What is this rubber hanger of my rear shackles

Hello ‘Dogs’ and welcome to the forum. Oh very cool, you’ve got those. I’m not 100% but I think those are dampers to iron out certain vibration frequencies in the rear springs.

I saw something similar when looking at a Hiace on the Cars and Bids website that’s run by Doug Demuro. He has a big YouTube following and started (there) reviewing unusual cars; those with ‘quirks and features’.

The position of those dampers is quite unusual, to me. I have a leaf sprung Hiace and the similar dampers are bolted to a flanged portion of one of the leaves of the spring and are situated on the portion of the spring ahead of the axle. Take a look at PNC#48370 here (my van):
https://toyota.epc-data.com/regius_ace/lh119v/114894/chassis/4804/

It makes a bit more sense to me to have the damper on the spring itself rather than the shackle (which might also impact on clearance) but I think that’s what they are. They seem to be the same family of parts, but I’ve not seen the type you have on the EPC.

The damper itself is actually quite heavy. Adding a bit of mass is a common way to damp vibration (like sound deadening a panel). Years ago there was a fad to glue a small weight to the tip of skis to stop them wobbling. Somewhat counter-intuitive but there you go.

By the way I’m impressed how clean and tidy the underneath of your van is!

HTH

Thanks for the reply
I thought initially they may be to tie down the vehicle for security reasons when parked in Japan as they are mainly parked in car parks or to secure the van when transporting. Everyone I asked didn’t know

They probably are for something like vibrations but that's a bit boring... Much better if they're wheelie bars for when it used to be a drag racer.