Differential Question
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
Likes: 10
From: Aiken SC
Differential Question
Looking for some help.
I bought a C5Z from a friend as a project CAM-S car for SCCA Autocross.
The car has Heads, Cam, Intake , and lots of other mods by previous owners, I have receipts and history for some of the work but not all.
Just trying to catalog a baseline with that car, I was going to perform a break-away test on the rear end to see if the diff was still good.
I followed Froggys guide on Youtube, and could not get the wheel that was in the air to breakaway even 200lb-ft + of applicaiton. I Decided I did not want to put anymore load on the diff.
I tried both passenger and drivers rear wheels, making sure I was in-gear, with parking break off.
This got me thinking, I wonder if this car does not have a factory diff?
Sharp circles in a parking not have no issues, and both tires hook up on hard launches.
Any idea of how to confirm what LSD I have without cracking the casing open??
Thanks for any guidance on this.
I bought a C5Z from a friend as a project CAM-S car for SCCA Autocross.
The car has Heads, Cam, Intake , and lots of other mods by previous owners, I have receipts and history for some of the work but not all.
Just trying to catalog a baseline with that car, I was going to perform a break-away test on the rear end to see if the diff was still good.
I followed Froggys guide on Youtube, and could not get the wheel that was in the air to breakaway even 200lb-ft + of applicaiton. I Decided I did not want to put anymore load on the diff.
I tried both passenger and drivers rear wheels, making sure I was in-gear, with parking break off.
This got me thinking, I wonder if this car does not have a factory diff?
Sharp circles in a parking not have no issues, and both tires hook up on hard launches.
Any idea of how to confirm what LSD I have without cracking the casing open??
Thanks for any guidance on this.
AMP Racing
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2023 C5 of the Year Finalist - Modified
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You’ll have to open the case to determine if it’s been changed. Might be just a rebuilt with factory clutch packs, or an Eaton piece. Either way, I don’t think I’d sweat it at all... Seems like it’s good to go for your setup.
Le Mans Master
Joined: Jul 2010
Posts: 6,013
Likes: 726
Looking for some help.
I bought a C5Z from a friend as a project CAM-S car for SCCA Autocross.
The car has Heads, Cam, Intake , and lots of other mods by previous owners, I have receipts and history for some of the work but not all.
Just trying to catalog a baseline with that car, I was going to perform a break-away test on the rear end to see if the diff was still good.
I followed Froggys guide on Youtube, and could not get the wheel that was in the air to breakaway even 200lb-ft + of applicaiton. I Decided I did not want to put anymore load on the diff.
I tried both passenger and drivers rear wheels, making sure I was in-gear, with parking break off.
This got me thinking, I wonder if this car does not have a factory diff?
Sharp circles in a parking not have no issues, and both tires hook up on hard launches.
Any idea of how to confirm what LSD I have without cracking the casing open??
Thanks for any guidance on this.
I bought a C5Z from a friend as a project CAM-S car for SCCA Autocross.
The car has Heads, Cam, Intake , and lots of other mods by previous owners, I have receipts and history for some of the work but not all.
Just trying to catalog a baseline with that car, I was going to perform a break-away test on the rear end to see if the diff was still good.
I followed Froggys guide on Youtube, and could not get the wheel that was in the air to breakaway even 200lb-ft + of applicaiton. I Decided I did not want to put anymore load on the diff.
I tried both passenger and drivers rear wheels, making sure I was in-gear, with parking break off.
This got me thinking, I wonder if this car does not have a factory diff?
Sharp circles in a parking not have no issues, and both tires hook up on hard launches.
Any idea of how to confirm what LSD I have without cracking the casing open??
Thanks for any guidance on this.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
Likes: 10
From: Aiken SC
Following the Froggy method, pretty common way of testing clutchpack LSD, I could not get the wheel that is in the air to rotate. After I maxed out my torque wrench I put a breaker bar on and turned as hard as I dared and nothing.
I am not worried about it being broken since it seems to operate as it should, I am just more curious as to whats in there for reference when I am testing and setting up the car.
Thanks!
I am not worried about it being broken since it seems to operate as it should, I am just more curious as to whats in there for reference when I am testing and setting up the car.
Thanks!
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
Take it out of gear, and try. That's the proper way to test breakaway torque. Otherwise you're fighting engine compression.
FYI, supposedly when refreshed, the LSD should be somewhere in the neighborhood of 100-150 ft-lbs breakaway torque. If your not-newly-refreshed LSD is exceeding that then either there's something wrong with it, or the test method.
FYI, supposedly when refreshed, the LSD should be somewhere in the neighborhood of 100-150 ft-lbs breakaway torque. If your not-newly-refreshed LSD is exceeding that then either there's something wrong with it, or the test method.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
Likes: 10
From: Aiken SC
Take it out of gear, and try. That's the proper way to test breakaway torque. Otherwise you're fighting engine compression.
FYI, supposedly when refreshed, the LSD should be somewhere in the neighborhood of 100-150 ft-lbs breakaway torque. If your not-newly-refreshed LSD is exceeding that then either there's something wrong with it, or the test method.
