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 Post subject: 1st gear gone
 Post Posted: Fri Apr 08, 2011 1:22 pm 
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Hi everyone. The Powerglide trans, and the transbrake worked fine up to the line, launched in 1st, shifted into second. At the end of the run I shifted from 2nd into 1st at about 5mph, and there was no 1st gear, felt like nutural. No reverse either. I put it in 2nd and drove it to the trailer. I was hoping it was the linkage but it is not. Any idea what is wrong? I bought it used recently and am nor very familiar with it. Are there PG setups where you should not downshift while moving? Thanks.


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 Post subject: Re: 1st gear gone
 Post Posted: Fri Apr 08, 2011 1:54 pm 
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The low band servo has to activate in order to lock the high gear drum to make low gear work. You can connect a pressure gauge to the servo to see if you have line pressure there. It's the small 1/8 pipe plug on the triangular shaped 3 bolt plate on the passenger side of the tranny. You'll need a gauge that will up to 300psig as some of those things operate up around 275psig and you might also need a hose to make that connection around the header. Check line pressure there with the engine running in low gear.

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 Post subject: Re: 1st gear gone
 Post Posted: Fri Apr 08, 2011 2:42 pm 
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Ken0069 wrote:
The low band servo has to activate in order to lock the high gear drum to make low gear work. You can connect a pressure gauge to the servo to see if you have line pressure there. It's the small 1/8 pipe plug on the triangular shaped 3 bolt plate on the passenger side of the tranny. You'll need a gauge that will up to 300psig as some of those things operate up around 275psig and you might also need a hose to make that connection around the header. Check line pressure there with the engine running in low gear.


That was way helpful Ken. Thanks. I realize I am a little ignorant here but what can make the low band servo not activate?


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 Post subject: Re: 1st gear gone
 Post Posted: Fri Apr 08, 2011 4:46 pm 
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No pressure..... =;

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running E85
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 Post subject: Re: 1st gear gone
 Post Posted: Fri Apr 08, 2011 6:22 pm 
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fasthappy wrote:
That was way helpful Ken. Thanks. I realize I am a little ignorant here but what can make the low band servo not activate?


Humm, did it make any funny noises at all in low gear or reverse, ie, sound like something was broke?

Did it "creep" when the transbrake button was pressed, ie, try to go forward before it locked down? Yes indicates that the low band adjustment might have been off which "might" lead to the following.

It could be as simple as the yoke that fits between the servo and the low band has come loose and fallen into the pan. Seen that a couple of times and is usually caused by it being out of adjustment.

When it's in low gear there is pressure on the outside of the servo piston pushing it in and clamping the band to the high gear drum. When the gear change is made hydraulic pressure is applied to the other side of that servo and also the high gear clutch pack at the same time and when pressure starts to build and applies the high gear clutches, it also starts to push the servo piston away via a LARGE spring inside the piston. Once it's in high gear, hydraulic pressure across the servo is "balanced" or neutral and the spring releases the low band.

Then again the pinion in the center of the planetary could have broken and that could cause no low and reverse. If you got no gauge and stuff you might want to jack it up and pull the pan off to see if anything has fallen off. That won't cost you any money and won't take very long either.

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 Post subject: Re: 1st gear gone
 Post Posted: Fri Apr 08, 2011 9:57 pm 
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Thank you Barry and Ken. I appriciate the helpful advice. I'm going to get started on it tonight.
-Ty


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