Technical What is this?...Ford 9 inch question

I am putting this Ford 9'' in my '40 Ford truck. Does anyone know what this yellow sleeve is and its purpose? It think it came from a '58 Galaxie, but I am not certain. I had a pile of them and I mixed a bunch up. As always, Thanks for the positive input.

 

I suspect that is for vibration control?

 

I'd guess the same. May have had some sort of rotational harmonics that the extra weight damped out.

I had a '72 Galaxie that had a weight on an arm hanging off the tailshaft of the transmission, and an '88 Lincoln with weights attached to the exhaust system. These are bandaid fixes to control some sort of vibration in the system, rather than going through the trouble of redesigning the whole system.

 

I had a couple of Fords that had weird stuff hanging in odd places, they were chasing harmonics.

 

We call them road hugging weights. But yes its to dampen some kind of vibration.