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HDRDTD · 02-22-2023, 01:43 AM

When the 'rattle' issued was first raised back in (i believe 2013), it was stated that the entire SC assembly was made by Eaton and was considered a 'field replaceable unit' meaning if something went wrong with any part of the SC assembly, the entire assembly was replaced and sent back to Eaton as a unit.

Back then, Eaton published a description of the rattle issue ( I wish I had kept a copy) that described the construction of the isolator and why it was made the way it was including an explanation of the purpose of the spring loaded shaft and how/why the spring would wear a grove in the shaft.
If I recall, the idea was that the gears that drive the rotors inside have a small amount of backlash, and that when the engine changes rpm, up/down, it causes a small amount of vibration.
This vibration is meant to be absorbed by the spring loaded shaft of the isolator. the shaft of the isolator was made a bit softer than the hardness of the spring to help absorption of the gear lash vibration, resulting in the groove wearing into the shaft.
Unfortunately, people objected to the sound of the rattle.
The original TSB description stated that if the rattle was heard at idle, but went away as the engine rpm increased to (i believe) 1500 rpm, then the rattle was considered normal.
If the rattle was still present as the rpm was raised, then it warranted a replacement.
The initial quick remedy was to replace the isolator with a solid one that did not include the spring.
Eaton then decided that the whole purpose of having a spring loaded isolator to absorb the gear lash vibration was still a necessary thing to insure a long life of the SC, so they went back to the spring loaded isolator but then packed it with grease to help dampen the rattle noise.

As far as I know, the SC assembly is still considered a unit as a whole GM ships them back to Eaton.

I have no idea what Eaton does with the units that are sent back.

Considering the description of the isolator and it's spring, I venture an guess that the vibration and it's issued were considered an issue to ensure a long life of the SC.

Will the SC unit begin to have issues well down the road (1,2,300.000 miles)? if it's changed to a solid isolator? I have no idea.

Yes I know many if not all speed shops will install a solid isolator and the probably wouldn't if they knew it would shorten the possible life of the SC, but who knows what the consider as an expected life of the SC. How many modded engines are used for 200,000 miles.
Again I have no idea,

In the end, all I know is that the spring was designed as part of the isolator for a reason. I simply choose to trust the engineers that designed the unit.

My sc was indeed replaced by GM under warranty back in early 2013 and has worked without any issues since then and now is at around 54,000 miles. I have no intention of ever selling the car, and yes it has seen several beginners track days.

What I have chosen to do is simply my choice.
What you choose to do is your choice.

02-22-2023, 01:43 AM	#42
HDRDTD Drives: 2013 Triple Black ZL1 Vert M6 ECF Join Date: Mar 2011 Location: Trenton, Michigan Posts: 7,046	When the 'rattle' issued was first raised back in (i believe 2013), it was stated that the entire SC assembly was made by Eaton and was considered a 'field replaceable unit' meaning if something went wrong with any part of the SC assembly, the entire assembly was replaced and sent back to Eaton as a unit. Back then, Eaton published a description of the rattle issue ( I wish I had kept a copy) that described the construction of the isolator and why it was made the way it was including an explanation of the purpose of the spring loaded shaft and how/why the spring would wear a grove in the shaft. If I recall, the idea was that the gears that drive the rotors inside have a small amount of backlash, and that when the engine changes rpm, up/down, it causes a small amount of vibration. This vibration is meant to be absorbed by the spring loaded shaft of the isolator. the shaft of the isolator was made a bit softer than the hardness of the spring to help absorption of the gear lash vibration, resulting in the groove wearing into the shaft. Unfortunately, people objected to the sound of the rattle. The original TSB description stated that if the rattle was heard at idle, but went away as the engine rpm increased to (i believe) 1500 rpm, then the rattle was considered normal. If the rattle was still present as the rpm was raised, then it warranted a replacement. The initial quick remedy was to replace the isolator with a solid one that did not include the spring. Eaton then decided that the whole purpose of having a spring loaded isolator to absorb the gear lash vibration was still a necessary thing to insure a long life of the SC, so they went back to the spring loaded isolator but then packed it with grease to help dampen the rattle noise. As far as I know, the SC assembly is still considered a unit as a whole GM ships them back to Eaton. I have no idea what Eaton does with the units that are sent back. Considering the description of the isolator and it's spring, I venture an guess that the vibration and it's issued were considered an issue to ensure a long life of the SC. Will the SC unit begin to have issues well down the road (1,2,300.000 miles)? if it's changed to a solid isolator? I have no idea. Yes I know many if not all speed shops will install a solid isolator and the probably wouldn't if they knew it would shorten the possible life of the SC, but who knows what the consider as an expected life of the SC. How many modded engines are used for 200,000 miles. Again I have no idea, In the end, all I know is that the spring was designed as part of the isolator for a reason. I simply choose to trust the engineers that designed the unit. My sc was indeed replaced by GM under warranty back in early 2013 and has worked without any issues since then and now is at around 54,000 miles. I have no intention of ever selling the car, and yes it has seen several beginners track days. What I have chosen to do is simply my choice. What you choose to do is your choice.