Just changed diff oil
Thread Starter
Le Mans Master
Joined: Dec 2004
Posts: 5,759
Likes: 539
From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Just changed diff oil
And noticed something a little unusual. While taking out the fill plug, the diff started sucking air. At least that is what is sounded like to me, I guess it could have been pressurized but my gut feeling was that it was under a slight vacuum.
The drain plug is a bear to get to. Sits right above the transverse spring. I had to modify a hex head socket and use a "wobble" extension to get to it.
The diff oil was dirtier than I would have suspected for only having 8500 miles on her.
Lastly, it did seem to cure the "moan" or "groan" that has been mentioned in the TSB. TIme will tell.
Anyone else have this happen to them?
The drain plug is a bear to get to. Sits right above the transverse spring. I had to modify a hex head socket and use a "wobble" extension to get to it.
The diff oil was dirtier than I would have suspected for only having 8500 miles on her.
Lastly, it did seem to cure the "moan" or "groan" that has been mentioned in the TSB. TIme will tell.
Anyone else have this happen to them?
Thread Starter
Le Mans Master
Joined: Dec 2004
Posts: 5,759
Likes: 539
From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Used Amsoil Sever Gear 75W-90 and a bottle of the GM additive for the limited slip diffs. Amsoil says you may not need it but I did it. If you do the additive, make sure you shake up the bottle real good. The bottle indicates some settling may have occured and my bottle did.
Racer
Joined: Oct 2005
Posts: 439
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From: TAMPA BAY FLORIDA
I'am sure that there are forum members with far more expereince with additives but I have used Amsoil without the addtional friction modifier.My concern was that it might decrease the locking ability. If the noise you heard was especially noticeable when making turns it might have been the differential prematurely locking up.
Drifting
Joined: Jun 2005
Posts: 1,837
Likes: 4
Mine seemed pretty dirty too, at 3K miles. I don't recall it sucking, but that's not too hard to believe. Probably some sort of vent, that may release pressure but not allow air back in.
A Bondhus ball-end hex wrench http://www.bondhus.com/products/l-wrenches/body32.htm or Snap-On long ball ended hex socket http://buy1.snapon.com/catalog/item....re&dir=catalog makes this job a lot easier.
Some folks recommend adding just as much friction modifier as needed, starting with none and adding it in one-ounce increments if chattering is heard.
A Bondhus ball-end hex wrench http://www.bondhus.com/products/l-wrenches/body32.htm or Snap-On long ball ended hex socket http://buy1.snapon.com/catalog/item....re&dir=catalog makes this job a lot easier.
Some folks recommend adding just as much friction modifier as needed, starting with none and adding it in one-ounce increments if chattering is heard.
Last edited by Buffy; Dec 23, 2005 at 11:55 AM.
Team Owner
Joined: Feb 2000
Posts: 53,520
Likes: 77
From: Arizona
Originally Posted by ByByBMW
And noticed something a little unusual. While taking out the fill plug, the diff started sucking air. At least that is what is sounded like to me, I guess it could have been pressurized but my gut feeling was that it was under a slight vacuum.
Anyone else have this happen to them?
Anyone else have this happen to them?
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
Originally Posted by ByByBMW
And noticed something a little unusual. While taking out the fill plug, the diff started sucking air. At least that is what is sounded like to me, I guess it could have been pressurized but my gut feeling was that it was under a slight vacuum.
The drain plug is a bear to get to. Sits right above the transverse spring. I had to modify a hex head socket and use a "wobble" extension to get to it.
The diff oil was dirtier than I would have suspected for only having 8500 miles on her.
Lastly, it did seem to cure the "moan" or "groan" that has been mentioned in the TSB. TIme will tell.
Anyone else have this happen to them?
The drain plug is a bear to get to. Sits right above the transverse spring. I had to modify a hex head socket and use a "wobble" extension to get to it.
The diff oil was dirtier than I would have suspected for only having 8500 miles on her.
Lastly, it did seem to cure the "moan" or "groan" that has been mentioned in the TSB. TIme will tell.