FYI, supposedly when refreshed, the LSD should be somewhere in the neighborhood of 100-150 ft-lbs breakaway torque. If your not-newly-refreshed LSD is exceeding that then either there's something wrong with it, or the test method.
This is the proceedure I followed.
Le Mans Master
Joined: Jul 2010
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Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
And the clutch packs were TOAST:
I did a rebuild of the LSD using C6 Z06 clutch packs and belleville springs.
Just because it's on the internet, doesn't mean it's right
Think about it: if you have one drive wheel on the ground, trans in gear, and you're turning the free wheel, you're spinning the trans and the engine as well. So you're not succeeding to turn it because you're fighting engine compression. If you put the trans in a higher gear I bet you'd find less resistance to spinning the wheel.
Last edited by MetalMan2; Sep 17, 2021 at 01:17 PM.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
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From: Aiken SC
Maybe I am thinking about this wrong . . . But with the trans in Neutral, and one wheel in the air, wouldnt i be able to turn the wheel in the air freely with or without the LSD being faulty? I would just be spinning the trans and torque tube at that point in time? I guess i need to pull the diff out and take a look see. . .
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
Maybe I am thinking about this wrong . . . But with the trans in Neutral, and one wheel in the air, wouldnt i be able to turn the wheel in the air freely with or without the LSD being faulty? I would just be spinning the trans and torque tube at that point in time? I guess i need to pull the diff out and take a look see. . .
The LSD puts a load against the clutch packs (friction disks), so spinning one wheel against the other will have resistance with or without trans in gear.
FWIW: if you lift up the whole rear of the car and put the trans in gear, if your LSD has failed then when you spin one wheel the other wheel will spin the opposite and without resistance.
Yes:
- 2x C6 Z06 clutch packs: GM 19132906 (they are sold as 1 each)
- 2x C6 Z06 belleville springs: GM 19132817 (they are sold as 1 each)
- 2x side cover O-rings GM 89047953 (they are sold as 1 each)
- 2x output shaft seals GM 88996703 (they are sold as 1 each)
Last edited by MetalMan2; Aug 17, 2020 at 11:08 AM.
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
If I can remember, later today I'll see about putting up a rear corner of my Z06, with trans in neutral, and test breakaway torque on the rebuilt LSD that will have about 80 miles on it.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
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From: Aiken SC
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
Okay, I was able to make 5 minutes to check it out.
Driver-rear wheel off the ground, e-brake off, trans in neutral.
Torque wrench on a lug nut, oriented to mimic torque being applied to the axle nut.
Started at 60 ft-lbs and worked my way up to 100 ft-lbs. The wheel never slipped even at 100 ft-lbs. I didn't go any higher because that's the limit for the lug nuts.
Keep in mind this same test, pre-LSD-rebuild, the wheel spun freely.
Driver-rear wheel off the ground, e-brake off, trans in neutral.
Torque wrench on a lug nut, oriented to mimic torque being applied to the axle nut.
Started at 60 ft-lbs and worked my way up to 100 ft-lbs. The wheel never slipped even at 100 ft-lbs. I didn't go any higher because that's the limit for the lug nuts.
Keep in mind this same test, pre-LSD-rebuild, the wheel spun freely.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
Likes: 10
From: Aiken SC
Okay, I was able to make 5 minutes to check it out.
Driver-rear wheel off the ground, e-brake off, trans in neutral.
Torque wrench on a lug nut, oriented to mimic torque being applied to the axle nut.
Started at 60 ft-lbs and worked my way up to 100 ft-lbs. The wheel never slipped even at 100 ft-lbs. I didn't go any higher because that's the limit for the lug nuts.
Keep in mind this same test, pre-LSD-rebuild, the wheel spun freely.
Driver-rear wheel off the ground, e-brake off, trans in neutral.
Torque wrench on a lug nut, oriented to mimic torque being applied to the axle nut.
Started at 60 ft-lbs and worked my way up to 100 ft-lbs. The wheel never slipped even at 100 ft-lbs. I didn't go any higher because that's the limit for the lug nuts.
Keep in mind this same test, pre-LSD-rebuild, the wheel spun freely.
Melting Slicks
Joined: Dec 2018
Posts: 2,663
Likes: 1,389
From: Orange County, CA
I had bought the side gear compressor tool (to be used with a press), which is Kent Moore J-42162. My old belleville springs were so bad that the tool was unnecessary to disassemble the diff. But it's definitely needed for reassembly. I'd be happy to lend or sell my tool if you're interested... with any luck I shouldn't need it for a long time.
Thread Starter
Instructor
Joined: Nov 2017
Posts: 155
Likes: 10
From: Aiken SC
I had bought the side gear compressor tool (to be used with a press), which is Kent Moore J-42162. My old belleville springs were so bad that the tool was unnecessary to disassemble the diff. But it's definitely needed for reassembly. I'd be happy to lend or sell my tool if you're interested... with any luck I shouldn't need it for a long time.