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Discussion Starter · #1 ·
I recently replaced my shift cable (GX shifter and derailleur) because the motion was starting to feel a bit gunky. After I did that the shifting became worse than it was before. It downshifted to bigger cogs fine but upshifts were super slow. I'd have to over shift a couple of detents to make the chain move over then I'd have to downshift back to get to the gear I wanted.

I therefore replaced the entire housing and cable with a Jagwire Pro Shift kit. Downshifts are nice and smooth, like they should be, but upshifts are still super slow. When I click the shifter it'll take several seconds for the chain to hop over to the next smallest cog.

I didn't touch the derailleur setup or B-adjustment. They're where they were set by the LBS that built up my bike. Shifting was fine up until recently.

What should I check, adjust, or replace next?
 

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check the hanger for alignment and play with cable tension. Cable sounds too tight if it won't upshift. Or hanger is out.

Suppose on a long shot the derailleur pivots could be dry and/or if you have a cable guide on your bike, maybe a drop of lube so the cable moves smoothly on the return.
 

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Discussion Starter · #4 ·
Cool. In my smallest cog the cable feels just a hair slack. When I downshift the chain will climb up to the next cog quickly and smoothly. When I upshift once the chain decides to move over it’ll land on the smaller cog and then it doesn’t try to jump either up or down. It just takes its own sweet time getting there, like it can’t be bothered.

I tried lubing the pivots after my ride tonight. I’ll see tomorrow if it makes shifting faster.

The hanger appears straight to the eye and I haven’t taken a fall on the drive side recently. I wonder if the LBS has an alignment gauge?

Is there any way to increase spring tension on the GX derailleur? I had an older SRAM derailleur that had an adjustment screw but I didn’t see anything similar on this new one.
 

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I'm a bit cynical about this, but the only thing we were able to do to improve it, after going through two GX derailleurs, was to replace the derailleur and shifter with XT when they were released. This solved the problems.
 

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Discussion Starter · #6 ·
I'm guessing you've tried loosening the cable tension? If you loosen it enough to upshift smoothly will it then not downshift?
I did. I anchored the cable to where it is a touch slack in the smallest cog and I started with the barrel adjuster about one full revolution out. I was therefore able to play with increasing and decreasing tension via barrel adjuster to where the chain would start to want to move either direction from any of the central cogs.

I haven't been able to get it to upshift well yet regardless of the cable tension. The chain will eventually find the smaller cog and run smoothly once it's there but it just takes forever to get there. It's like it's sleepy on upshifts.
 

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Discussion Starter · #7 ·
I'm a bit cynical about this, but the only thing we were able to do to improve it, after going through two GX derailleurs, was to replace the derailleur and shifter with XT when they were released. This solved the problems.
I've actually been wondering if my shifter and derailleur are just getting older and full of friction, or if the return spring has weakened. Buying a new shifter and derailleur isn't out of the question so if that's my next move then I can do it.
 

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I've actually been wondering if my shifter and derailleur are just getting older and full of friction, or if the return spring has weakened. Buying a new shifter and derailleur isn't out of the question so if that's my next move then I can do it.
IME it would be extremely unusual for the shifter and/or derailleur to cause that problem.

If you loosen the tension even more will it upshift 2 gears instead of 1?
 

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Remove the cable from the housing, working it back and forth, just to make sure the housing is clear.
Is the new housing set to equal length of what it replaced, and in the same path?

You probably won't be able to see if a hanger is tweaked by eye. Your local shop will have the hanger tool (for them to use).
 

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I'm wondering how it behaves if the cable is removed from the scenario entirely.

Detach it from the derailleur, and work the derailleur by hand. Downshift manually by pushing on the derailleur. Let go of it and let it upshift on its own. Still sluggish?
 

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completely re-do the derailleur adjustment. Sounds to me like indexing may be off, b-tension as well and potentially a bent hanger.

For the people suggesting going to shimano over sram... that's not a solution to this problem. Until you take the responsibility of correcting your drivetrain and shifting issues yourself with proper adjustment... you're playing drivetrain roulette. Sure if you make the swap the new stuff may shift better for a bit, but then something will get knocked or wear into out of spec and the same thing will happen.

You should be checking the setup and adjustment of your drivetrain at least once a month. If you don't know how to do it, spend 2 hours on youtube and educate yourself. Your LBS should not have to setup, adjust or correct your drivetrain.
 

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What I've found with GX 12 speed is the derailleur main bushing wore out rather fast. It looked like my hanger was bent but it wasn't. The result was sloppy shifting I couldn't correct no matter what. It also had a ton of play in it. Hard to armchair your problem beyond what was said but certainly sounds like the symptoms of a grabby cable. In addition to what Harold suggested grab the cable when you have it off, pull on it and index through all the gears. All else being correct hopefully that will make the culprit stand out.

We need to start pools with these threads. I'm taking the shifter for $5.
 

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Discussion Starter · #13 ·
Follow up:

Last night I lubed each pivot point on the derailleur. Today I released the cable entirely like Harold suggested and manually ran the shifting, which did allow fast upshifting. I loosened the cable even further to where it felt quite slack in the smallest cog, then took up just enough slack with the barrel adjuster to allow a decent downshift.

On my ride today it started out a bit clunky with skipping but by the end the shifting felt much improved. I'm not sure if I'd call it perfect but it's way better than it was yesterday.

Thanks for your input everyone!
 

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I know you said you did not touch the b screw and it shifted well previously but this sounds like the EXACT symptoms I've had which were finally resolved through b screw adjustment. I'd tried tweaking tension over and over again, checked the hanger alignment, bought new cable/housing to try, and was regretting not buying a Shimano XT drivetrain until I finally bought the red sram guide and used it to set the b screw juuust right. And it finally starting shifting perfectly. If you have a full suspension bike you are supposed to set it with the shock sag so you may need to either let some air out or get a friend to help. I'd previously measured the pulley to cog distance with a tape measure but apparently didn't get as accurate of a measurement as needed.

Sent from my SM-G955U1 using Tapatalk
 
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