Rear Differential Fluid Issue
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
Likes: 232
From: SoCal
Rear Differential Fluid Issue
Had my diff fluid changed a couple of weeks ago. Just a maintenance change due to road racing....there were no issues or leaks.
Now I noticed a little leaking at the drainplug. And a little grinding on my first sharp turn in the morning when fluid is cold.
I watched the guy change the fluid and before I could stop him he placed the additive first, then the gear oil. GM fluids were used.
Is it possible that the additive is not completely mixed after several hundred miles....sitting in the bottom recesses of the diff. And that it is slowly seeping past the drain plug gasket.
Thanks
DH
Now I noticed a little leaking at the drainplug. And a little grinding on my first sharp turn in the morning when fluid is cold.
I watched the guy change the fluid and before I could stop him he placed the additive first, then the gear oil. GM fluids were used.
Is it possible that the additive is not completely mixed after several hundred miles....sitting in the bottom recesses of the diff. And that it is slowly seeping past the drain plug gasket.
Thanks
DH
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Seems plausible in initial fill, not sure what the specific gravity of each is but once it heats up I would think it would mix. Also, when I re-install the drain I usually screw it part way in and then wipe under the seal so I don't tray any oil that could drip later. Not sure how much is coming out, but if it was just a drop or two that may be why as well.
Pro
Joined: Feb 2005
Posts: 725
Likes: 89
From: East Northport NY
can't wait to see the answer from someone who knows. I remember reading somewhere in here about doing a bunch of "figure-eights" to get it all mixed properly. I'm starting to hear some weird noises coming from ( I think) the rear on a slow sharp right turn...a groaning of some sort.
Melting Slicks
Joined: Jul 2004
Posts: 2,507
Likes: 0
From: Wilmington Ca.
Howie!Howie! Your technician probably put the additive in first so he could just add gear oil to the full mark. Just easier than trying to leave room to add it after the gear oil. I think the additive is well mixed with the gear oil by now. 
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
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From: SoCal
GM Synthetic and Additive were used.
Figure 8's were done.
I know in the past one quart of oil was placed first then the additive and then the 2nd quart.......FRANK....the diff holds it all ..... no measurement !!!!!!
I don't hear anything after that first sharp, slow turn in the morning.
DH
Figure 8's were done.
I know in the past one quart of oil was placed first then the additive and then the 2nd quart.......FRANK....the diff holds it all ..... no measurement !!!!!!
I don't hear anything after that first sharp, slow turn in the morning.
DH
Melting Slicks
Joined: Jul 2004
Posts: 2,507
Likes: 0
From: Wilmington Ca.
GM Synthetic and Additive were used.
Figure 8's were done.
I know in the past one quart of oil was placed first then the additive and then the 2nd quart.......FRANK....the diff holds it all ..... no measurement !!!!!!
I don't hear anything after that first sharp, slow turn in the morning.
DH
Figure 8's were done.
I know in the past one quart of oil was placed first then the additive and then the 2nd quart.......FRANK....the diff holds it all ..... no measurement !!!!!!
I don't hear anything after that first sharp, slow turn in the morning.
DH
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Thread Starter
Team Owner
Joined: May 2004
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From: SoCal
Safety Car
Joined: Jul 2005
Posts: 4,275
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From: Vancouver WA
The differential is suppose to only hold 1.69 quarts of oil. Not 2 quarts. And 4 oz. of the additive. Some oils has the additive already mixed in with it.
Are you sure it's not overfilled?
You can could go and get 2 quarts of Amsoil or Royal purple for $20-$25 and do it yourself. Do the figure 8s, and if it doesn't chatter, then you won't need to add the additive. Amsoil and RP already as the additive in it. If it chatters, then you will need to add a little. Just don't put in too much additive.
Are you sure it's not overfilled?
You can could go and get 2 quarts of Amsoil or Royal purple for $20-$25 and do it yourself. Do the figure 8s, and if it doesn't chatter, then you won't need to add the additive. Amsoil and RP already as the additive in it. If it chatters, then you will need to add a little. Just don't put in too much additive.
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
Likes: 232
From: SoCal
The differential is suppose to only hold 1.69 quarts of oil. Not 2 quarts. And 4 oz. of the additive. Some oils has the additive already mixed in with it.
Are you sure it's not overfilled?
You can could go and get 2 quarts of Amsoil or Royal purple for $20-$25 and do it yourself. Do the figure 8s, and if it doesn't chatter, then you won't need to add the additive. Amsoil and RP already as the additive in it. If it chatters, then you will need to add a little. Just don't put in too much additive.
Are you sure it's not overfilled?
You can could go and get 2 quarts of Amsoil or Royal purple for $20-$25 and do it yourself. Do the figure 8s, and if it doesn't chatter, then you won't need to add the additive. Amsoil and RP already as the additive in it. If it chatters, then you will need to add a little. Just don't put in too much additive.
But that seems unlikey. It was filled on a level surface. How can you overfill if the fill hole is on the side of the differential .... not on the top????
DH
Le Mans Master
Joined: Mar 2002
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From: PNW
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
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From: SoCal
Well it WAS over filled......I let it drain till it stoped. And the whole underside was coated in oil....so it must have been WAY overfilled.
I will see if it stops leaking. I hope everything went out the overfill hole and that the side plate seals were not affected......I have already had that fixed twice.
I hope the little bit of groaning/grinding I am gettting on sharp turns is that I need to add a little more of the Additive as it was TOO diluted obviously......
