clunking gearbox

[choppermark]

my vt v6 auto drives fine, but last night noticed, when slowing down there was a massive clunk, going back into first gear, so took off again , gears change smoothly, then again , slow down & the gearbox clunks again. what is the cause of this? is it to do with a linkage or somthing? have checked the oil, did have to top it up , but still clunking back into first gear from stand still.
cheers, any help would be appreciated

[som]

i had something similar some time ago, park to first ,park to reverse.i serviced my auto including completely changing the fluid in the torque converter and all was fixed.i only changed the fluid in the torque converter because my mechanic,in his wisdom,had added some "conditioner"on a previous service and i wanted to make sure that that was all removed.hope this helps.

[1_johnboy]

almost sounds like "lash" in the diff