I have a few sets of perfectly good Shimano MTB pedals where one of them has some play in the axel. Does anyone know how to fix this? I had someone in a shop tell me it’s not so simple, but seems to be a common enough problem that it must be a relatively straightforward fix.
In fact it’s very simple. You open up the pedal by the big 15/17 nut right next to pedal body and there is a little cup and cone assembly inside which you can adjust to get rid of the play. I don’t remember the exact wrenches it’s something like open end 9 and a 6 mm socket. One of the pedals assembly is reverse threaded.
If the inside is very dirty I flush the axle out with degreaser. If it’s just moderately dirty I just press fresh grease inside the pedal body and as I assemble the pedal back the fresh grease pushes out the old grease out.
Everything McSmokin said. It’s just another cup & cone bearing. I have two pair of M959’s and they’ve served me well with regular cleaning and only once did I have to adjust the bearings over I don’t know how many years.
That’s a lot of play though. There may be something else going on in there and the ball bearings may need to be replaced if they were ridden that loose.
The pedal axle nut itself is reverse threaded on one pedal. Thankfully that’s written on the pedal.
The cup and cone bearing requires a 10mm and a 7mm. The 10mm needs to be fairly thin to allow access to the 7mm. Thinner conventional 10mm spanners will work. Otherwise Park Tool CBW-1 is perfect.
When they’ve been ridden that loose for a while they’re a good chance you’ve damaged the bearings. That said, they’ll probably still last another decade….
This Park Tool video explains how to do it:
Note that some older Shimano pedals may require the medium-gray tool shown at the very beginning of the video: https://www.performancebike.com/shimano-tlpd40-pedal-axle-removal-tool-y42a09000/p325010
The fitting you put into vice jaws to hold the pedals is nice, but you can get by without it.
Sounds like it is time to find a new shop!!
Gotta love all things old Shimano and how easy they are to fix. I recall fixing up an old MTB during the pandemic to sell that had 90’s era Shimano entry MTB components on it. Pedals: Take apart replace bearings, clean up and lube, BB: Take apart replace bearings, clean up and lube Front and Rear Hubs: Take apart replace bearings, clean up and lube. Headset: Take apart replace bearings, clean up and lube. Cost: Likely less than a few dollars in bearings and pennies of lube.
Those appear to be XTR. If so, the external nut is 15mm, and the cone and locknut are 8 and 7mm. If the locknut has a groove in it, it is left hand threaded. Another indicator is if the external nut is right hand threaded, then the locknut is left hand threaded.
Once adjusted, I wipe the axle assembly with a rag. I thoroughly clean out the inside of the pedal body with degreaser, rag, and a screwdriver. Then I fill the pedal body about 1/3 of the way with fresh grease. If using a grease gun, it’s like 8 pumps. Then reinstall the axle assembly and tighten, turning the axle every couple turns of the nut to spin things around. Grease will purge out of the seal. On XTR, the axle seal likes to creep out of place, you can push it back in place afterwards.
Speaking from experience it gets a lot less simple when you drop all the little ball bearing on the workshop floor 
Thanks everyone! It was a bit fiddly but worked.
Here’s a photo of the nuts that needed to be tightened
Thanks for the heads up. Almost happened!
In the days when everything was cup and cone and loose bearings, I once had the idea that it would be nice to overhaul the bike while sitting in the sun outside on the lawn….
Trying to find ball bearings in a lawn does not make a happy cyclist. 
The “proper” way is to disassemble it completely and then degrease 
. Perhaps this is what the shop meant when they said, it’s not so simple. I managed to disassemble and clean, but failed to get the second row of balls back in place, they kept sliding down: https://youtu.be/-aewGJ1Pyfk?t=1036
After wasting quite some time I gave up and bought a new axle 
