Club126UK
Fiat 126 Chat => Fiat 126 Mechanical Problem Solving => Topic started by: Bambino126 on April 30, 2015, 08:50:33 PM
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So I've got my new second-hand gearbox back in to the car now, but before fitting the engine I decided to check the gears. I got into the car but cant select anything, its just stuck.
So I've undone the gear linkage snubber and tried to turn it by hand. It moves left and right a little like you were swishing through neutral but it won't move in and out of the box to select a gear.
Next I've pulled the gearbox out of the car all over again and opened up the tail section to check the selecter rod isn't jammed or something.
The three rods that I think are used to select the gears dont move at all (even with a light hammer tap) I've coloured them with the red arrows in my photo. Is it meant to be like that? Would you expect not to be able to select any gears until the engine was reinstalled in the car?
When you turn both the driveshafts in the same direction the input shaft turns so its not seized and its obviously in a gear at the moment you just can't change it.
I don't know very much about gearboxes so I thought I'd better check this before going any further.
Thanks
(http://i46.photobucket.com/albums/f101/tashman_/IMAG0228b.jpg) (http://s46.photobucket.com/user/tashman_/media/IMAG0228b.jpg.html)
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It is very possible to change the gears with the box out as it were - and they should slip in and out without any fuss. The way I do it is to keep the gear shift rubber coupling on the box (the part with the rubber circle in the middle) twist it ,doesn't matter which way as like you say that is neutral then give the selector a light tap and it should engage a gear. Tap it from behind whilst holding it straight and it should go back into neutral again. There doesn't look to be anything untoward with the selectors in that photo so it could be that there just stiff from being idle for some time and are just a bit dry. Give the selectors a good dousing with brake cleaner. If you remove the lid on the top of the gearbox you'll see all the gears. It's possible again to select certain gears by very carefully levering them with a long screw driver.
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It is not easy to engage any gears from the selector shaft when the gearbox is out of the car. The gear lever has a huge mechanical advantage when in the car. The detent springs and ball bearings locate the selector fork shafts in position quite firmly. You can release the small plate on the side of the gearbox which will relieve the spring tension and allow easier movement of the shafts. If they still do not move then there may be a problem with the ball and slider at the far end of the shafts but that would only happen if the gearbox had been wrongly assembled.
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I just tried removing the small plate that covers the detent springs to release the pressure. Now one of the selector folk shafts moves very easily by hand. The other 2 are still stuck. Its the top shaft in my first photo that's free to move now.
After that I went over to my old broken gearbox and did the same thing - undid the detent spring plate. Suddenly the top selector shaft became free on that box too.
So maybe that's all that's meant to happen? :-
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Hmm... Even more worrying is this round grinding hole that's being made inside the tail cover.
Looks like the main gear shaft has been trying to tunnel its way out in a bid for freedom :o
(http://i46.photobucket.com/albums/f101/tashman_/Mobile%20Uploads/IMAG0229.jpg) (http://s46.photobucket.com/user/tashman_/media/Mobile%20Uploads/IMAG0229.jpg.html)
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As Gadge says, if you take of the 4 bolts holding on the black cover then all should be revealed. I cannot remember the details but there is a detente mechanism in the selector fork assembly that prevents movement of the shafts ie with one selector engaged the others may well be be locked out. I wouldn't worry too much about the witness mark you mention unless you find other damage but end-float would be shimmed out during a gearbox rebuild. Its important that the gear rod locates correctly into the selector fork slots when you replace the end cover. I have a partly dismantled spare gearbox if you are stuck for bits.
Keith
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The bottom (reverse I think) selector pulls out to engage if I remember correctly. Thus, make sure you try the rods in both directions ;D
Keith
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As Gadge says, if you take of the 4 bolts holding on the black cover then all should be revealed. I cannot remember the details but there is a detente mechanism in the selector fork assembly that prevents movement of the shafts ie with one selector engaged the others may well be be locked out. I wouldn't worry too much about the witness mark you mention unless you find other damage but end-float would be shimmed out during a gearbox rebuild. Its important that the gear rod locates correctly into the selector fork slots when you replace the end cover. I have a partly dismantled spare gearbox if you are stuck for bits.
Keith
Spot on! When one shaft is pressed the others are locked out and cannot be pressed.
My fault was the gear rod was not located properly into the selector folk slots like you said. It took a while bit I figured out how to get all 3 rods into neutral then fit the gear rod then the cover. Works a treat now!
Without the help and advice of this forum, I would be nowhere. Thanks guys.