Anyone else have this happen to them?
Glad to see the fluid helped the moan.
As an FYI, I don't add the friction modifier to my diff as it doesn't chatter. By adding too much friction modifier, it won't hurt anything, but the ability of the friction plates to provide the right amount of limited slip will be slighly diminished. So you might notice more inside tire wheelspin under hard acceleration from tight corners. Not anything to lose sleep about on the street, but would hurt acceleration on the track.
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C66 Racing #66 NASA ST2, SCCA T2
AMSOIL Dealer (Forum Vendor)
AMSOIL Preferred Customer Program (Members buy at Wholesale - a savings of about 25%)
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Joined: Aug 2001
Posts: 5,364
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From: King George VA
Originally Posted by KAIROS
what fluid did you use as a replacement?
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
AMSOIL also makes a friction modifier, but as mentioned above, I don't use it:
AMSOIL Slip-Lock Differential Additive
If you do your own fluid changes, this comes in handy for AMSOIL bottles as it screws right onto them and has a higher capacity per pump than the ones I've bought in local autoparts stores:
AMSOIL Hand Pump
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Thread Starter
Le Mans Master
Joined: Dec 2004
Posts: 5,759
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From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by Subdriver
The pressure release sound is normal and nothing to worry about. What happens is that as the diff gets hot, the fluid expands and the pressure relieve valve on the top driver's side of the diff vents the pressure off. When you stop driving, the fluid cools and contracts, but the vent seals preventing air and moisture from coming in, hence a slight vacuum develops.
Glad to see the fluid helped the moan.
As an FYI, I don't add the friction modifier to my diff as it doesn't chatter. By adding too much friction modifier, it won't hurt anything, but the ability of the friction plates to provide the right amount of limited slip will be slighly diminished. So you might notice more inside tire wheelspin under hard acceleration from tight corners. Not anything to lose sleep about on the street, but would hurt acceleration on the track.
Glad to see the fluid helped the moan.
As an FYI, I don't add the friction modifier to my diff as it doesn't chatter. By adding too much friction modifier, it won't hurt anything, but the ability of the friction plates to provide the right amount of limited slip will be slighly diminished. So you might notice more inside tire wheelspin under hard acceleration from tight corners. Not anything to lose sleep about on the street, but would hurt acceleration on the track.
Le Mans Master
Joined: Jan 2005
Posts: 5,611
Likes: 5
From: Thousand Oaks California
Originally Posted by Buffy
A Bondhus ball-end hex wrench http://www.bondhus.com/products/l-wrenches/body32.htm or Snap-On long ball ended hex socket http://buy1.snapon.com/catalog/item....re&dir=catalog makes this job a lot easier.
The differential drain and fill plug is not a "hex". It requires a Torx T55 bit. A hex tool can deform the plug so that you will not be able to insert the correct T55 Torx bit and may strip out the plug. Always use the correct tool.
Last edited by calemasters; Dec 23, 2005 at 09:34 PM.
Thread Starter
Le Mans Master
Joined: Dec 2004
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From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by calemasters
The differential drain and fill plug is not a "hex". It requires a Torx T55 bit. A hex tool can deform the plug so that you will not be able to insert the correct T55 Torx bit and may strip out the plug. Always use the correct tool.
HOWEVER. I have been only a backyard mechanic, no real formal training except for my 16 years in the Navy as a machinist mate. And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
I would recommend anyone that wants to do this, go look at your plug then buy either the torx or the allen/hex head, whichever is correct for your diff. (My money is on hex head)
Respectfully
bybyBMW
PS My BMW's all had hex head plugs also. Just larger, 17mm vice 10 for the C6.
Premium Supporting Vendor
Joined: Aug 2001
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From: King George VA
Originally Posted by ByByBMW
... And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
Premium Supporting Vendor
Joined: Aug 2001
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From: King George VA
Originally Posted by ByByBMW
I did get the pump, only problem is it blew the hose off so am going to put one of those plastic clamps on it to help keep it on. Made quite the mess.
