diff side play? replies needed quick!

[lewis666]

hi there,

i was fitting my steel idler gear kit when i noticed my rear diff has a huge amount of play from side to side?

it was not like this when i got the car but i gave the diffs a rebuild the day after my first meeting with the car and it has no play on the diffs at the race meeting. what could be causing this problem?

i need some help quick because i should be racing it tomorrow.

many thanks

lewis