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Old 07-07-2013, 02:54 PM   #1
InsouciantSoul
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1981 Silverado not switching into third gear.

Took a drive home from my ladies house this morning, and noticed trouble getting into third gear. It would rev louder and louder, if i let off the gas a bit and revved again, the truck would suddenly switch into third and pull forward quickly. After 2 times of that, I couldn't get the truck into third. Just revving loudly at 2nd gear.

When I first started the truck i heard a few loud bangs or clanking noises when in idle. Couldn't tell where it was coming from but sounded like it was from the rear end, maybe just the exhaust.

Where to start to diagnose the problem?
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Old 07-07-2013, 03:18 PM   #2
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Re: 1981 Silverado not switching into third gear.

Nevermind - Fixed. Sorry for useless thread. The vacuum line was unplugged from the transmission. I didn't know that's how it changed gears.
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Old 07-07-2013, 03:18 PM   #3
INSIDIOUS '86
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Re: 1981 Silverado not switching into third gear.

Is this a th350 or 700r4?
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Old 07-07-2013, 03:23 PM   #4
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Re: 1981 Silverado not switching into third gear.

Quote:
Originally Posted by InsouciantSoul View Post
Nevermind - Fixed. Sorry for useless thread. The vacuum line was unplugged from the transmission. I didn't know that's how it changed gears.
It's a kickdown device. But glad to know it was an easy fix
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Old 07-07-2013, 05:07 PM   #5
kalbert
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Re: 1981 Silverado not switching into third gear.

Not exactly a kickdown, its a pressure regulator that uses engine vacuum to sense load. Governor pressure is applied to one side of the valves fighting for an up shift, modulator pressure is applied to the other side fighting for a down shift. This is obviously an over simplification but you get the idea. The kick down is a mechanical link that actuates a valve directly and forces a down shift at or near wot.
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