Originally Posted by
jethro00
We were able to take a test ride this morning.
As with my previous solo test ride, there was no chain slip.
So, that continues to make me believe the
3 sprockets on the intermediate shaft needed to be replaced.
Here is the data on the grinding in-line below in red in response to Jccaclimber's questions.
<<As for your grinding noise, it shouldn't be hard to track down, although we need a bit more information.
1. Is it coming from the front of the back or the rear? It seems to be located at the front.
2. Does it happen when both people pedal, when just one pedals, or when coasting? It does not make the grinding noise when coasting or when just the stoker pedals. It only makes the grinding noise when the captain pedals and it constantly makes the grinding noise when the captain pedals, whether or not the stoker also pedals.
3. Does it happen if you are not on the bike, ie with the rear wheel off the ground and you are turning one of the cranks by hand? I have a 2 sided kick stand that makes this very easy for me to test, but a stand, flipping the bike over, or having someone hold it up for a moment would all serve the same purpose. It does not happen with the bike on the stand or up on the 2-sided kickstand.
4. Does it happen in every gear, or just some of them? It happens in every gear.
5. What if you spin the intermediate shaft backward by hand (on the output side), without the rear wheel moving? It's not quiet when I spin the intermediate shaft backward by hand, but it's not a grinding sound.
6. Are all the bearings smooth? This is easier to check in the BBs if the chains (or drive side cranks) are not installed, but removal is not required.
I don't know. How do I check that?
This narrows it down quite a bit. It's somewhere between the captain's feet and the DFB.
My first guess from your description is captain's timing sprocket or BB, but you already replaced the timing sprocket, and a bearing needs to be pretty bad to make a grinding sound. I find the easiest way to feel a BB bearing is to remove the crank arms and rotate the spindle or bearings by hand while side loading them a bit. If it's inconvenient to pull the cranks off (mine are self extracting) then at least pulling the chain off will get you close. A smooth bearing feels just that, silky smooth. There may be some very mild seal drag, but it's still smooth (and likely no seal drag on bearings that have been in service a while). A bad bearing often feels like someone put some sand in it, and the balls are running into it.
If it doesn't happen normally on the 2 sided kickstand, you could try pedaling with the rear wheel off the ground while dragging the rear brake, but that really shouldn't be much different than riding normally. I suspect you'll find that the grinding gets louder with load.
Because it doesn't seem to matter if the stoker is pedaling I don't expect an interaction between the two freewheels on the DFB.
As another poster pointed out, this points to the captain's freewheel being worn enough that the chain slides a bit as it engages each tooth. I'd replace them both. Before you do that though, can you give us a nice clear picture of the freewheels? It's probably actually a bit easier with the chain still on, but we also need to be able to see the teeth where there is no chain.