differential windup and damage

[urq]

... another data point I did not mention earlier ... I bought an '87 5kCSQ 
once which had a "non-turbo" transmission and a "turbo" rear diff (didn't 
know that until after I bought it) ... this meant the FDRs at the front and 
rear diffs were different, so the center diff was having to differentiate at 
all times ... never had a lick of trouble with that center diff ... but it 
was a fun car to drive!  Other that the V8 this was the only quattro I've 
owned that would spin tires on pavement ....

Steve B
San Jose, CA (USA)
>
> So far the only explanation I've seen is the one that says they simply
> aren't designed to continuously accomodate differing rotational speeds
> due to lubrication and bearing issues.
>
> And "windup" is something that happens when there *isn't* a
> differential, and is either going to cause tire scrub or break an axle.
>
> I can buy into the danger and warning, relative to the fact that diffs
> just aren't designed to cope as above.  But not that there is some magic
> physics that tears an "ideal" diff apart if rolling speeds are
> different.  That part is the urban legend.
>
> The question then becomes, how much and for now long will do harm?