Shifting MPH

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Sep 28, 2012 | 04:57 PM

MoonpieH2O

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Joined: Apr 2010

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From: Pittsburg, Tx

Shifting MPH

I have a 1976 F-150 with the 390/C6 combo. I installed a new Vacuum Modulator Valve without adjusting it. My Question is at what speed does the tranny shift from 1st to 2nd, and 2nd to 3rd. Just looking for a target number before I start adjusting. Right now it pretty much goes through all three gears by about 34mph.

Thanks

Sep 28, 2012 | 06:51 PM

devino246

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From: Lynchburg, VA

There's no magic number. The purpose of the modulator is to detect manifold vacuum and adjust shift points to suit. If you're accelerating lightly, being in third by 35 is normal. That adjustment is really only used to fine tune the shifts.

Sep 28, 2012 | 09:04 PM

VocaTexas

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That sounds about right. My '79 with a 351M, under fairly hard acceleration shifts at around 20 and 40, but under light throttle is something like 15 and 30.