I made a new gear linkage
Discussion
Well my GTO 3 shift linkage was driving me up the wall - stirring a sloppy pudding sprang to mind. All the GTO's I test drove were the same so this cannot be specific to just my car.
Not willing to part with calculator figures for the upgrade (I am sure it is nice enough
) and as I hand built an entire linkage for my rally car I felt like having a look to see what I could do to make things a bit better.
I haven't finished addressing all of the issues but I did spend the weekend resolving a few things and I thought I'd share my findings thus far with you.
First port of call was a broken Terry clip that is mounted on the gearbox casing underneath one of the shift linkages. The factory fitted one of two types and Simon in the Stores kindly supplied me with both. More common was a 'stiffer' type and it was found that this is what my car had originally fitted - albeit through general metal fatigue it had broken. A fairly swift swap for a new one had the gear lever spring tension restored in the centre/left plane.
However, it occured to me that part of the problem of the undersprung tension at the gear lever end is due largely to the distance between this Terry clip on the gearbox and the gear lever itself, which has no separate spring tension. I wanted to address this issue in the overall plan.
Having removed the gear knob, gaiter and silver trim cover I spent a while studying the existing linkage and noticed that there is an amount of play where the upper pivot linkage connects to the chassis bracket. Upon removal I found that this is not due to wear but due to the play in the threads linking the rod-end to the bracket. As it has to move in 2 planes it cannot be tightened up or you wouldn't get the left/right motion at the gear lever.
My plan therefore was to replace this system with a nice snug ball and socket affair, with further spring assistance at the gear lever end and also reducing the 'throw' of the lever at the same time.
Hunting around I found a linkage from a Toyota that could be modified to suit. It was compact enough for the intended application but the gear lever only extended upwards of the ball & socket and a bit of modding was in order. So having removed the lever from the ball I then removed the material from the bottom of the socket cup to allow for a new lever to pass through.
Next I made the new lever having calculated the relevant pivot point distances to the top and bottom of the lever - and introduced an approximate 20% less throw. This new lever passes through the ball and was welded to keep it firmly in place. I then cut a new M12 thread at the top so that the stock gear knob could be replaced when it was all back together.
I did not want to chop up any of the original lever or its parts so I copied the lower linkage connection pretty much the same and welded that onto the end of the new lever.
Happily, and not without coincidence, the Toyota linkage also is of the sprung type, so with a bit of fettling I removed most of the the mechanism that wasn't necessary but retained the 'sprung' section. I made a few brackets to hold the whole affair in place, widened the aperture in the transmission tunnel slightly to accomodate the new mounting method and hooked it all up. A few adjustments later and I was ready to give it a try.
Result !! I am now much happier with the linkage. The additional spring assistance at the lever itself certainly helps with the selection of gears as it returns quickly to the 3rd/4th plane and is something you can now feel more resistance in. The side/side play has been largely eradicated by the ball & socket system and the shortened throw makes for more direct changes.
Other things left to do are to address any play issues in the middle linkage where the control cables from the gearbox terminate as I think this is where I will find the remainder of the play.
The project is ongoing but its a very good start, I'm chuffed and most people would probably stop here but I'm an inquisitive bugger and not happy until I've addressed/ redesigned anything I can to make it better.
I regret that I have no photos of the various stages of the build as I had leant my camera to my Mum for her holiday! However I will take a piccy of the new system fitted in the next day or so.
Graham
>> Edited by broad on Tuesday 12th July 21:36
>> Edited by broad on Tuesday 12th July 21:38
Not willing to part with calculator figures for the upgrade (I am sure it is nice enough
) and as I hand built an entire linkage for my rally car I felt like having a look to see what I could do to make things a bit better. I haven't finished addressing all of the issues but I did spend the weekend resolving a few things and I thought I'd share my findings thus far with you.
First port of call was a broken Terry clip that is mounted on the gearbox casing underneath one of the shift linkages. The factory fitted one of two types and Simon in the Stores kindly supplied me with both. More common was a 'stiffer' type and it was found that this is what my car had originally fitted - albeit through general metal fatigue it had broken. A fairly swift swap for a new one had the gear lever spring tension restored in the centre/left plane.
However, it occured to me that part of the problem of the undersprung tension at the gear lever end is due largely to the distance between this Terry clip on the gearbox and the gear lever itself, which has no separate spring tension. I wanted to address this issue in the overall plan.
Having removed the gear knob, gaiter and silver trim cover I spent a while studying the existing linkage and noticed that there is an amount of play where the upper pivot linkage connects to the chassis bracket. Upon removal I found that this is not due to wear but due to the play in the threads linking the rod-end to the bracket. As it has to move in 2 planes it cannot be tightened up or you wouldn't get the left/right motion at the gear lever.
My plan therefore was to replace this system with a nice snug ball and socket affair, with further spring assistance at the gear lever end and also reducing the 'throw' of the lever at the same time.
Hunting around I found a linkage from a Toyota that could be modified to suit. It was compact enough for the intended application but the gear lever only extended upwards of the ball & socket and a bit of modding was in order. So having removed the lever from the ball I then removed the material from the bottom of the socket cup to allow for a new lever to pass through.
Next I made the new lever having calculated the relevant pivot point distances to the top and bottom of the lever - and introduced an approximate 20% less throw. This new lever passes through the ball and was welded to keep it firmly in place. I then cut a new M12 thread at the top so that the stock gear knob could be replaced when it was all back together.
I did not want to chop up any of the original lever or its parts so I copied the lower linkage connection pretty much the same and welded that onto the end of the new lever.
Happily, and not without coincidence, the Toyota linkage also is of the sprung type, so with a bit of fettling I removed most of the the mechanism that wasn't necessary but retained the 'sprung' section. I made a few brackets to hold the whole affair in place, widened the aperture in the transmission tunnel slightly to accomodate the new mounting method and hooked it all up. A few adjustments later and I was ready to give it a try.
Result !! I am now much happier with the linkage. The additional spring assistance at the lever itself certainly helps with the selection of gears as it returns quickly to the 3rd/4th plane and is something you can now feel more resistance in. The side/side play has been largely eradicated by the ball & socket system and the shortened throw makes for more direct changes.
Other things left to do are to address any play issues in the middle linkage where the control cables from the gearbox terminate as I think this is where I will find the remainder of the play.
The project is ongoing but its a very good start, I'm chuffed and most people would probably stop here but I'm an inquisitive bugger and not happy until I've addressed/ redesigned anything I can to make it better.
I regret that I have no photos of the various stages of the build as I had leant my camera to my Mum for her holiday! However I will take a piccy of the new system fitted in the next day or so.
Graham
>> Edited by broad on Tuesday 12th July 21:36
>> Edited by broad on Tuesday 12th July 21:38
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