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I have been looking through search options to find photos of the gear change ratchet positions in associated gears, 1st, 2nd etc
I had thought someone had posted these before but I have failed to find them
Does anyone have these to share ?
email (option): Jonnyob1
Thanks Pete / Ron
This is what I was looking for - I have been distracted by other things here so I am back on the box again & want to finish & install the box this week
These pictures are good to have
Thanks for that - I am fully armed with the box rebuild documents but it’s small areas like the above I am missing out on
After my time spent on these gearboxes - it’s been a great learning curve & in some kind of sadistical way - looking forward to the next one lined up here for rebuild
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regarding the adjustment rod with locknut in those pics
riding my 44 M20 and changing into 4th its a hit or miss whether it actually goes into 4th, theres no noise and its smooth in operation but i have to go back to 3rd then try again, its so smooth in operation going through the gears but i cant help but think maybe i need to adjust that little rod, question is, which way?
it would save a lot of trial and error if someone knows
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Be always aware that there should be no backlash on the forks and clevis pins from the adjustment rod..the design not allowing any backlash .if there is backlash put new pins in..if there still is backlash redrill everything and put some oversize pins in.
What would happen if there is some backlash there, Roy ?
Would it be difficult to change gears ?
(I'm afraid every gearbox has at least some wear)
My gearbox sometimes has problems getting into 1 and 4 gear.
That's why I ask.
Roy is absolutely correct...Wear in various parts of the gearbox such as the pins and clevises mentioned, the selector fork tracks and pins, the selector fork ends and dog tracks or incorrectly shimmed shafts all result in excessive play and consequent 'lost movement'...The result of that is gears that don't fully engage with each other correctly or at all...Adjustments to the tie rod can be useful if the box has been incorrectly set up on assembly but cannot cure underlying wear or other issues...Ian
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Indeed ian.there is a needed travel between both parts but if the pins and other stuff have too much wear it ends up with especialy problems with 4th gear.i discovered this with my gearbox..without the adjuster mounted all the gears gone great.no problem at all..when i connected the adjuster rod the 4th gear most of the time missed..and guess about 1mm play on both sides from the adjuster..after oversize all of them and put in new pins it shift gears like new.
You know when the ratchet needs adjusting because it will affect 2 gears
So if 2nd & 4th don't select properly it will need to be longer
If 1st & 3rd don't select properly it will need to be shorter .
The usual culprit for poor selection of top is wear in the fork because you spend a lot of time in top gear
In theory once selected the dogs hold the gears in mesh ahd there is no contect between the fork & the sliding dog
In practice the undercut which lock the gears together gets worn down so the gear is held in play by the fork which will wear rapidly
Whenever you do a full rebuild it is worthwhile to get the dogs under cut again to restore the dovetails.
As you only have problems selecting 4th I would be suspecting the 3rd / 4th shift fork
I don't have any new gears or dogs here but in good condition the end face of the dog looks like a shallow pitched roof with a definate center line
Over time it wears to a dome shape
The slope is to aligh the gear & dog
The working faces ae slightly dovetailed to lock them together and where the dovetail and the end meet is fairly sharp corner on a new gear and of course a curve on a worn one
This prevents them locking together unless they are in sync with each other and the dogs can go fully home without touching each other .
[..'the end face of the dog looks like a shallow pitched roof with a definite center line'..]..
That is only true of one type of dog, the other type have a flat top face on the dog teeth...WD boxes of the wartime period used the flat top type though at this distance in time either type might be present...The gear dogs and selector dogs were originally of a matching profile in a given gearbox though the parts are interchangeable..Ian
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I had a problem like this , it turned out to be slight wear on a dog , replaced that and it was as smooth as silk, however on refitting the box/clutch etc it was a pain to get into 4th gear.
It turned out that the clutch was playing silly buggers but after adjustment and a good 100 miles it was ok so maybe it was bedding in ?? I also noticed I had to keep my foot held down sometimes to select 4th to get it to mesh correctly or it would jump out , so the box will have to come out again and replace the fork if it doesn't behave correctly .
I can honestly say I have rode plenty of m20s and most have strange neutrals doted around and are clanky, most of the old chaps say its just how they are and get on with it . however after I rebuilt my m20, apart from the above they are very smooth and easy to live with when set up correctly .
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