Noisy Giant / Yamaha SynchDrive

[HBrook78]

I have a 2018 Giant Explore e+3 with about 6K miles on it. It has a Yamaha SynchDrive. Today, the drive started making noises that sound like a bearing is failing. Full symptoms:
- Noise is like 3 or 4 BBs rattling in a water bottle with occasional louder pops
- Volume of noise is proportional to the amount of torque the drive is providing
- No noise when coasting
- I can make the noise come and go…for example, if I am going slightly down grade in 5th gear and pedaling gently in “normal” assist setting, no assist is delivered and there is no noise. If I pedal harder and the display shows assist being delivered, the noise appears. If I reduce my pedaling effort, the noise goes away again.

Has anyone here had a similar experience? I’m taking it to my Giant dealer tomorrow but I always prefer to have a good idea what to expect.

TIA.

 

[gorse]

What was the outcome? My motor is doing the same sort of thing, feels like drive gear wear..

 

[Andee]

I've twice experienced this with Giant SyncDrive Pro2 motor. On the first occasion it was due to misalignment of the main drive gear following a hard pedal strike. It was an easy fix. No parts needed (although this requires being comfortable with opening the motor yourself). The second occasion was interesting as it sounded and felt almost identical. It took me ages to diagnose it. Turns out the issue was due to fitting a new chain that wasn't dropping freely off the chainring. This was causing vibration feedback through the motor housing that sounded like grinding cogs. So that was good lesson in not assuming the problem is what it seems. It may be something else entirely.

 

[HBrook78]

What was the outcome? My motor is doing the same sort of thing, feels like drive gear wear..

The dealer couldn’t find a problem but I kept poking at it. It turned out to be bad pedals . I did find some places that rebuild drives for about $400. The dealer said the Giant repair process is slow. My drive is still working fine. What I was feeling was worn out bearings on the pedal shafts. The bike still makes a sort of a rhythmic creak but I think that’s probably associated with the saddle. Got some nice Shimano mountain bike pedals to replace the OEM parts….a real upgrade .

The motor rebuilder is here: https://ebikemotorrepair.com/?v=0b3b97fa6688

 

[HBrook78]

What was the outcome? My motor is doing the same sort of thing, feels like drive gear wear..

UPDATE…i was getting a persistent creaking noise while pedaling today. It was present only while pedaling and whether the motor was on or completely switched off. I got the bike up to a descent clip and then downshifted while maintaining the same speed. The frequency of the creaking (not pitch, rather creaks per minute) increased which confirmed that the noise was coming from the crank.

When I got home, I checked for excessive play in the crank bearings by trying to wiggle the shaft. To my surprise, I found that the entire motor assembly was moving WRT the frame. I found the torque spec for the bolts (30 N-M) and I plan to tighten them and test ride tomorrow. I will post another update after that.

 

[HBrook78]

UPDATE…i was getting a persistent creaking noise while pedaling today. It was present only while pedaling and whether the motor was on or completely switched off. I got the bike up to a descent clip and then downshifted while maintaining the same speed. The frequency of the creaking (not pitch, rather creaks per minute) increased which confirmed that the noise was coming from the crank.

When I got home, I checked for excessive play in the crank bearings by trying to wiggle the shaft. To my surprise, I found that the entire motor assembly was moving WRT the frame. I found the torque spec for the bolts (30 N-M) and I plan to tighten them and test ride tomorrow. I will post another update after that.

Final Update. I got about 1/8 turn out of each of the 3 mounting bolts to get to 30 N-m torque. Problem solved. Something to check periodically going forward. I found a service manual for the 2020 versions of Giant / Yamaha SynchDrives here: https://www.manualslib.com/manual/1818637/Giant-My20.html?page=11