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Shimano Nexus 7 IG hub, can't get 6th and 7th gears

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Shimano Nexus 7 IG hub, can't get 6th and 7th gears

Old 09-05-12, 05:49 AM
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impert
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Shimano Nexus 7 IG hub, can't get 6th and 7th gears

Hi all,

I have a Shimano Nexus 7 internal gear hub (SG-7R46, no brake) bought in 2008.
I have a problem with the top two gears, a problem which has already happened (eight years ago) to someone else on this forum, whom I quote:

http://www.bikeforums.net/archive/in...p/t-46550.html

03-26-04, 08:21 AM

The bike shifts fine 1st through 5th gears, but when you try to shift to 6th or 7th gear, you get gears that are lower (faster spinning/fewer gear inches) than the 5th gear. Puzzling.
That describes my problem exactly.
I have disassembled and re-assembled the hub in accordance with the Shimano service manual. I could find no damage at all: no damaged or gummed-up pawls, no sign of water or dirt, no metal particles in the grease, in fact it looked new.

I have tried adjusting the cable first (obviously) according to the book, then a little tighter and a little slacker than recommended. It makes no difference until it is so grossly maladjusted that I have problems with the other gears too. The cable runs freely and is correctly led. The gear selector, I think an SI-RS41D, is a Shimano 7-speed one bought at the same time as the hub, and presumably correct. At any rate it all worked very well for about three years.

The five lower gears all work perfectly, with no noises, and the wheel spins very freely.

Unfortunately the bike shop I bought it through has gone out of business.

Does anyone have any ideas? I couldn't find anything on the Shimano site, nor anywhere else on the web, for that matter.
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Old 09-05-12, 05:15 PM
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Heh, I had a similar issue and read that post a couple years ago. Assuming you have perfect cable routing (my Alfine was very particular, one straight line to the cable anchor is the best idea. Don't cut the stock cable.) any chance you are using the Nexus Revoshifter? I found that shifter to be a piece of junk. IMO it's worth while to buy the better one, or better yet the J-tek barend shifter for Alfine. Also, my Alfine 8 was very picky about shifting under load.
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Old 09-06-12, 06:12 AM
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Thanks for the reply, Aquakitty.
I really don't think it's the shifter, or the cable. It all worked very well for quite a while, and the cable still seems to move correctly. If the cable movement had been wrong, I think I would have found some change by adjusting it tighter and slacker.

(Not sure if it's a revoshifter or not, it just says shimano nexus, with a red line. It's a twist type. On the underside of the aluminium casing that has the brake lever pivot there is "SG-7S40", the SI-RS41D came from the multilingual installation instructions.)

Did changing the shifter fix yours?

Last edited by impert; 09-06-12 at 06:18 AM.
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Old 09-06-12, 08:20 AM
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From what I know about the way the Shimano IGHs work, there's a possibility that this is due to an internal problem with the hub. Basically, some hub gears work by using multiple "stages" of gearing, and if one stage has failed or isn't engaging properly, this sort of thing can happen. How much use has the hub had?
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Old 09-06-12, 08:43 AM
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Originally Posted by Airburst View Post
From what I know about the way the Shimano IGHs work, there's a possibility that this is due to an internal problem with the hub. Basically, some hub gears work by using multiple "stages" of gearing, and if one stage has failed or isn't engaging properly, this sort of thing can happen. How much use has the hub had?
I don't have an odometer, and I ride pretty irregularly, using several bikes, so the answer is the wildest of guesses: perhaps 3000 - 4000km, much of it since the 6th and 7th stopped working.
I didn't pull it down immediately, partly through fear, partly because I was too busy with house renovations, and anyway it's quite rideable in the other gears. (And it's made me increase my cadence, which is supposed to be a good thing.)
I expected to find something like a jammed/broken pawl, or at the least a burr that stopped something sliding properly. I'm starting to wonder if I hit a pothole hard, or came off a kerb, and maybe bent something in a fairly subtle way. I just can't remember.
Trying to figure out what should happen when you've got it apart is not obvious; the things are pretty complicated.
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Old 09-06-12, 02:45 PM
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Oh this is something that just started happening? Mine was like that out of the gate but with the middle gears. Yes it was the Nexus twist shifter and that fixed it, however in your case it could be anything if it was fine at first. The shifter could be worn, pretty hard to say without seeing in person. They can be had for under $10 so pretty cheap way to see if that's the problem. Doesn't sound like it though if you had it working fine for 3 years.
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Old 09-06-12, 03:09 PM
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Originally Posted by Aquakitty View Post
They can be had for under $10 so pretty cheap way to see if that's the problem.
I can't remember the price, but it was a good deal more than that, and had to be ordered.
There's a not-so-local bike shop about 70 km away which has a Shimano franchise, but I doubt if they have much experience with IGHs - I haven't seen another on the road here. I suppose I'll end up going there. I was just hoping someone would say "that's a common problem, all you have to do is hit it with a sledge hammer while riding flat out in 5th gear facing backwards" or some such.
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Old 05-01-15, 10:53 AM
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I have similar problem only with 1 and 7 gear not engaging. 1 stopped working after few days when relubing hub. And felt almost no difference when shifting to 7. Which parts of hub are responsible for these gears?
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