Maybe a stupid TRS question but:
 

If the counter rotating drive is the one that gives the most trouble, and its due to flexing, would if be beneficial to say fill the void for the exhaust with something like resin to stiffen it up?

Like i said may be stupid, but figured id ask.

boy i guess im not in the clique.

Define counter-rotating. I've always heard the LH drives were the "stronger" of the two versions.

The Left hand TRS drive does not change rotaion, the right and does change rotation. Yes, the left hand TRS is stronger due to the propshaft drive gear located in front of the pinion gear in the bullet. The right hand is prone to failure because the drive gear is behind the pinion, against the bearing carrier (that can move/flex somewhat) I've blown up my fair share of TRS units. typically they peel the rt hand pinion gear teeth out at the root. The wall thickness on the cases is rather thin and when subjected to more torque than designed, the case tends to flex altering the tooth contact pattern. -To answer your question, filling in the exhaust cavity might stiffen it up some but it's just going to add strength where it really isnt needed. Hope this bit of info helps. Kurt

Hard shimming them helps keep them alive....

100% agree with ya Kurt..

Ok. so I had the wrong one. So if the RH drive was to have the exhaust cavity filled with epoxy, do you think it would help? That would help transfer the force to the outer case houseing also, plus the epoxy would help to spread the load.

or is my thinking just completely wrong?

It could add strength but not where it is needed. The wall thickness of the gear case is rather thin where the lower vertical shaft roller bearing is located. As mentioned above, when subjucted to more torque than designed, the case flexes and throws off the tooth pattern. -Not an engineer, just have blown up a lot of TRS drives over the years.

As for hard shimming, (of the crush ring??) I've heard that it helps but I do not understand how it could as the crush ring is in front of the bearing carrier. -The propeller is driving the prop shaft into the forward bearing and the pinion gear is trying to push the carrier out of the case. Once the crush ring is crushed enough to provide proper rolling torque, I can't see how hard shimming this part would be able to increase strength.

thanks. It was just a thought. I guess i need to see inside of it to get a better understanding.