Did you simply remove the pinion drive flange from the original H150 diff, replace the seal, then refit the drive flange?

According to the book, this is a no-no.
These diffs use a collapsible sleeve to control the pinion bearing pre load & it is supposed to be replaced whenever the pinion drive flange is removed as it cannot be compressed any further once it has been set at the time of manufacture.

Unfortunately this involves a total strip of the differential including removal of the pinion in order to fit the new sleeve.

Anyway, have a read of the workshop manual & decide for yourself.