Hey guys first time poster here!

i bought a 500 dollar 1969 mercedes diesel with a 4 speed manual!(runs great minor blowby but shes a TOTAL rustbucket! ) a year ago and i've been driving daily woo!

i've been hearing a deceleration noise coming from the rear.. it was intermittent before.. But it's every time i slowdown or brake.. if i aggressively downshift its quite a howl! .. My flexdisc looks ok no clunking or roughness.. Dif is full of fluid..

Not sure what to check next..