'Glee' Creator Ryan Murphy Trying to Make Amends With Original Cast Before Reboot

Ryan Murphy is trying to get back in the good graces of some of the OG "Glee" stars before he launches production on a reboot ... TMZ has learned.

Multiple sources close to original cast members tell TMZ ... Ryan's been reaching out to the actors to check in with them, and some view it as an attempt to make amends after years of strained relationships.

We're told some of the actors haven't returned Ryan's calls, as there's lingering bad blood over the show's first run.

Our sources describe Murphy as a "tyrant" who pushed the cast relentlessly, requiring weekend rehearsals for the "Glee" concert tours after the actors worked 15-17 hour days Monday through Friday.

Our sources say the cast felt they worked exhausting schedules while getting minimal raises, as Murphy and Fox profited heavily from the iconic franchise.

Of course, one could argue all that hard work is what made them, and the show, so famous ... and we're told some of the stars do acknowledge RM's role in their success. However, they also think he wasn't there for them during emotional hardships and was sometimes caused them.

We're told another issue for cast member is Ryan allegedly showing favoritism toward Lea Michele, and concerns she'll be the focal point of the reboot, too, is turning off some of the OGs.

Murphy recently said he'd finished writing a new "Glee" script, and that roughly 10 original cast members were enthusiastic about the idea. But sources tell us those remarks don't reflect the full story, because there's still "not a lot of love" for him ... at least for some of the actors.

We're told Murphy might be trying to mend fences before officially moving ahead with the reboot ... but it's unclear how many original cast members he'll end up using.