DH
I will see if it stops leaking. I hope everything went out the overfill hole and that the side plate seals were not affected......I have already had that fixed twice.
I hope the little bit of groaning/grinding I am gettting on sharp turns is that I need to add a little more of the Additive as it was TOO diluted obviously......
DH
Burning Brakes
Joined: Apr 2005
Posts: 1,123
Likes: 14
From: Booker Texas
Mine was blowing out the vent on top.Pulled fill plug and let it drain over night and next morning installed plug and washed.Not a drop and still clean after 2 years.Hope that fixes yours!
Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
From a performance standpoint, the amount of additive is critical. Too little and it will chatter and too much and you will lose the limited slip ability. Sounds like a drain and do over to me to ensure the correct ratio.
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
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From: SoCal
Still had some drip marks after driving it even though I drained the overflll from the fill plug and cleaned up the oil drips/splatter.
I hope it is just some excess in nooks and crannies I could not reach or the drain washer.......otherwise my the top vent my be stuck
I gotta get under there again and look.....
DH
Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
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From: SoCal
Well again today there was more leakage. Dripping down the rear crossmember. I'm freakin out over this.
Maybe the vent hole is stuck open.
Maybe the excess blew the side plate seal.
This sucks..........
DH
Maybe the vent hole is stuck open.
Maybe the excess blew the side plate seal.
This sucks..........
DH
Premium Supporting Vendor
Joined: Aug 2001
Posts: 5,364
Likes: 38
From: King George VA
DH,
Leakage from the rear diff of C5s is very common and usually from these sources:
- Vent plug on top driver's side of diff. This vent is designed to vent overpressure. I've experienced some loss of fluid out this vent when the diff is very hot, such as on the track. I believe the failure of this part is rare.
- Leakage past fill plug. I can't seem to get my fill plug to seal. I fill to the fill plug, but believe the fluid expands somewhat when its hot causing the level to rise over the fill plug and then I get weepage. This is a minor inconvenience. I usually just remove the fill plug, let some drain out, then close it.
- The worst, and most common is a leaking axle seal - driver's side is by far the most common. As the vent is on the same side, it is easy to confuse the two. If you have a bunch of fluid on the driver's side and not the passenger side, I'd suspect driver's side axle seal leakage. There are many TSBs out on this.
FYI, I've been using this diff fluid for years without any additive as it already as additive pre-mixed in:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
Leakage from the rear diff of C5s is very common and usually from these sources:
- Vent plug on top driver's side of diff. This vent is designed to vent overpressure. I've experienced some loss of fluid out this vent when the diff is very hot, such as on the track. I believe the failure of this part is rare.
- Leakage past fill plug. I can't seem to get my fill plug to seal. I fill to the fill plug, but believe the fluid expands somewhat when its hot causing the level to rise over the fill plug and then I get weepage. This is a minor inconvenience. I usually just remove the fill plug, let some drain out, then close it.
- The worst, and most common is a leaking axle seal - driver's side is by far the most common. As the vent is on the same side, it is easy to confuse the two. If you have a bunch of fluid on the driver's side and not the passenger side, I'd suspect driver's side axle seal leakage. There are many TSBs out on this.
FYI, I've been using this diff fluid for years without any additive as it already as additive pre-mixed in:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
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Thread Starter
Team Owner
Joined: May 2004
Posts: 26,345
Likes: 232
From: SoCal
DH,
Leakage from the rear diff of C5s is very common and usually from these sources:
- Vent plug on top driver's side of diff. This vent is designed to vent overpressure. I've experienced some loss of fluid out this vent when the diff is very hot, such as on the track. I believe the failure of this part is rare.
- Leakage past fill plug. I can't seem to get my fill plug to seal. I fill to the fill plug, but believe the fluid expands somewhat when its hot causing the level to rise over the fill plug and then I get weepage. This is a minor inconvenience. I usually just remove the fill plug, let some drain out, then close it.
- The worst, and most common is a leaking axle seal - driver's side is by far the most common. As the vent is on the same side, it is easy to confuse the two. If you have a bunch of fluid on the driver's side and not the passenger side, I'd suspect driver's side axle seal leakage. There are many TSBs out on this.
FYI, I've been using this diff fluid for years without any additive as it already as additive pre-mixed in:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
Leakage from the rear diff of C5s is very common and usually from these sources:
- Vent plug on top driver's side of diff. This vent is designed to vent overpressure. I've experienced some loss of fluid out this vent when the diff is very hot, such as on the track. I believe the failure of this part is rare.
- Leakage past fill plug. I can't seem to get my fill plug to seal. I fill to the fill plug, but believe the fluid expands somewhat when its hot causing the level to rise over the fill plug and then I get weepage. This is a minor inconvenience. I usually just remove the fill plug, let some drain out, then close it.
- The worst, and most common is a leaking axle seal - driver's side is by far the most common. As the vent is on the same side, it is easy to confuse the two. If you have a bunch of fluid on the driver's side and not the passenger side, I'd suspect driver's side axle seal leakage. There are many TSBs out on this.
FYI, I've been using this diff fluid for years without any additive as it already as additive pre-mixed in:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
Nice to hear from you. I had absolutely no leakage since my last driver plate seal job by GM a year ago. Then this mess started after me trying to do proper maintanence since I track it.
Do you think it being a little over filled ..... at most .3 qt since he managed to get most of the two 1 qt bottles could blow the seals ????????? Or cuase the vent to stick open?????
DH