ORIGINAL: matador_24

Man, I can say I have a LOT of experience in crashing and replacing parts.... I have crashed 24 times....

First of all, after any crash you have to replace the FEATHERING and MAIN SHAFT, specially if your main blades were damaged, for sure those 2 shafts will be as well, even if they don't seem to be damaged, sometimes they have been slightly bent that you don't see it but they WILL give you trouble after, just replace them after EVERY CRASH, don't even think about it, that is important if you want to have always your heli flying properly and with a good blade tracking, believe me, I learned the hard way.....

After a crash, it's important also to check your tail bool, the servo gears and the main gear, what you say about the noise, it's probably the main gear that was damaged, even if there is a little little tiny bit of gear chipped, it will affect most of the times and it will make that noise, before crashing, try to swtich the antirotation switch in order to avoid stripping the main gear (the switch that is usually at the right of the transmiter).

Really, don't waste time trying to figure out the problem, replace the parts I said and I almost guarante you that it will work excellente again, man, one thing I learned about the t-rex is that is a wonder of the world, you just have to replace the parts and it will fly as BRAND NEW again, even if you crash once and once again, anyway, if you replace the parts and some of them were not the problem you can keep them as spare for after, but you have more chances to succed in solving your problem.

I hope this is usefull

P.S. If your main shaft was bent, I am 99% sure that your feathering shaft is bent as well.