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Old 03-04-2022, 12:08 AM   #1
cmitchell17

 
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How many people have had stock SS (2.77) Differential Failures?

I have heard of others having failures and they had slight mods as well. I think mine is having issues as well, right before I was about to drive it almost 1000 mile trip it starts making noise. I guess its better now than 500 miles away from home.

I randomly started noticing a pretty faint whirling noise, so I pulled the rear seat down to listen to it more. The whirr noise changes significantly as the driveline is loaded and unloaded while coasting. I put a chassis ear microphone on the brake caliper and subframe for controls then put one on the differential housing. After driving it around the noise coming from the differential is significantly louder than both the caliper and subframe noises so I am sure its the differential.

I have pulled out this differential from the car I think twice now, but that was because I put in a 3.73 M6 differential then couldn't make up my mind if I wanted to stay with it or not and eventually went back to my stock 2.77 differential. So the fluid has been changed at least since then which was 20-30k miles ago when I swapped them back and forth. But its the same differential that I have had for almost the entire cars life, except for the 500-1000 or so miles I drove on the 3.73 differential. I am not at 104,000 miles. About 30k of that has been with a cam and ported heads. I would have way thought I would have blown a weak driveshaft by now before a rear end.

I also noticed when the car is jacked up off the ground and you shake the tire back and forth and watch the inner CV joints that go into the differential, they seem to have a little play in and out a slight amount, I would assume this is maybe from the LSD?

From a search it looks like this may be more common than I thought. Here is one that seems similar:
https://www.camaro6.com/forums/showt...erential+noise
But they ended up saying it was a wheel bearing, but I am almost certain a wheel bearing noise would not change when letting on and off the throttle?

The noise, at least with the back seat up, is really only noticeable once you get up to say 30 or 40 mph. You cannot hear anything at low speed or when during sharp turns. I think the noise gets a little louder when you let off the gas and the car is coasting.

The noise doesn't seem to come at a certain speed then go away once above a certain speed, like a bearing preload issue or something like that. It more seems to gradually get louder as speed gets higher up to about 50 or 60 then kind of stays the same loudness.

Also pointed a laser thermometer at it with the emissivity set at 0.80 and it read around 110 F, so I don't think anything is getting hot or overheated.

Last edited by cmitchell17; 03-04-2022 at 12:48 AM.
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Old 03-05-2022, 08:07 PM   #2
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There was at least one differential failure at the Cadillac Attack, but the OEM unit is not designed for the additional power being applied
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Old 03-05-2022, 08:53 PM   #3
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Quote:
Originally Posted by cmitchell17 View Post
I have heard of others having failures and they had slight mods as well. I think mine is having issues as well, right before I was about to drive it almost 1000 mile trip it starts making noise. I guess its better now than 500 miles away from home.

I randomly started noticing a pretty faint whirling noise, so I pulled the rear seat down to listen to it more. The whirr noise changes significantly as the driveline is loaded and unloaded while coasting. I put a chassis ear microphone on the brake caliper and subframe for controls then put one on the differential housing. After driving it around the noise coming from the differential is significantly louder than both the caliper and subframe noises so I am sure its the differential.

I have pulled out this differential from the car I think twice now, but that was because I put in a 3.73 M6 differential then couldn't make up my mind if I wanted to stay with it or not and eventually went back to my stock 2.77 differential. So the fluid has been changed at least since then which was 20-30k miles ago when I swapped them back and forth. But its the same differential that I have had for almost the entire cars life, except for the 500-1000 or so miles I drove on the 3.73 differential. I am not at 104,000 miles. About 30k of that has been with a cam and ported heads. I would have way thought I would have blown a weak driveshaft by now before a rear end.

I also noticed when the car is jacked up off the ground and you shake the tire back and forth and watch the inner CV joints that go into the differential, they seem to have a little play in and out a slight amount, I would assume this is maybe from the LSD?

From a search it looks like this may be more common than I thought. Here is one that seems similar:
https://www.camaro6.com/forums/showt...erential+noise
But they ended up saying it was a wheel bearing, but I am almost certain a wheel bearing noise would not change when letting on and off the throttle?

