Gear 6 and 7 not working/engaging on Shimano Nexus IGH
04-22-24, 04:54 AM
#1
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Gear 6 and 7 not working/engaging on Shimano Nexus IGH
Hi Bikeforum
I have several bikes with Shimano Nexus 7 IGH. On one of them I have experinced a rather odd issue. After not being ridden for some months gears 1-5 work flawlessly but nothing happens when selecting gear 6 and 7. It feels as though it is somewhat lower than gear 5 when selecting gear 6.
I have disassembled, cleaned and greased the hub with IGH grease according to the assembly instructions available from Shimano. Cable pull is checked and adjusted. And found no obviously damaged parts og stuck movement. But it somewhew seems like the mechanism that should select gear 6 and 7 does not active/engage when everything is assembled
Anyone experienced similar issue?
I have several bikes with Shimano Nexus 7 IGH. On one of them I have experinced a rather odd issue. After not being ridden for some months gears 1-5 work flawlessly but nothing happens when selecting gear 6 and 7. It feels as though it is somewhat lower than gear 5 when selecting gear 6.
I have disassembled, cleaned and greased the hub with IGH grease according to the assembly instructions available from Shimano. Cable pull is checked and adjusted. And found no obviously damaged parts og stuck movement. But it somewhew seems like the mechanism that should select gear 6 and 7 does not active/engage when everything is assembled
Anyone experienced similar issue?
04-22-24, 12:34 PM
#2
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The clutch that engages the driver to the planet carrier must be failing to engage.
In gears one through 5, the driver transmits input torque to the reduction ring gear and the power flows from that ring gear through different combinations of engagement of four sun gears. In 6th and 7th, sun gears one and two as well as the reduction ring gear are taken out of play as the clutch engages the planetary carrier directly.
The reason for this failure could be any one of a number of things. Corrosion, wear, breakage, or just lack of lubrication.
In gears one through 5, the driver transmits input torque to the reduction ring gear and the power flows from that ring gear through different combinations of engagement of four sun gears. In 6th and 7th, sun gears one and two as well as the reduction ring gear are taken out of play as the clutch engages the planetary carrier directly.
The reason for this failure could be any one of a number of things. Corrosion, wear, breakage, or just lack of lubrication.
04-22-24, 12:47 PM
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I always check dropout alignment first before troubleshooting anything else.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
04-22-24, 01:04 PM
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I always check dropout alignment first before troubleshooting anything else.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
No RD.
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04-22-24, 01:04 PM
#5
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Thread Starter
I always check dropout alignment first before troubleshooting anything else.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
Once that is good, then I check that a RD should also totally remain in parallel to itself no matter how it's wound, either all cramped up as it's removed, and dangling out with a chain there.
Once those two are verified, then I go ahead and make sure it's springy everywhere and pivots freely.
Those jockey wheels should also spin on their own momentum. They are often rebuilt with grease which is wrong and hardens them up.
04-22-24, 01:07 PM
#6
Newbie
Thread Starter
The clutch that engages the driver to the planet carrier must be failing to engage.
In gears one through 5, the driver transmits input torque to the reduction ring gear and the power flows from that ring gear through different combinations of engagement of four sun gears. In 6th and 7th, sun gears one and two as well as the reduction ring gear are taken out of play as the clutch engages the planetary carrier directly.
The reason for this failure could be any one of a number of things. Corrosion, wear, breakage, or just lack of lubrication.
In gears one through 5, the driver transmits input torque to the reduction ring gear and the power flows from that ring gear through different combinations of engagement of four sun gears. In 6th and 7th, sun gears one and two as well as the reduction ring gear are taken out of play as the clutch engages the planetary carrier directly.
The reason for this failure could be any one of a number of things. Corrosion, wear, breakage, or just lack of lubrication.
I am also wondring if the last bit of movement to engange 6th and 7th gear is somewhat not happening due to excess friction. Bu when disassembling the hub the sliding cluth seems to work freely and without issues. Cannot see if that is also the vase shen everyhting is assembled.
