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Thumbshifter Ratchet Pawl?

Old 03-19-22, 01:20 PM
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hotbike
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Thumbshifter Ratchet Pawl?


Shimano Deore DX Stuck in lower chainring


Shimano Deore DX with cover removed. Itís like a Swiss watch, itís got so many parts.


Trek 950 that Iíve added chopper handlebars and pannier/Tailbox with LED Lights to.

I took the cover off and doused it with WD40.
The ratchet will not engage, so I have to hold about 6 pounds of force with my left thumb to keep it in the middle chainring.

Do I have to buy a new one?
so far I donít think anything fell out .
maybe WD40 plus Road vibrations will unstick it.
IIRC, the pawl gets stuck account of dried grease, and this bike is 27 years old
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Old 03-19-22, 03:17 PM
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Those were made for only a year or 2 and that was 30 years ago. Toss them in the bin and get something else.
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Old 03-19-22, 03:21 PM
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You have to operate it while dousing with WD for best results.
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Old 03-19-22, 03:46 PM
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stuck pawl.

use a narrow dental pick & peer inside the mechanical workings for a spring loaded pawl.more than likely it can't move due to old gummed up grease.you need to use the pick to move it while spraying a thin lube on its pivot.look for a light colored rectangular shaped pawl.it engages the shark tooth gears.have only seen 1 that was chipped & couldn't be saved.with the rash on your shifter & maybe damaged but don't give up yet.DX is good stuff.
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Old 03-20-22, 03:58 PM
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I found that being able to move the pawl up and down on its shaft while applying a solvent, then next a lube, is about the best way to insure that shaft pivot if free of gummy old stuff. A few times (and early on with Shimano flat bar indexed shifters) pulling the "e" clip off the top of the shaft and removing the pawl was the way, but I leaned with experience removing the pawl is a rare need. Andy
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Old 03-20-22, 07:15 PM
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I worked on an a similar Shimano, but a lower tier level. I got all the advice about flushing and working it in, but to no avail. Eventuality I discovered that the coil spring was broken and displaced and pitched it and put on some simple friction thumbies. The Deore may be better, but maybe suffered the same fate.
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Old 03-20-22, 07:22 PM
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I had it apart earlier, and used a steel pick and WD40, to no avail.
I think the spring is broken. If it was dry grease, it would have come loose.
I have a spare left hand three ring grip shifter from another bike lying around, so Iíll probably install that.
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Old 03-21-22, 10:24 AM
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make sure there is no tension on the cable to cause the pawl to not move.
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Old 03-21-22, 02:44 PM
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Having a lot of fun assembling this beast



Traced outline of milk crate and handlebars on 12mm thickness polyethylene board


The bracket [ piece snap fits on the milk crate


The [ bracket snap fits on the milk crate


The plastic [ bracket snaps and locks the handlebars to the milk crate

Ive created a polyethylene bracket from 12mm thickness cutting board plastic.

Going to make a few more corner brackets, drill pilot holes, and screw it together.
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Old 03-21-22, 05:08 PM
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ditto everyone above with degreasing the pawl and moving with a separate tool. in the shop we will degrease them when the bike comes in, let it sit for 45 min or so, blast inside with an air hose, then add fresh degreaser while moving the thumb paddles around until we could get just one click. after that switch to tri-flow and a pic/awl to move the ratchet pawl around until the spring tension overpowers the old lube/grease
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Old 03-21-22, 05:27 PM
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Originally Posted by mauricesnail View Post
ditto everyone above with degreasing the pawl and moving with a separate tool. in the shop we will degrease them when the bike comes in, let it sit for 45 min or so, blast inside with an air hose, then add fresh degreaser while moving the thumb paddles around until we could get just one click. after that switch to tri-flow and a pic/awl to move the ratchet pawl around until the spring tension overpowers the old lube/grease
Wow. But the key is , you never actually *disassemble* the mechanism, I take it?
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Old 03-22-22, 05:38 PM
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Originally Posted by hotbike View Post
Wow. But the key is , you never actually *disassemble* the mechanism, I take it?
haven't needed to, honestly it wouldn't be worth the cost of labor compared to replacing. that said we'll degrease ~50 shimano 7/8 thumb shifters a year the way described.

as a side note none of the ratchet gears, pawls, or springs ever appear damaged, just gunked up, and in the past five years it's become of more common problem. guess the manufacturer's grease from that era is reaching its expiration date? correlation, etcetc
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Old 03-22-22, 06:09 PM
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Originally Posted by mauricesnail View Post
haven't needed to, honestly it wouldn't be worth the cost of labor compared to replacing. that said we'll degrease ~50 shimano 7/8 thumb shifters a year the way described.

as a side note none of the ratchet gears, pawls, or springs ever appear damaged, just gunked up, and in the past five years it's become of more common problem. guess the manufacturer's grease from that era is reaching its expiration date? correlation, etcetc
Iíll have to plug in the compressor to supply the air.
By degreaser, do you mean WD40, or the engine cleaner stuff?
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Old 03-23-22, 03:54 PM
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Originally Posted by hotbike View Post
Iíll have to plug in the compressor to supply the air.
By degreaser, do you mean WD40, or the engine cleaner stuff?
chef's choice, maybe double check whatever you use doesn't melt plastic (actual problem)

if ya got a bike shop nearby see if they have any degreaser they could spray in there, very unlikely they'll have anything too caustic compared to the auto zone apothecary. good luck!
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Old 03-23-22, 04:18 PM
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Originally Posted by mauricesnail View Post
chef's choice, maybe double check whatever you use doesn't melt plastic (actual problem)

if ya got a bike shop nearby see if they have any degreaser they could spray in there, very unlikely they'll have anything too caustic compared to the auto zone apothecary. good luck!
Iíll probably replace it with a grip shifter from another Trek I got from the same curb alert.
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Old 03-23-22, 07:25 PM
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Originally Posted by mauricesnail View Post
chef's choice, maybe double check whatever you use doesn't melt plastic (actual problem)

if ya got a bike shop nearby see if they have any degreaser they could spray in there, very unlikely they'll have anything too caustic compared to the auto zone apothecary. good luck!
We use (recently banned in NYS) a solvent and basin from Safety Kleen and the effects on the plastics of these shifters is one of expanding the part's size. Specifically a version of these STI shifters have a plastic band that acts as a grit shiels and sits between the two "clamshell" halves of the shifter cover. If the shifter is left soaking in the solvent this shield absorbs something and swells. The couple I have left to dry never seemed to shrink back to OEM size. Si I strongly advise if the shifter has such a band/shield that it's removed before solvent work. Andy
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Old 03-28-22, 12:42 PM
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Not Shimano, not Shimeng, not Magna....


30 year old bikeís are hard to find parts for.
I had to settle for this aftermarket thumb shifter.
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