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Discussion Starter #1
I've had the truck apart for 6 or 7 years and finally got the 460 back together for it. Installed a single plane with a holley 750 vacuum secondaries. Of course the kickdown rod wouldn't fit, so I went without for a bit. I adjusted the modulator in a bit because when driving it would shift at 3800rpm or so.

Fast forward to this weekend and I installed the kickdown cable. Under half throttle it'll shift fine 1-2 very firm. Under wot I've had the truck spinning probably 5000rpm or so (hard to tell digital tach is slower at keeping up I guess) as soon as I lift a bit it'll shift into 2nd.

I then turned the modulator back out a half turn and it seems it made no difference under wot. I also loosened the kickdown cable thinking it may have been adjusted wrong.

Before I took the truck apart many years ago it was fine.

I've been searching the last 2 days and came across more than a couple with similar issues but didn't see any resolutions.
 

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Maybe try backing out the kick-down screw that is on the Holley kick-down linkage. Basically requires the throttle to be opened further to actuate the trans kick-down rod/cable.
 

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so you are having upshift issues from 1st to 2nd? I thought the kick down only triggered a down shift, usually from 3rd to 2nd.
Can you manually upshift from 1st to 2nd under WOT? That should over ride the vacuum modulator.
 

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Discussion Starter #6
Yeah it'll upshift manually fine. I haven't had a chance to mess with it anymore as I've had a lot of hours at work this week. Tuesday I should have some time to check it out.
 

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Discussion Starter #7
Not sure what changed. Drove the truck more than just around the block and now the upshot is working. Though I would like it to shift a bit sooner but seems to be ok now. Not sure what was up.
 

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Could be the motor settled a bit ? Giving a different vacuum signal. You do have a good full manifold vacuum source ? Where is the modulator set at ? You could check how much preload the modulator has , then possibly use a shorter pin. If it is a push in modulator that is easy to do, loosen the bracket and feel how much the modulator pops out .

Good to see it is working. That's funny usually everyone wants later shifts , this one is the opposite.
 
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