is my modulator valve bad on powerglide - Chevelle Tech
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Transmission & Driveline Transmissions and Differentials

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  #1  
Old Jun 7th, 07, 11:27 AM
bhawk bhawk is offline
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Default is my modulator valve bad on powerglide

I just got to drive my 65 chevelle after a 6 year restoration project. When I bought it in 2000, I drove it a bit and the 2 speed powerglide, stock and original to the car, seemed to shift fine from 1-2.
However, it never turned a wheel for the last 6 years until this week. I drove it and find the following:
- it shifts very quickly out of 1 into 2, say if I turn out of my driveway onto the street I only go about 20 feet before it shifts into 2, seems way too soon.
- secondly, the shift from 1-2 seems harsh, almost a jerk, even if I go real easy on the gas pedal.
- if I accelerate from a standing stop using a bit of gas pedal, it will shift out of 1 at a higher speed, but then I get a real harsh shift, almost a bang into 2.
Could this be a bad modulator valve? this would be about the only thing I can do myself. I did change the oil and filter before taking it for the first cruise and the fluid is up to correct level. Any ideas, thanks.
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  #2  
Old Jun 7th, 07, 1:40 PM
rbwjr325 rbwjr325 is offline
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Default Re: is my modulator valve bad on powerglide

Take a look and make sure every thing is still conected to trans and at carb linkage.After that long I would change mod. valve. See if theres any trans. fluid in vac. line at mod. valve.If there is ,change it. They used to sell an adjustable valve.
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Old Jun 8th, 07, 9:14 AM
bhawk bhawk is offline
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Default Re: is my modulator valve bad on powerglide

thanks for the advice. I am going to check out the vacuum at the line near the modulator. If it is not too expensive I will probably replace it and see if it gets better.
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Old Jun 8th, 07, 5:07 PM
LeoP LeoP is offline
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Default Re: is my modulator valve bad on powerglide

Since it sat for so long, I would drive it to get all the hydraulic systems fully functional, sometimes sitting makes the tranny act stiff for awhile.
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  #5  
Old Jun 8th, 07, 11:30 PM
bhawk bhawk is offline
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Default Re: is my modulator valve bad on powerglide

thanks Leo, that also is a good idea. I am going to licence it tomorrow for full cruising. Then I will put a couple hundred miles on it before I do anything. I inquired today at a parts store and the modulator is 44 bucks. Not too bad, so I may put it in later and report back.
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Old Jun 9th, 07, 2:16 PM
Schurkey Schurkey is offline
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Default Re: is my modulator valve bad on powerglide

44 dollars for a modulator is insane even with the exchange rate.

http://store.summitracing.com/partde...5&autoview=sku

Generally, when a modulator goes bad, the shifts will be very late--high RPM--and very hard. (until the fluid is all sucked out, then it just won't go into gear very well; and will have lots of slippage.) Early shifts don't indicate a bad modulator.
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Old Jun 10th, 07, 12:10 AM
Oldani Motorsports Oldani Motorsports is offline
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Default Re: is my modulator valve bad on powerglide

Check the detent downshift link adjustment first. And modulators are less than $10, ouch.
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Old Jun 25th, 07, 10:56 AM
baloo28 baloo28 is offline
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Default Re: is my modulator valve bad on powerglide

Generally, when a modulator goes bad, the shifts will be very late--high RPM--and very hard. (until the fluid is all sucked out, then it just won't go into gear very well; and will have lots of slippage.) Early shifts don't indicate a bad modulator.[/QUOTE]

Mine is having the same problem, but my modulator isn't hooked up at all. I have the intake plugged and just loose at the modulator. What else could it be?
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  #9  
Old Jun 25th, 07, 10:57 AM
baloo28 baloo28 is offline
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Default Re: is my modulator valve bad on powerglide

Quote:
Originally Posted by Oldani Motorsports View Post
Check the detent downshift link adjustment first. And modulators are less than $10, ouch.
How is that performed? How much free play is acceptable from the ball to the end of the linkage?
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