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C6 Doesn't like upshifting???

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Old Jul 1, 2005 | 09:51 PM
  #1  
Almost_A_Merc's Avatar
Almost_A_Merc
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From: Rapid City SD
C6 Doesn't like upshifting???

Well I took my truck on it's mayden voage, first time on a highway since the rebuilt 390, Disc Brake Conversion, etc etc... lots of little stuff. Anyhow, 2 years ago the Trans worked fine. Now if I put the tranny into Drive it will NOT shift up, no matter how fast I go. If I shift it manually into 2nd, it will shift, and shifting into Drive (trying to get into 3rd) it wont do it. I tried a few things and finally I found if I let off the gas and put it into D from 2nd it would sometimes shift. Currently I do not have the kickdown linkage connected or the vacuum line.. this may be the cause, however I thought it would upshift with these disconnected, just not downshift.

Any ideas?

Thanks
David
 
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Old Jul 2, 2005 | 12:41 AM
  #2  
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docholiday72tx
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From: waco
Hey David....it's definately the vacume line. The passing gear does not have to be hooked up at all. MIne hasn't been in 2 years, but that vacume line has to be hooked up.
Doc
 
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Old Jul 2, 2005 | 01:21 AM
  #3  
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you need the shift modulator hooked up.
 
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Old Jul 2, 2005 | 12:50 PM
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fling
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vacume

with your vacume line disconnected, your tranny thinks you running full throttle the whole time, therefore increasing the shift points.
 
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Old Jul 2, 2005 | 01:36 PM
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Yup, it's the vac line. I never even had the linkage on my truck for the kickdown, it would still shift fine. IIRC, the c6 is just about the only tranny that can handle running without throttle lever input, everything else uses that to control most of the shift parameters.
 
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Old Jul 4, 2005 | 09:07 AM
  #6  
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kristoph30
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From: grafton usa
I had the same issue. But I had everything hooked up. Turned out a mud wasp had built a nest in the steel vac line!
 
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Old Jul 5, 2005 | 09:56 PM
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From: Rapid City SD
Well, Ya'll were exactly RIGHT! Thanks for your help! I'm really enjoying driving the truck!

God Bless
David S.
 
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Old Jul 6, 2005 | 12:45 AM
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rubber band maybe

I had that problem once. Started at a national transmission chain - they wanted $200 just to diagnose, and said the whole transmission was shot. Then I took it to a local guy and he replaced some kind of band (R & R band?) and didn't even charge me anything, and that fixed the problem.
 
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