Differential Wear via Used Oil Analysis
02-04-2014, 05:20 PM
#11
I have used a 50/50 mix of M1 75/90 and 75/140 in my trucks and cars(with rear wheel drive) and my S. I've used this mix for over 30 years with out a rear end failure(due to the lube). I put 25k to 30k miles a year on the S, so I change it once a year. 103k miles and climbing
ROD
ROD
02-07-2014, 09:45 AM
#13
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Accelerated differential wear on an OE diff happens when the preload crush sleeve (the one that puddymod replaces) deforms. This changes the interface between the ring gear and pinion. The only way to slow down wear is to not launch the car with a clutch drop, or to replace the crush sleeve with a tube, like on the puddymod diff. The only way the puddy mod is legal is if you're racing in a class that allows it or if you just want a really strong, really durable differential. While a gear oil with a higher pressure film strength will decrease the wear because it should remain in place between the two gear surfaces, you are still continuously "breaking" in the the diff as every change in the geometry of the preload sleeve/pinion/ring gear requires the surfaces to re-mesh.
It's just math.
It's just math.
02-07-2014, 10:53 AM
#14
Accelerated differential wear on an OE diff happens when the preload crush sleeve (the one that puddymod replaces) deforms. This changes the interface between the ring gear and pinion. The only way to slow down wear is to not launch the car with a clutch drop, or to replace the crush sleeve with a tube, like on the puddymod diff. The only way the puddy mod is legal is if you're racing in a class that allows it or if you just want a really strong, really durable differential. While a gear oil with a higher pressure film strength will decrease the wear because it should remain in place between the two gear surfaces, you are still continuously "breaking" in the the diff as every change in the geometry of the preload sleeve/pinion/ring gear requires the surfaces to re-mesh.
It's just math.
It's just math.
More for my daily drive s2000s that I never launch on. I know its kind of irrelevant the R&C topic. All i care about in the race car is a good anti-"shock" fluid and minimal heat. These get rebuild annually.
-Marc
02-11-2014, 11:00 AM
#15
Thread Starter
I e-mailed Amsoil about the reports asking for advice and got this in return...
Hi Chris,
My name is Allen Bender and your inquiry was forwarded to me because I am the oil analysis manager. Thank you for sending in your Blackstone lab reports for us to review. I have reviewed many Blackstone lab reports over the years and have found their test results to be accurate, but I don’t always agree with their interpretation of the numbers.
First, the transmission fluid. I agree that Lead is on the high side of the normal range, but the Copper level is fine. Autocrossing is going to put more stress on the bearings than normal driving, so seeing more bearing wear metals is to be expected.
Second, the differential fluid. I agree that the most recent test results are significantly higher than the previous sample and that a higher rate of wear is occurring. That said, the numbers themselves are not as bad as they look. Of the metals mentioned, only Nickel would be flagged as abnormally high by the wear metals standards we use. Your primary question, however, is if there is a better product that will provide more protection and the answer to that is yes. Under the severe service conditions you are driving under, I would recommend increasing the viscosity to 75W-110(side note: this is the viscosity I've been using, not 75w-90). Although AMSOIL offers higher-viscosity gear lubes, you want to use the lightest viscosity that provides adequate protection since it will take less horsepower and run cooler than a heavier-viscosity product. You could always move up to a 75W-140 later if you choose.
Third, your engine oil. The wear metals are low, very low in light of how the vehicle is used. Don’t change anything here.
Other than trying a higher-viscosity gear lube, I don’t see a need for other changes. Autocrossing will likely show higher levels of wear than normal driving regardless of what products are used, but the viscosity change may help with that.
Sincerely,
Allen Bender, MLA II
Manager
Hi Chris,
My name is Allen Bender and your inquiry was forwarded to me because I am the oil analysis manager. Thank you for sending in your Blackstone lab reports for us to review. I have reviewed many Blackstone lab reports over the years and have found their test results to be accurate, but I don’t always agree with their interpretation of the numbers.
First, the transmission fluid. I agree that Lead is on the high side of the normal range, but the Copper level is fine. Autocrossing is going to put more stress on the bearings than normal driving, so seeing more bearing wear metals is to be expected.
Second, the differential fluid. I agree that the most recent test results are significantly higher than the previous sample and that a higher rate of wear is occurring. That said, the numbers themselves are not as bad as they look. Of the metals mentioned, only Nickel would be flagged as abnormally high by the wear metals standards we use. Your primary question, however, is if there is a better product that will provide more protection and the answer to that is yes. Under the severe service conditions you are driving under, I would recommend increasing the viscosity to 75W-110(side note: this is the viscosity I've been using, not 75w-90). Although AMSOIL offers higher-viscosity gear lubes, you want to use the lightest viscosity that provides adequate protection since it will take less horsepower and run cooler than a heavier-viscosity product. You could always move up to a 75W-140 later if you choose.
Third, your engine oil. The wear metals are low, very low in light of how the vehicle is used. Don’t change anything here.
Other than trying a higher-viscosity gear lube, I don’t see a need for other changes. Autocrossing will likely show higher levels of wear than normal driving regardless of what products are used, but the viscosity change may help with that.
Sincerely,
Allen Bender, MLA II
Manager
02-12-2014, 12:51 AM
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I have looked at a few S2K diff samples under the microscope.
Some stuff on my AP1 from last year
oil analysis
Some stuff on my AP1 from last year
oil analysis
02-15-2014, 08:09 AM
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The checking distance (CD) is set with shimms between the main pinion bearing and the pinion head and this does not change under load.
What does change the CD is flexing bearing caps, IOW when the ring is pushed backwards by the pinion.
This happens when the friction between pinion and ring is high enough so the turning pinion does not turn the ring put pushes it away at the pressure angle.
Its (relatively) simple mechanics......
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