Big clunk
 

My 2006 XC70 wagon has started having drivetrain issues. Began with occasional clunking sound coming from rear of car, seems like going into second gear. Happens randomly. Then it began occasionally clunking really hard and shuddering, at which point it would default to winter shift mode. If I shut off and restart car it resets back to normal. When it first did this all the gauges stopped functioning, weird. I took it to Volvo shop and had it scanned with Vadis scanner-
no transmission codes! It' is one great big mystery that I need to solve. Ideas anyone?

Are you sure it might not be an issue with the haldex unit? If your initial symptoms felt like they were coming from the rear I'd start with that. You may have a failed DEM. to my understanding it should throw a code but it's worth checking out.

Hi Swagen
I will have the Haldex unit checked and post results. Thanks for the idea!