Author Topic: Trans Downshift  (Read 1906 times)

Offline 197

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Trans Downshift
« on: September 20, 2007, 09:08:12 PM »
I got a 73 c20 with a 454 and the stock transmission, If I punch it at 30mph is it supposed down shift out of 3rd into second? Its never down shifted for me. Is there something broke or does something need to be adjusted?
'73 C20 454

Offline 1973c20

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Re: Trans Downshift
« Reply #1 on: September 20, 2007, 09:50:18 PM »
im pretty sure its supposed to downshift. what trans do you have?

Offline 197

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Re: Trans Downshift
« Reply #2 on: September 20, 2007, 09:58:45 PM »
Whatever the stock one is. TH400?

I just looked by my gas pedal and there is some sort of switch.
'73 C20 454

Offline VileZambonie

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Re: Trans Downshift
« Reply #3 on: September 21, 2007, 05:11:28 AM »
The TH400 used a detent solenoid. When the switch on the gas pedal closes 12V should go through the switch to the detent solenoid. The connector is on the LH side of the trans and is a single blade connector
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Offline 197

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Re: Trans Downshift
« Reply #4 on: September 21, 2007, 09:16:08 PM »
The switch thing by the gas pedel is working. And the orange wire goes to the transmission and its plugged in. Is there something in the transmission that could be broke or bad?

And can I shift from drive into 2nd when I need to pass someone?
'73 C20 454

Offline zieg85

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    • 73-87 GM squarebody extended cab and conversions up to 91 R/V series
Re: Trans Downshift
« Reply #5 on: September 21, 2007, 09:36:57 PM »
Sure you can but be careful to not pull it down to 1.  Also if your rear end gear is to low that might also contribute to the problem.  I remember having a 4.56 rear end in my 71 C-20 Longhorn and it was the same way with my TH400. 
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline VileZambonie

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Re: Trans Downshift
« Reply #6 on: September 22, 2007, 01:12:37 PM »
Take a test light to ground and probe the connector to the detent solenoid on the trans. Turn the key on and depress the accelerator pedal. The light should come on.
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                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
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Offline 197

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Re: Trans Downshift
« Reply #7 on: September 22, 2007, 01:29:08 PM »
How does the wire/plug come out? I tried to take it out yesterday but it wouldn't budge.
'73 C20 454