2000 Ford Mustang GT 4.6 - Rear Differential

Misti

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Jun 23, 2019
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Doniphan Mo
I Have Noticed Dark fluid leaking! It's in the back and I finally Investigated and Found this! I added a photo! So I bought a New Gasket and some Gear Oil to go with it! So I think I'm going to be changing this Gasket and figuring out how and why its bent like that. How do I get it out and do I just take a hammer to it?
 

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stormsedge

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It looks like a jack was put in the wrong place and bent the cover lip up...alternatively, the car was driven over something high enough to bend the cover back, but it really looks like it was "lifted" from below. In any event, you might first try tightening the cover bolts a bit---don't overtorque them---to see if it stops the leak (if it does, top your diff oil off). If not, covers can be had fairly cheap from salvage, or from aftermarket suppliers. With that in mind, if tightening it doesn't stop the leak, there is no reason not to work it a little with a hammer to try and get a straight edge for a seal(use a straight edge to judge your work...ALSo, check to see if the cover is cracked. The hardest part of this job for me was figuring out a good way to get the oil back in it...a lot of obstructions on the front side, especially when trying to get the diff level...I finally fell back to a piece of hose jammed on the gear oil bottle nozzle. Note that OEM was put on with silicone gasket goo (no gasket), so when you put a gasket in there you get some extra crush that will help seal your diff if the cover is a tiny bit off. ((And diff oil stinks...try not to get it on you)). Have fun!

Edit...reread your post...get the car safely on jack stands...basically put a large catch pan under the diff cover area and loosen the bolts enough to allow the cover to separate from the diff to let the old oil out. There is a 1/2" square head plug on the driver's side front---the oil goes back in there once the cover and new gasket are installed. Try to get the car/diff level and fill the diff until the oil is even with the bottom of the fill hole (it will seep out when you are there).
 
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Misti

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Jun 23, 2019
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Doniphan Mo
It looks like a jack was put in the wrong place and bent the cover lip up...alternatively, the car was driven over something high enough to bend the cover back, but it really looks like it was "lifted" from below. In any event, you might first try tightening the cover bolts a bit---don't overtorque them---to see if it stops the leak (if it does, top your diff oil off). If not, covers can be had fairly cheap from salvage, or from aftermarket suppliers. With that in mind, if tightening it doesn't stop the leak, there is no reason not to work it a little with a hammer to try and get a straight edge for a seal(use a straight edge to judge your work...ALSo, check to see if the cover is cracked. The hardest part of this job for me was figuring out a good way to get the oil back in it...a lot of obstructions on the front side, especially when trying to get the diff level...I finally fell back to a piece of hose jammed on the gear oil bottle nozzle. Note that OEM was put on with silicone gasket goo (no gasket), so when you put a gasket in there you get some extra crush that will help seal your diff if the cover is a tiny bit off. ((And diff oil stinks...try not to get it on you)). Have fun!

Edit...reread your post...get the car safely on jack stands...basically put a large catch pan under the diff cover area and loosen the bolts enough to allow the cover to separate from the diff to let the old oil out. There is a 1/2" square head plug on the driver's side front---the oil goes back in there once the cover and new gasket are installed. Try to get the car/diff level and fill the diff until the oil is even with the bottom of the fill hole (it will seep out when you are there).
Ok, I am working on this at the moment! I'm kinda worried but Hopefully I can handle this one. I also read online about something in 4 oz. Called or said "Friction " to add with my gear oil! Is this true?
 

stormsedge

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Ok, I am working on this at the moment! I'm kinda worried but Hopefully I can handle this one. I also read online about something in 4 oz. Called or said "Friction " to add with my gear oil! Is this true?

You are referring to Ford Racing Additive Friction Modifier...comes in a 3.8 ounce plastic bottle...~$12. Used for posi rears and helps keep down chatter. I used it in mine, but the Royal Purple gear oil I used indicated it was not needed on their container, and indeed, some folks here do not use it. I guess it really depends on the grade of gear oil you have, what their claim is, and then make your best choice.
 
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Misti

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You are referring to Ford Racing Additive Friction Modifier...comes in a 3.8 ounce plastic bottle...~$12. Used for posi rears and helps keep down chatter. I used it in mine, but the Royal Purple gear oil I used indicated it was not needed on their container, and indeed, some folks here do not use it. I guess it really depends on the grade of gear oil you have, what their claim is, and then make your best choice.
Ok, That makes Good Sense! Thank You very Much! I appreciate your time in answering my questions!
 

Misti

Member
Jun 23, 2019
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Doniphan Mo
You are referring to Ford Racing Additive Friction Modifier...comes in a 3.8 ounce plastic bottle...~$12. Used for posi rears and helps keep down chatter. I used it in mine, but the Royal Purple gear oil I used indicated it was not needed on their container, and indeed, some folks here do not use it. I guess it really depends on the grade of gear oil you have, what their claim is, and then make your best choice.
Ok, That makes Good Sense! Thank You very Much! I appreciate your time in answering my questions!
I do have one more question! What is this on there that looks like a cap? I added a picture!
 

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stormsedge

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I do have one more question! What is this on there that looks like a cap? I added a picture!

That is the rear axle vent bolt...it's purpose is to prevent pressure from building inside the rear diff/axle housing that would eventually cause leaks. Your leak is likely not this, as you have identified the gooned cover. Enjoy.
 
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Misti

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That is the rear axle vent bolt...it's purpose is to prevent pressure from building inside the rear diff/axle housing that would eventually cause leaks. Your leak is likely not this, as you have identified the gooned cover. Enjoy.
I fixed the leak! That was very easy! Everything went so Well. I Even took a few pictures of the inside of my differential! I straightened out the plate that was bent! Placed a New seal! I bought a pump to help put fluid back into it! That was a huge help! I appreciate all the help and info about this issue I was having with my car! I'm excited that its officially fixed! Thank You Very much!
 

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Olivethefet

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In that last pic you have the car on a jack stand and I can see a jack on the other side. Did you have two jack stands under the car or were you using the jack to hold up one side of the car while you worked on it?
 

Noobz347

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In that last pic you have the car on a jack stand and I can see a jack on the other side. Did you have two jack stands under the car or were you using the jack to hold up one side of the car while you worked on it?


If so, that is a nono :nono:

--and--


This guy calls it out in [every] image so...


Get more jack-stands. Yellow, bright orange, or fire engine red show up best in pictures. :nice:
 

stormsedge

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Jun 17, 2018
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I fixed the leak! That was very easy! Everything went so Well. I Even took a few pictures of the inside of my differential! I straightened out the plate that was bent! Placed a New seal! I bought a pump to help put fluid back into it! That was a huge help! I appreciate all the help and info about this issue I was having with my car! I'm excited that its officially fixed! Thank You Very much!

Super! I'm happy it went well...a pump was smart!