the exhaust for rubbing on the tire. I got the rear end rebuilt last July with an Eaton Posi and new 3.73 gears so im really hoping its not the rear again, although I dont know what else it would be. Any help would be appreciated.
 

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I'm only guessing here, but it sounds like the axle bearings. Yes, you would need to rebuild the rear end again, but most times a gear change does not include a new set of axle bearings, because you have to pull the entire axle out to get to them, I think.
 

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It sounds like sticky clutch packs to me. You might be able to address this situation with friction modifier rather than replacing those.
 

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From what I know, you could just slide the axles out of the way to replace the carrier bearings, but not replace the axle bearings.

On a side note, Tony may be correct. It will be a bunch cheaper to have the correct friction modifier added to the gear oil than replacing the axle bearings. You may want to give that a try first.

Are you in good enough with the shop to have them take a listen? Maybe a trained ear is what you need.
 

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Discussion Starter · #6 ·
I took the car to a shop for an alignment after lowering it. I had never been to that shop and I talked to them about the sound I was getting. He recommended a gear oil change because he said the clutch dust from the rear end can cause all kinds of sounds when it builds up in there. I had them drain and clean the rear end out and refill with new fluid and the Ford friction modifier. It didnt help right away but after the ride home and a few hours of sitting I went for a ride and the sound seems to be completely gone!!! I am so glad that seemed to solve the problem
 

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Discussion Starter · #7 ·
I am bringing this one back from the dead, as i never updated it to say that it was NOT fixed from the friction modifier, I just could not hear it because it doesn't start doing it until you drive for 5-10 min. So 2 months later its in the shop that rebuilt the rear end. They checked all bearings and they have normal wear patterns and the axles look fine as well. You cannot see inside the differential housing so they talked to several people including the distributer of the Eaton units and they all agree that it is the clutch packs binding. The unit has to be shipped out to have new clutch packs in and then I get to pay for a rear end install again YAY!!

My question to you guys is, if the clutch packs are the problem, would you expect that to be from a faulty clutch pack or a bad install? The main reason behind this is wondering if I should be going after the shop for a bad install or what. Of course the Eaton warranty on the unit is only a year and its been a year and 5 months. I would love to hear what you guys think. Thanks
 

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Discussion Starter · #9 ·
I talked to an engineer from Eaton today and they told me that it is the synthetic gear oil used from the time the differential was installed that damaged the clutches. The synthetic oil causes the carbon clutches to bind and not work the way they are supposed to. They said mineral based oil must be used. I will be talking to the shop tomorrow and will not be paying for them not using the right gear oil. It says right on the differential box that synthetic oil is not recommended and gives a recommended oil.
 

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installermarc said:
From what I know, you could just slide the axles out of the way to replace the carrier bearings, but not replace the axle bearings.

On a side note, Tony may be correct. It will be a bunch cheaper to have the correct friction modifier added to the gear oil than replacing the axle bearings. You may want to give that a try first.

Are you in good enough with the shop to have them take a listen? Maybe a trained ear is what you need.

its the other way around on the bearings. you can slide the axle all the way out and get to the axle bearings, they are the ones at the end of the tubes. the carrier bearings you have to remove the differential and pull the bearings off and then press new ones on.

also to the op it sounds imo as if the shop who did the install is at fault for using incorrect fluid.

to anyone who has clutch packs done on the oe differential. soak your clutch discs for about 30mins in friction modifier
 

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WOW this news really sucks... I have the same exact rear end setup and have been having the same noise. Thanks for letting me know whats wrong though. Just need another $500 for the install i guess.
 

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Discussion Starter · #12 ·
UPDATE: my car has been in the shop for 2 and a half weeks now. perfect timing with the holiday made for an extended time in having the differential sent out to get new clutch packs installed. I talked to the installer about the fluid and they seemed very genuine when they said they never use synthetic with the Eatons. They do a ton of them and I do believe they know this and did not do it and just mentioned the Royal Purple to me some time by accident. If you didnt read the one post above, the bearings are not the problem, they all look perfectly fine and so do the axles. The Bullitt has been inside the shop just sitting there with the rear end disassembled for 2 weeks, waiting for the differential to get back to the shop. A new set of 4.10s will be put in when it comes in and I will have a brand new rear end AGAIN!!! Still waiting on the final verdict for the price, hoping I get a little break on the labor, we shall see. I hope its done tomorrow, going through Bullitt withdrawal.
 

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Bullitt2436KM said:
UPDATE: my car has been in the shop for 2 and a half weeks now. perfect timing with the holiday made for an extended time in having the differential sent out to get new clutch packs installed. I talked to the installer about the fluid and they seemed very genuine when they said they never use synthetic with the Eatons. They do a ton of them and I do believe they know this and did not do it and just mentioned the Royal Purple to me some time by accident. If you didnt read the one post above, the bearings are not the problem, they all look perfectly fine and so do the axles. The Bullitt has been inside the shop just sitting there with the rear end disassembled for 2 weeks, waiting for the differential to get back to the shop. A new set of 4.10s will be put in when it comes in and I will have a brand new rear end AGAIN!!! Still waiting on the final verdict for the price, hoping I get a little break on the labor, we shall see. I hope its done tomorrow, going through Bullitt withdrawal.
i read that it wasn't bearings, i just stated that for future reference
 
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