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Kickdown Question
https://slantsix.org/forum/viewtopic.php?f=20&t=66576		 Page 1 of 1
Author:  scott s [ Mon May 09, 2022 7:50 am ]
Post subject:  Kickdown Question
Kick down question:
I had to make some pretty big adjustments on my throttle pedal and kick down linkage when swapping carbs. The P.O. had the wrong carb hooked up and had it all out of whack. You can see the newly exposed threads in the pics.
Car runs great and goes through the gears nicely now, but doesn't kick down in passing gear.
I see HOW to adjust the kick down, but I can't access it in my garage.
Will I damage anything if I drive it like this until I get it to a shop with a lift?

To clarify: it shifts fine up and down through the gears. Shifts are soft and normal/not harsh or clunky.
Under light throttle, hits 2nd around 15mph, 3rd around 22-25mph.
Under harder acceleration, it holds the gears a little longer but still shifts great.
What it DOES NOT DO is drop from 3rd to 2nd if I punch it, like trying to pass a car.

Attachment:
lengthened kickdown.jpg
lengthened kickdown.jpg [ 174.68 KiB | Viewed 1328 times ]

Attachment:
pedal lengthened.jpg
pedal lengthened.jpg [ 231.99 KiB | Viewed 1328 times ]
Author:  scott s [ Mon May 09, 2022 11:36 am ]
Post subject:  Re: Kickdown Question
At full throttle, the carb butterfly is 100% open. I disconnect the TV rod and can push it down. I gave it another turn out and took it for a test drive.

I also found this information:
In 1968, part-throttle downshift functionality was added to A-904 transmissions used with six-cylinder engines. This feature permitted the transmission to shift from third to second gear in response to moderate accelerator pressure. Previously, an automatic 3-2 downshift occurred only if the driver pushed the accelerator to the floor. This change was made to maintain acceptable in-town performance with taller final-drive ratios in the rear axle — 2.76:1 rear axle gears were being furnished in applications previously equipped with 2.93:1 or 3.23:1 gearsets. Part-throttle downshift functionality was extended to V8 A-904s in 1969, and to most A-727 transmissions in 1970 to 1971.

I wasn't aware that I had to completely mat it. Knowing that, it DOES kick down, but only holds 2nd gear for a couple of seconds before going back to 3rd. Does that mean I need to keep extending the TV rod?
How long should it hold a passing gear before shifting back to 3rd?
Author:  Greg Ondayko [ Tue May 10, 2022 11:36 am ]
Post subject:  Re: Kickdown Question
I think It's a matter of personal Preference..
I know there are some years where there is a part throttle kickdown valve - other years where there is not.

I always futz with my kickdowns to get them to match the engine output, my driving style, rear gear ratio, (and terrain 'round these parts).
Stock 1980 aspen with 225 1 bbl / 2.76 and a tired slant??
Might need a lot of tv input to make it happy round here.

Fire breathing 440 with 4.56's on flat land - Maybe not as much...


You'll find it when it seems right and it's not hunting for that gear after a good smashin' of the right pedal.

Greg
Author:  Dart270 [ Tue May 10, 2022 12:20 pm ]
Post subject:  Re: Kickdown Question
I would lengthen the kickdown threaded rod another 1/8" and drive it. If not kicking down, do another 1/8" and so on.

You can also/instead disconnect the ball end for that linkage, push the rod all way down until the KD lever hits the stop, then push down and hold the carb/throttle rod so the throttle is wide open, then lengthen the KD rod so the KD lever is all the way back. This will give maximum KD. Drive and see how you like it. If too harsh, back off in 1/8" increments of the kickdown threaded rod.

Hope this helps,

Lou
Author:  SlantSixDan [ Tue May 10, 2022 10:36 pm ]
Post subject:  Re: Kickdown Question
Make sure your transmission bands (including the kickdown band) are adjusted correctly; given the neglect you've been fixing elsewhere on the car, it seems likely they aren't. Go through and adjust the entire throttle and kickdown linkage—including the accelerator pedal angle. Do it as prescribed in the service manual, not by guess and at random.
Author:  Dart270 [ Wed May 11, 2022 6:44 am ]
Post subject:  Re: Kickdown Question
Agreed on the band adjustments too.

Lou
Author:  scott s [ Wed May 11, 2022 4:51 pm ]
Post subject:  Re: Kickdown Question
Dart270 wrote:
Agreed on the band adjustments too.

Lou

SlantSixDan wrote:
Make sure your transmission bands (including the kickdown band) are adjusted correctly; given the neglect you've been fixing elsewhere on the car, it seems likely they aren't. Go through and adjust the entire throttle and kickdown linkage—including the accelerator pedal angle. Do it as prescribed in the service manual, not by guess and at random.


Is that something I can do at home?

I followed the FSM instructions for adjusting the pedal, the lower adjustment on the TV rod, and the throttle. It's all much much better and I actually have a passing gear now. I think I can keep sneaking up on the TV rod adjustment until I get it completely dialed in.
Author:  SlantSixDan [ Wed May 11, 2022 6:41 pm ]
Post subject:  Re: Kickdown Question
Band adjustment isn't as easy as kickdown linkage adjustment, but it's not awfully hard, either. Study the service manual. While you are paying attention to the transmission, this is a good time to give it a fluid and filter change. Unlike many other automatics, this one can be drained fully, including the torque converter (there's a drain plug on the converter itself). Make certain you get the correct 1964-'65 filter, which has three screw holes and two round ports, not just one (the '66-up filter has just one). Use a reputable major brand of Dexron-VI fluid.
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