I have a volvo VNM 630 2012 with 564000 miles, is showing RETARDER TEMPERATURE HIGH anyone know it

Check the oil level in the transmission, it could be low causing high temperatures.

 

And check your oil pressure as well in both engine and transmission. If they agree along with your axles you are ok. Something is going on. Im inclined to follow Boneebone here for sure.

In my day we use Jacobs over the Pistons the hard way. Never had em fail unless the fuse box got loose somehow.

In the meantime turn off the retarder and get to a shop where you can safely check the oil levels.

 

The only retarder that can get hot is the euro electric eddy retarders. They dump the heat in heatsinks. Otherwise it wouldn't make sense to me why it would warn of that.

Retarder (mechanical engineering) - Wikipedia

 

What engine is in your truck and the transmission ??? Do you have error codes??

 

It looks like it's an electric retarder in the transmission. Could be a dirty heatsink, clogged oil cooler, or something of that sort. It could just be that you're using it too much for it's specifications.

Could just be a simple hydraulic retarder.

 

Would it be possible you have a factory installed pto Set up and have left it on not knowing. and thats why its calling retarder temp high.