The noise, at least with the back seat up, is really only noticeable once you get up to say 30 or 40 mph. You cannot hear anything at low speed or when during sharp turns. I think the noise gets a little louder when you let off the gas and the car is coasting.

The noise doesn't seem to come at a certain speed then go away once above a certain speed, like a bearing preload issue or something like that. It more seems to gradually get louder as speed gets higher up to about 50 or 60 then kind of stays the same loudness.

Also pointed a laser thermometer at it with the emissivity set at 0.80 and it read around 110 F, so I don't think anything is getting hot or overheated.
Have you checked to see if the fluid is contaminated? That surely would indicate something in the differential isn’t right.
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Originally Posted by arpad_m - “Aww, yet another oil thread with almost the same question in the OP“
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Old 03-06-2022, 08:58 PM   #4
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Originally Posted by Trochoidal View Post
Have you checked to see if the fluid is contaminated? That surely would indicate something in the differential isn’t right.
Hopefully I can drain it tomorrow and look at it. I just got back home and took it for about a 15 or so mile round trip. The noise is still barely noticeable, I would probably be the only one that could notice it.
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Old 03-06-2022, 09:09 PM   #5
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Quote:
Originally Posted by JSH View Post
There was at least one differential failure at the Cadillac Attack, but the OEM unit is not designed for the additional power being applied
I agree 100% the unit is only designed for stock power levels, I would just hope they, as they usually do, would design in a pretty significant safety factor. I don't know what automotive design usually targets but I think I have seen 2.0-2.5 number thrown around but I think that was more for internal engine components. But that number seems plausible as it seems like people see failure starting at about double the power output (safety factor of 2) and start really pushing their luck at about 2.5 in mostly forced induction applications.

I've always been really curious about this, but I doubt you could ever find out GM's internal durability design standards and safety factors they shoot for given that its internal GM confidential engineering info.

In this case it seems less of a hard part failure or breakage from overstress but more like a bad bearing or something. A search of the forums gives mostly results only about the groan thing, which I had a few times new then went away. I can't find anything in the warranty subforums about bearing issues. However, I do see some things about wheel bearings, but hooking up the microphone I should hear a louder noise from hooking to the spindle than hooking to the differential. And the noise is way way louder hooking it to the diff.
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Old 03-13-2022, 02:32 PM   #6
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Can anyone confirm the GM part number for the 2.77 auto SS differential? So I think it might be 84637769, but then there is also 84080680 but GM didn't put any description by that part number besides "F Carrier". The 84637769 says SS, auto trans, but then it says excluding oil cooler, and I am pretty sure all SS's came with oil coolers so this is pretty confusing.

I was wanting to find a V6 3.27 manual differential so I could go to higher gears, I tried the SS manual differential (which I think the PN for that one was either 84080682 or maybe 255095523) but it was too low of a gear for me so I swapped back to my original one and sold that one. So now I am just thinking about trying to buy another stock one and pulling mine apart and trying to fix it.
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Old 03-13-2022, 02:34 PM   #7
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Also anyone know why there is seems to be no info and no aftermarket support for these differentials? I think AAM made the 5th gen ones, then it looks like maybe all of the manufacturing and tooling got sold to Magna, and then the trail goes cold there.

I guess when you can just swap to a whole different axel conversion, no one bothers trying to make the stock integrated unit work.
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Old 03-13-2022, 08:48 PM   #8
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So I tried to get my microphone to record directly to digital audio, but I found out phones are only audio inputs on the headphone jack, so I tired my laptop but I couldn't get it to work either. So I hooked the headphones up and turned the volume all the way up and recorded with my phone so there's a little bit of noise.

I hooked the microphone clamps up to all 4 sides of the diff, one on driver's side on the nut that holds the oil cooler fitting on, one on the passenger side of cast surface, one on the front near the pinion input on cast surface, and the other on the very back of the diff on cast surface.

Unfortunately I can't really tell which one is louder. I was hoping to try to figure out if it was a pinion bearing, or driver's or passenger side axle bearing.

Since I can't really tell I guess that means it might be the differential gears. To me it doesn't sound like a gear whine, but more like a grinding bearing sound. But the fact that it makes a completely different sound when you are on the gas versus coasting makes me think its a gear as well. I would think a bearing would make a constant noise weather on or off the gas, maybe a pinion bearing might change pitch a little but this is a completely different sound when on and off the gas.

