Fleet Transmissions/Dan's Auto Repair

We did repairs on this car & did not hear
from him at all for 10+ months.  We were unaware of any issues. He calls & says there is a problem with
the transmission/ clutch. He bring us parts & states that we put the wrong part. As we tried to explain to him we put the part that the...

catalogs at  multiple 
parts stores called for. At this point he
also told us that the transmission had been updated
modified  With hardened gears, we never
had it  apart to  verify this statement. If that's not true it was
just a misunderstanding.  We drove
it  after the engine
install & our technician did not state a driveline vibration at that time. If the customer had noticed something "ever since the engine install", it should have been brought back so we could check ou t the concern.We gave him a check for $450 as an agreed upon amount, he signed a statement
saying that he agrees
& we are not responsible. We have included a
copy of the signed agreement.