Normal to have minor noise variation in 3 futaba bls351s

[amphibia]

Hi all,

I recently acquired 3 used futaba bls351s from a local 600-class scale flyer. I know him well and trust him on the no-crash-and-less-than-50-flights statement. He assured me there was no abuse of any sort. These servos did sit in the garage for probably 1-2years.

However, as I power them on, each bls351 makes a slightly different noise, no1 is pretty quiet and have that smooth sound (similar to all-plastic-gear bls251 sound). The other two bls351s are noisier. No3 is noisier than no2. But hand turning no2 has ever so tiny slightly notchy feel at 2 spots.

I opened no1 and no3, took out all gears, and let the motors run. They both run smoothly but no3 motor is definitely noisier than no1, but the difference is no where near the difference between no 1 and 3 when all the gears are put in.

They all run accurately with similar freeplay as another set of brand new futaba bls253s


So tell me, should I be worried about no2/no3? Are there definitive tests to diagnose brushless servo motor/gear issues? Am I crazy or OCD?

Many thanks in advance.