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904 soft 1-2 shift #2571380
10/30/18 12:35 AM
10/30/18 12:35 AM
Joined: Apr 2016
Posts: 184
Memphis,TN
J
J. Hammer Offline OP
member
J. Hammer  Offline OP
member
J

Joined: Apr 2016
Posts: 184
Memphis,TN
I have a 904 that the 1-2 shift seems soft? The shift is quick but much softer than the 2-3 shift. It doesn't seem to slip and has made low 11 second passes in a 3530lb truck with a mild SBM and been street driven about 2000 miles on the street. Its a fwd manual vb unit with a 9.5" converter that stalls around 3800rpm. I plan to hook up a gauge and check line pressure but the headers make it tough. Any ideas or things to check first? Thanks

Re: 904 soft 1-2 shift [Re: J. Hammer] #2571521
10/30/18 11:46 AM
10/30/18 11:46 AM
Joined: Mar 2006
Posts: 9,791
MI, usa
dvw Offline
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dvw  Offline
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Joined: Mar 2006
Posts: 9,791
MI, usa
With a non LBA valve body the only thing that occurs during the 1/2 shift is the forward band applys. Nothing has to be released as the rear sprag overruns. During the 2/3 shift the forward band is released and the forward clutch is applied. For a split instant both components can be applied at the same time . This attempts to lock the trans in 2nd and 3rd at the same time. This feels like a hard shift.
Doug

Re: 904 soft 1-2 shift [Re: J. Hammer] #2571609
10/30/18 02:33 PM
10/30/18 02:33 PM
Joined: Oct 2004
Posts: 2,799
Connecticut
FurryStump Offline
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FurryStump  Offline
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Joined: Oct 2004
Posts: 2,799
Connecticut
Band wear/adjustment? You can adjust that band from the outside of the case


best of 11.39 at 117 mph 1.60 60’. 68 340 S Barracuda Fastback F.A.S.T [IMG]http://i67.tinypic.com/2mnnnnt.jpg[/IMG]
Re: 904 soft 1-2 shift [Re: J. Hammer] #2571665
10/30/18 04:22 PM
10/30/18 04:22 PM
Joined: Dec 2005
Posts: 11,408
Fulton County, PA
C
CMcAllister Offline
Mr. Helpful
CMcAllister  Offline
Mr. Helpful
C

Joined: Dec 2005
Posts: 11,408
Fulton County, PA
Low pressure. Too much spring in the servo. Wrong lever ratio. Accumulator still in the circuit. Forward pattern manual valve bodies are not the best choice.


If the results don't match the theory, change the theory.






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