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A904 1-2 shift valve spring...
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Author:  emsvitil [ Thu Mar 16, 2006 8:59 pm ]
Post subject:  A904 1-2 shift valve spring...
Where can I get a stiffer spring for the 1-2 shift valve?

Current shifts to 2nd at 30mph (about 3000 rpm) vs the 70mph 2-3 shift (about 4000 rpm).

Still have 1bbl, so the 4000 rpm is fine (don't need governor) as I'm running out of breath there anyway, but I'd like to raise the 1-2 shift point with a stiffer spring to get 4000 rpm there to.

Either I'd

1. Buy spring from known source (can't seem to find one anywhere)
2. Improvise.

Improvising would be easy if I knew the original spring's specs (OD, length, spring rate), and if the spring coil binds with the shift valve (or how much can I shim the spring to increase the pressure and raise shift point.

Valve body is in car, so don't have any specs on the spring

Anybody have a valve body lying around?


Thanks
Author:  Dennis Weaver [ Thu Mar 16, 2006 9:25 pm ]
Post subject: 
...shim it. Or simply adjust the kickdown rod.

D/W
Author:  emsvitil [ Thu Mar 16, 2006 9:39 pm ]
Post subject: 
Kickdown is adjusted correctly.


What I don't understand is why don't shift improver kits allow you to change shift rpm when in automatic mode.....................
Author:  bossanova6 [ Fri Mar 17, 2006 2:05 am ]
Post subject: 
Call Pat Blais 206-365-1966
He is the formost expert on 904's and 727's
He is a super nice guy and will answer all of your questions and supply you with any parts you might need.
Author:  Dennis Weaver [ Fri Mar 17, 2006 8:07 am ]
Post subject: 
Quote:
Kickdown is adjusted correctly.
Correctly? Within reason (max travel), kickdown can be adjusted to suit taste. Of course (as you know) this will raise the 2-3 shift also. Picky, picky! ;)

D/W
Author:  emsvitil [ Fri Mar 17, 2006 12:53 pm ]
Post subject: 
The problem is the difference between the 1-2 shift (3000rpm) and the 2-3 shift (4000rpm) at WOT.............

At WOT, the throttle linkage physically bottoms out the throttle valve and without going into all the workings of shifting, you're left with the governor, the 1-2 shift valve spring, and the 2-3 shift valve spring as adjustments.

With the governor you'll raise or lower both the 1-2 shift and 2-3 shift points.

With the 1-2 shift valve spring you only adjust the the 1-2 shift point, and the 2-3 shift valve spring only adjusts the 2-3 shift.


I want the 1-2 shift point to change without affecting the 2-3 shift point, so the spring needs to be changed. (of course changing the governor to raise the 1-2 shift point, and then the 2-3 shift valve spring to lower the 2-3 shift point back down is another way :wink: )


And I don't want to even go into part throttle where various hydraulics pressures are applied to components to vary the shift points..................
Author:  Dennis Weaver [ Fri Mar 17, 2006 1:05 pm ]
Post subject: 
...yeah, I got all that. That's why I said you were picky! :P

I think if it's shifting 1-2 WOT @ 3000 RPM and your kickdown is adjusted for max travel, you have some kind of valve body malfunction, either an internal leak or a weak spring. Perhaps even renewing the 1-2 shift spring would help.

D/W
Author:  emsvitil [ Fri Mar 17, 2006 5:19 pm ]
Post subject: 
Only 17000 miles on tranny (and car btw), so it probably was new that way.

It is within spec according to the manual as the shift points at WOT are:

1-2 28-45mph. (2800-4500rpm)
2-3 62-76mph. (3500-4500rpm)


But those are awfully large ranges for manufactures tolerance.



And yes, I am picky. 8)
Author:  emsvitil [ Fri Mar 17, 2006 5:23 pm ]
Post subject: 
I'll also throw out that adjusting the shift point(s) rpm will have MUCH more of an effect on accleration than the shift quality which is what the so-called shift-improvers only do....

So it shouldn't be such a pain-in-the-neck to change the shift points.........
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