I recorded one with just my phone inside the cab with no microphone hooked up but you couldn't really hear anything.

I also read through the service manual, apparently the only thing GM thinks is serviceable on these diffs are the seals, axle shafts, and gaskets. So they expect you to buy a whole new diff for everything else I guess.

Diff noises from 4 different locations around diff.zip
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Old 07-29-2022, 09:27 AM   #9
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Bring back because mine just failed at 97,000. Basically stock car other than a tune and cat back exhaust. Taken to the drag strip 2 times and I think that is what killed it because of the bad wheel hop a few times. Not going to complain about it other than the only fix is to buy a new rear diff for $1600. waiting for the dealership to confirm the failure and that they have odered the diff.https://www.gmpartsdirect.com/oem-pa...bC12OC1nYXM%3D
This is for 1SS A8 Coupe thae part numbers are very specific as they are different for Convertable and Coupe.
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Old 07-30-2022, 06:28 PM   #10
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I would imagine this unit would be as strong or stronger than the lsd 3.73. I had a ton of passes on the blue car and it didn’t even hum.

My s197 hummed after a handful of prepped launches, that was supposed to be a strong rear. I do not EVER power through wheel hop tho. always lift no mattter what

Interested in your rear oil change schedules and if your car gets wheel hop. Surprised to hear of ANY issues on a NA auto, even from a drag car
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Old 08-01-2022, 10:50 AM   #11
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I would imagine this unit would be as strong or stronger than the lsd 3.73. I had a ton of passes on the blue car and it didn’t even hum.

My s197 hummed after a handful of prepped launches, that was supposed to be a strong rear. I do not EVER power through wheel hop tho. always lift no mattter what

Interested in your rear oil change schedules and if your car gets wheel hop. Surprised to hear of ANY issues on a NA auto, even from a drag car
Changed the rear diff fluid aproximatley 4 times over the past 3 years. Two times with the AC Delco fluid and then the last 2 times with the Valavoline 75W90 with the correct friction modifiers in it. The first time I changed it there were substantial metal flakes on the drain plug.
So if I did something wrong it is on me and I am paying for it. Lesson learned and I know next time. Found out it also needs a drivers side axel. Just miss my car and want her back.
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Old 08-06-2022, 11:45 PM   #12
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I couldn't say out of experience, but it's my understanding the lower the ratio (i.e. 2.85 to 3.73), the more strength there, theoretically, would be in the ring and pinion gear teeth. The have near 9" ring gear, and while that doesn't guarantee strength (like a Ford 9" and all it's bearing support and all that), I thought it would be helpful.

Wasn't there a thread about swapping Grave Digger in there? You won't blow that one up, lol.
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Old 08-07-2022, 09:48 AM   #13
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Quote:
Originally Posted by dmcmahan60 View Post
Changed the rear diff fluid aproximatley 4 times over the past 3 years. Two times with the AC Delco fluid and then the last 2 times with the Valavoline 75W90 with the correct friction modifiers in it. The first time I changed it there were substantial metal flakes on the drain plug.
So if I did something wrong it is on me and I am paying for it. Lesson learned and I know next time. Found out it also needs a drivers side axel. Just miss my car and want her back.
The first fluid change always looks bad. The Valvoline fluid might be the mistake imo...AC Delco should be the only fluid used in these factory diffs. Otherwise, The Diffs are really strong with the welded ring gear which is why we can not change gears in them. Guys have been 8's with them. Axles and Driveshaft is normally all that's needed for track duty with hard launches.
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Old 08-08-2022, 09:28 AM   #14
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Update, the drivers side flange where the axel bolts to had about and 1 1/2 play in travel. So something on the inside, ie bearing was completely shot. Thanks for the replies and I will run it 500 miles and chage the fluid with AC Delco and go from there. $2600 for new rear diff, drivers side axel and labor. waiting to hear what type of warranty I have on the new parts. And to be fair this car for the first 11,000 miles of its life was an Enterprise Rental car. Thanks for the input guys. i have a video but don't know how to post.
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