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Throttle Cable Play, Lurch into Second |
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broken 
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Joined: Nov/21/2012 Location: Canada Status: Offline Points: 100 |
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 Topic: Throttle Cable Play, Lurch into SecondPosted: Apr/14/2014 at 6:04pm |
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Changed out a snapped throttle cable on my 304 automatic (thread here). Throttle seems nice and smooth, better control than previously, it's also taut. Everything seems in order and feels good except that the engine seems to over rev in 1st and lurch into 2nd unless I'm aggressive on the throttle (which is sadly not enough in the city).
I've read this can happen due to throttle cable play, does it need to be tighter, looser, perhaps a stronger return spring? I've not had much transmission experience. Cheers.
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1975 AMC Hornet 304, Holley 1460, Offenhauser 360
1975 Honda CB400F Super Sport |
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FuzzFace2
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Joined: Jul/05/2007 Location: Angier, N.C. Status: Offline Points: 10356 |
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Posted: Apr/14/2014 at 9:27pm |
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The TSM should have how to adjust it.
As a guess it needs more slack. IIRC if too tight the shift from 1 to 2 will be at a higher RPM and can shift hard into 2nd.
Dave ----
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TSM = Technical Service Manual
75 Gremlin X v8 for sale 70 Javelin 360/auto drag car 70 Javelin 360/T5 Street car |
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broken
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Joined: Nov/21/2012 Location: Canada Status: Offline Points: 100 |
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Posted: Apr/15/2014 at 8:16am |
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That definitely seems to be what's happening. I'll check the TSM and giver some slack.
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1975 AMC Hornet 304, Holley 1460, Offenhauser 360
1975 Honda CB400F Super Sport |
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broken
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Joined: Nov/21/2012 Location: Canada Status: Offline Points: 100 |
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Posted: Apr/23/2014 at 9:50am |
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I tried giving the throttle cable more play but it doesn't seem to have solved the issue. Still over-rev'ing and lurching into second. I topped up the transmission fluid.
I'm green to transmission issues, as I understand it the kickdown linkage below the throttle cable is responsible for downshifting, and vacuum pressure is responsible for upshifting, is it only vacuum pressure? Does anyone have a good source outlining the workings of these particular automatic transmissions, or some clear troubleshooting steps? Cheers.
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1975 AMC Hornet 304, Holley 1460, Offenhauser 360
1975 Honda CB400F Super Sport |
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FuzzFace2
AMC Addicted
Joined: Jul/05/2007 Location: Angier, N.C. Status: Offline Points: 10356 |
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Posted: Apr/23/2014 at 11:34am |
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I should have said it’s not the throttle that needs more play but the kick down linkage to the trany. It is not vacuum that controls the shifting, no vac. going to the trany, but the linkage. The linkage tells the trany how much ATF psi should be applied to the system. You running the stock carb or aftermarket like a Holley? The TSM should have how to adjust the kick down linkage. But if you look at the throttle & the kick down linkage you should be able to see how it works. As you give it throttle I think it pulls on the kick down linkage so you need to add more play to the kick down linkage. It may work the other way but is easy to tell when you look it over. Before you make adjustments mark the linkage so you know where you started then make a little adjustment say ¼” to start, then take for a drive to see if it changes. If better but not right move it again & drive till you get it right. If you cant get it post up a picture of the carb & linkage and we will see what we can do for you then. Dave ---- |
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TSM = Technical Service Manual
75 Gremlin X v8 for sale 70 Javelin 360/auto drag car 70 Javelin 360/T5 Street car |
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broken
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Joined: Nov/21/2012 Location: Canada Status: Offline Points: 100 |
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Posted: Apr/23/2014 at 5:31pm |
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Thanks Dave, I shortened the kickdown linkage (1, 2 and 3 in the image) so that when the throttle is closed the transmission rod that it actuates (3 in the image) is forward (towards the front of the car) and the throttle pin is at the end of slotted kickdown bracket (1 in image). When I re-attach the spring this pulls it to leave about 1/2" of play as seen forward of 1 in the image.
 I think it may be better but there's still some lurch into second. Should the transmission rod, 3 in the image, be all the way forward or back when the throttle is closed? I threw some other numbers in the image in case they come in handy. Update: I looked at an older photo of this linkage, before the replacement throttle and the spring that is now connecting 1 and 2 used to be connecting 2 and 5 instead to keep the kickdown linkage taught against the throttle pin -- that doesn't seem like what should be happening, but maybe I'll try it.
Edited by broken - Apr/24/2014 at 9:11am |
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1975 AMC Hornet 304, Holley 1460, Offenhauser 360
1975 Honda CB400F Super Sport |
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broken
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Joined: Nov/21/2012 Location: Canada Status: Offline Points: 100 |
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Posted: Apr/24/2014 at 8:00am |
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I think moving the spring to pull the kickdown linkage back towards the firewall did the trick. It eliminates the play at the forward end of the kickdown slot. I wasn't the one who move that spring to the wrong place, can't trust anyone I guess :)
For anyone else having kickdown troubles, there's another great thread that explains its function and operation, |
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1975 AMC Hornet 304, Holley 1460, Offenhauser 360
1975 Honda CB400F Super Sport |
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FuzzFace2
AMC Addicted
Joined: Jul/05/2007 Location: Angier, N.C. Status: Offline Points: 10356 |
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Posted: Apr/24/2014 at 9:07am |
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Good to hear you got it working right.
Yes on the spring going 2 to 5 and NOT 1 to 2. With the spring at 1-2 the kick down rod was moving with the throttle, just like if you took the play out at #1 by adjusting at #2 bolt and that is not good.
Did that make sence? I know with the spring in 2-5 the rod is pulled to the throttle pin but the rod is pushed back telling the trany to use less PSI to the system but that is the way it works.
If you made adjsutment to the rod at #2 bolt before you got the spring on right you may need to make adjustments to get it to shift right.
BTW I have a shift kit in my 75 Gremlin and had to adjust that rod. Normal throttle and it shifts like stock, get on it a little and it shifts hard, foot to floor it will chirp the tires going into 2nd gear.
Dave ----
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TSM = Technical Service Manual
75 Gremlin X v8 for sale 70 Javelin 360/auto drag car 70 Javelin 360/T5 Street car |
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PHAT69AMX
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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Posted: Apr/26/2014 at 4:16pm |
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Guess no harm in posting images here in this thread that are shown in referenced external thread
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