Murriel wrote:

Model GT2550

Instuction manual says to change the transmission filter after the
first 10 hours of use, but that you can replace the fluid that was
drained out as long as it was kept free from contaminants.

1) Why is it necessary to replace this filter after the first 10
hours?

More crud will be generated / loosened and hence filtered during the
break-in period.


2) Doesn't it seem self-defeating to put the "used" oil back in the
transmission case? Thanks.

No, since the filter has filtered it, however it seems more hassle to
make sure the drain pan and surrounding area is clean when draining,
then wrestle with trying to funnel the oil back in, than to open a few
dollars worth of new oil to pour in.