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| Kickdown linkage driving me crazy https://slantsix.org/forum/viewtopic.php?t=26121 |
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| Author: | ESP47 [ Tue Dec 04, 2007 4:56 pm ] |
| Post subject: | Kickdown linkage driving me crazy |
Ok so I put a NOS Carter BBD on (runs and idles great now) but the kickdown linkage stopped working correctly. Before with the remanufactured Carter, I could hardly even feel the thing shift and I got a slight kick down when I'd step on the gas at around 40mph or so. Everything worked the way it should. Now with this new carb, the tranny shifts to 2nd and then immediately to 3rd. So basically from a dead stop I'll hit the gas pretty hard and it shifts to 2nd around 20mph or so and then 3rd at about 25mph. The only thing I can assume, since I didn't touch anything other than the carb, is that the kickdown linkage needs to be adjusted. Maybe because the NOS throttle shaft turns differently than the old carb's shaft?? Now im a little confused with the kickdown. I got under the car and moved the rod all the way forward towards the front of the car. I only had to move it up about 1/4" from the original setting to move it all the way towards the front. Took it for a test drive and it still just shifted right into 2nd and 3rd without more than a second to a second and a half in between shifts. So I backed the adjustment off and moved it an inch towards the back of the car. Tried it again and this time it shifted the same, it just shifted a lot harder this time. I know you can't really tell me what the setting for my car will be, but can anyone give me some details on exactly how it works and what moving it forward or backwards should do to the shifting? Thanks. |
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| Author: | SlantSixDan [ Tue Dec 04, 2007 5:11 pm ] |
| Post subject: | |
Did you go from a 1bbl to a 2bbl? Or from an old 2bbl to a new 2bbl? If you went from a 1bbl to a 2bbl, did you install the complete 2bbl style kickdown linkage? |
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| Author: | ESP47 [ Tue Dec 04, 2007 5:28 pm ] |
| Post subject: | |
I went from an old 2bbl to a new 2bbl. It shifted fine with the old carb. I didn't change anything that could have affected the linkage other than just swapping the carbs. |
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| Author: | SlantSixDan [ Tue Dec 04, 2007 5:49 pm ] |
| Post subject: | |
Your transmission's short-shifting behaviour sounds like one of two problems: 2) The kickdown adjustment isn't set properly. It can be pretty confusing when you're under the car actually making the adjustment; it's really easy to get crossed up and move the slider box the wrong direction. And even if you didn't touch the adjustment, simple things like a change in carburetor base gasket thickness can throw off the adjustment. Try loosening the clamp bolt and moving the slider box one inch to the rear, relative to the kickdown rod coming down from the carb, then tightening the clamp bolt. If this makes a significant difference (your kickdown operation comes back, and the 1-2 and 2-3 shifts occur at noticeably higher road speeds), then all you have to do is fine-tune the position of the slider box on the kickdown rod. Moving it rearward (towards the lower end of the rod) makes the 1-2 and 2-3 shifts later and harder, and the kickdown earlier. Moving it forward (towards the front of the car) makes the 1-2 and 2-3 occur earlier and softer, and the kickdown later. 2) the throttle pressure valve fell out of the grip of the trans throttle pressure ("kickdown") lever. This can occur if all of the preload is taken off the trans kickdown lever, even for a moment, and the retainer clip for the throttle pressure valve in the trans is missing. Drop the pan and operate the throttle through its full travel while watching the works inside the trans housing from underneath. I suspect you will not see the throttle valve being operated by the kickdown lever. |
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| Author: | Sam Powell [ Wed Dec 05, 2007 5:39 am ] |
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That rod modulates line pressure as well as shift timing. If it is missing, your clutches do not have enough pressure on them at shift, and you will wear them out faster. I suspect you may be able to get it working right by simply moving the kick down t lever which come out of the trans back an inch or so relative to the carb linkage. There is a minimum shift point for 1st to 2nd in the factory shop manual which will guide you in its adjustment. Sam |
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| Author: | ESP47 [ Sat Dec 08, 2007 4:30 pm ] |
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Thanks for the tips guys. Looks like I got it fixed. What I did was move the linkage rod as far toward the front of the car as it would go. So the bolt in that nut is just barely hanging on to the end of the linkage. Then I noticed my throttle cable wasn't pulling the throttle shaft as far back as it could go. So I adjusted that a little tighter. Now the cable pulls the shaft all the way back and the kickdown pushes down far enough to engage. Before this, with the kickdown moved back towards the rear an inch, I was in 3rd gear at 20mph with no kickdown at all. Now it waits until 40-50 to get into 3rd and I can feel the kickdown when I stomp on it. It's amazing how such a small change can have such a huge effect on the way the car runs. |
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