THere is no rust and everyhting is frencly cleaned cunked in shinamnos service kit oil + grease on the bearing
04-27-24, 02:21 AM
#8
Senior Member
I'm not an authority on this hub.
I'm very impressed that you pulled the hub apart, cleaned and regreased it.
The aforementioned clutch to engage gears 6 and 7, what kind of clutch is that? A dog clutch (like interlocking your fingers), ratchet (pawls, springs, and teeth), sprag (overrunning; balls and wedges), or some sort of flat disc friction clutch or cone clutch (like synchronizer rings)? If a friction clutch, I wonder if some sacrificial surface has worn sufficient so that there is insufficient travel or spring force for high force engagement?
I'm very impressed that you pulled the hub apart, cleaned and regreased it.
The aforementioned clutch to engage gears 6 and 7, what kind of clutch is that? A dog clutch (like interlocking your fingers), ratchet (pawls, springs, and teeth), sprag (overrunning; balls and wedges), or some sort of flat disc friction clutch or cone clutch (like synchronizer rings)? If a friction clutch, I wonder if some sacrificial surface has worn sufficient so that there is insufficient travel or spring force for high force engagement?
Last edited by Duragrouch; 04-27-24 at 02:25 AM.
04-27-24, 03:10 AM
#9
Newbie
Thread Starter
I'm not an authority on this hub.
I'm very impressed that you pulled the hub apart, cleaned and regreased it.
The aforementioned clutch to engage gears 6 and 7, what kind of clutch is that? A dog clutch (like interlocking your fingers), ratchet (pawls, springs, and teeth), sprag (overrunning; balls and wedges), or some sort of flat disc friction clutch or cone clutch (like synchronizer rings)? If a friction clutch, I wonder if some sacrificial surface has worn sufficient so that there is insufficient travel or spring force for high force engagement?
I'm very impressed that you pulled the hub apart, cleaned and regreased it.
The aforementioned clutch to engage gears 6 and 7, what kind of clutch is that? A dog clutch (like interlocking your fingers), ratchet (pawls, springs, and teeth), sprag (overrunning; balls and wedges), or some sort of flat disc friction clutch or cone clutch (like synchronizer rings)? If a friction clutch, I wonder if some sacrificial surface has worn sufficient so that there is insufficient travel or spring force for high force engagement?
It is a sliding clutch that seems to engange some pawls when sliding. These pawls then engage the ring gears for 6th and 7th gear. But it seems that even shtough the lcuth is lsiding fine when disassembled - when everything is assembled it does not seems ti slide. Maybe something is sligly bent or there is excess friction
04-27-24, 05:52 PM
#10
Senior Member
I have disaasmbled and cleaned/lubed many of these hubs. So luckily o know how to. I tis quite simple and does not require specialty tools
It is a sliding clutch that seems to engange some pawls when sliding. These pawls then engage the ring gears for 6th and 7th gear. But it seems that even shtough the lcuth is lsiding fine when disassembled - when everything is assembled it does not seems ti slide. Maybe something is sligly bent or there is excess friction
It is a sliding clutch that seems to engange some pawls when sliding. These pawls then engage the ring gears for 6th and 7th gear. But it seems that even shtough the lcuth is lsiding fine when disassembled - when everything is assembled it does not seems ti slide. Maybe something is sligly bent or there is excess friction
04-28-24, 01:41 AM
#11
Newbie
Thread Starter
For information I have fixed the issue now. Thank you for all the suggestions
I fully disassembled the axle as per instructions on sHeldons site and reassembled. I found out that one of the tabs for the parts resposible for shifting into 6th and 7th gear were slightly bent. Meaning taht the notches pushings these tabs could not get e grip. I bent them into correct position and all shift fine now.
I suspect this happened due to ecessive load on the hub during fwinter with very hard cable pull.
I fully disassembled the axle as per instructions on sHeldons site and reassembled. I found out that one of the tabs for the parts resposible for shifting into 6th and 7th gear were slightly bent. Meaning taht the notches pushings these tabs could not get e grip. I bent them into correct position and all shift fine now.
I suspect this happened due to ecessive load on the hub during fwinter with very hard cable pull.
