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  #1  
Old 08-12-2009, 09:29 PM
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Ham Shanker
 
Join Date: May 2008
Location: Baltimore, MD
Posts: 2,544
Is my transmission slipping?

ALDA removed, full boost @ 1500~1700rpm; theoretically giving me full torque way earlier than the initial design.

Starting from a stop, if I give more than 25% pedal I stop accelerating and get a THUMP-THUMP-THUMP-THUMP that shakes the car and is OBVIOUSLY coming from the transmission. It stops when I let off, and it shifts faster up into 3rd than I would prefer.

Only does it on the 1-2 shift.
In any other gear, it lugs down the way every other 617 does when started in too high of a gear.

Vaccum to the transmission changes nothing, Bowen cable adjustment only changes how soon it attempts to go from 1-2; the thumping still occurs.


Any suggestions?

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Old 08-12-2009, 09:37 PM
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Join Date: Jan 2006
Location: Northeast Indiana
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How solid were the shifts before the ALDA adjustment?

Sounds like a band slipping, increase the modulator pressure and see if it solves the problem before you destroy the band. Or if you can do the operating pressure test, that would be a better start.
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Old 08-12-2009, 09:52 PM
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Ham Shanker
 
Join Date: May 2008
Location: Baltimore, MD
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Adjusting the vaccuum to the transmission doesn't change how it shifts.

Is there another modulator I should be playing with?
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  #4  
Old 08-12-2009, 09:58 PM
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Yes, the hydraulic pressure modulator on the side of the transmission. If you don't have a manual, do a search on modulator and transmission here and in the tech forum (not sure where they are).

The 1-2 shift is a brake band, and without enough hydraulic pressure to engage it completely it will slip as you describe. Could also be worn-out, but if so the transmission has to come apart anyway, might as well try the modulator adjustment (operating pressure increase) first.
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  #5  
Old 08-13-2009, 08:14 AM
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Ham Shanker
 
Join Date: May 2008
Location: Baltimore, MD
Posts: 2,544
Found the DIY:
http://www.peachparts.com/Wikka/Trans722VacMod
I'll give it a go tonight!

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