I can imagine what a mess that made. Gear oil is smelly stuff too. My wife hates it when I change the diff fluid. She won't come near the garage when I do that.
Team Owner
Joined: Oct 2004
Posts: 27,420
Likes: 64
From: San Clemente CA
Originally Posted by ByByBMW
I must respectfully disagree with you, and that is a mighty big undertaking after looking at your public profile. Engineering and auto business. Very nice.
HOWEVER. I have been only a backyard mechanic, no real formal training except for my 16 years in the Navy as a machinist mate. And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
I would recommend anyone that wants to do this, go look at your plug then buy either the torx or the allen/hex head, whichever is correct for your diff. (My money is on hex head)
Respectfully
bybyBMW
PS My BMW's all had hex head plugs also. Just larger, 17mm vice 10 for the C6.
HOWEVER. I have been only a backyard mechanic, no real formal training except for my 16 years in the Navy as a machinist mate. And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
I would recommend anyone that wants to do this, go look at your plug then buy either the torx or the allen/hex head, whichever is correct for your diff. (My money is on hex head)
Respectfully
bybyBMW
PS My BMW's all had hex head plugs also. Just larger, 17mm vice 10 for the C6.
Check the owners manual page 5-43 and it show's a allen/hex head. I have been working on cars for over 50 years and that is all I have seen.
Thread Starter
Le Mans Master
Joined: Dec 2004
Posts: 5,759
Likes: 539
From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by own2vettes
I'm just curious. Why are you guys changing your rear diff fluid?
Safety Car
Joined: Jul 2004
Posts: 3,867
Likes: 307
From: Wantagh,L.I. New York
Originally Posted by ByByBMW
I must respectfully disagree with you, and that is a mighty big undertaking after looking at your public profile. Engineering and auto business. Very nice.
HOWEVER. I have been only a backyard mechanic, no real formal training except for my 16 years in the Navy as a machinist mate. And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
I would recommend anyone that wants to do this, go look at your plug then buy either the torx or the allen/hex head, whichever is correct for your diff. (My money is on hex head)
Respectfully
PS My BMW's all had hex head plugs also. Just larger, 17mm vice 10 for the C6.
HOWEVER. I have been only a backyard mechanic, no real formal training except for my 16 years in the Navy as a machinist mate. And I have to tell you, maybe your drain plugs are Torx, but mine are definitely 10mm Hex, or allen head if you prefer. All my torx bits in my toolbox are a "star" shape. My plug is definitley a hex head, i.e. flat on all 6 sides.
I would recommend anyone that wants to do this, go look at your plug then buy either the torx or the allen/hex head, whichever is correct for your diff. (My money is on hex head)
Respectfully
PS My BMW's all had hex head plugs also. Just larger, 17mm vice 10 for the C6.
Le Mans Master
Joined: Jan 2005
Posts: 5,611
Likes: 5
From: Thousand Oaks California
You guys caught me!
My differential plugs are somewhat deformed on the corners of the hex insert. The deformation, or rounding off, makes the opening appear to be a Torx (sort of), but it looks like if I had a "new" plug, it would be a true hex. I hate it when I'm wrong. 
Fill Plug:
Drain Plug:
Like I said, alway use the correct tool, use a 10 mm hex.
Fill Plug:
Drain Plug:
Like I said, alway use the correct tool, use a 10 mm hex.
Last edited by calemasters; Dec 25, 2005 at 06:02 PM.
Thread Starter
Le Mans Master
Joined: Dec 2004
Posts: 5,759
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From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by calemasters
My differential plugs are somewhat deformed on the corners of the hex insert. The deformation, or rounding off, makes the opening appear to be a Torx (sort of), but it looks like if I had a "new" plug, it would be a true hex. I hate it when I'm wrong.
Like I said, alway use the correct tool, use a 10 mm hex.
Like I said, alway use the correct tool, use a 10 mm hex.
Gee, I've never been wrong before. Only about 5e+10 times or so, and that was just in the last year.
Thanks for checking your car and