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As in the lighter spring ? I'm kind of curious how much the spring affects the band release when it is getting pressure fed there on the 2-3 shift . I'm staying with the factory spring on the build I'm doing now

I'd like to know the reasoning why both Sonnax and Superior give these springs in the servo kits
Quote from the Sonnax R servo instructions...

"General Guidelines for Return Spring Selection:
With the various possible combinations of servo apply levers and valve body calibrations, it’s not possible to predict which spring would work best in your application.
For maximum servo apply, start with lightest spring.
If the 2-3 shift has excessive overlap, switch to the return spring with larger wire diameter.
If using the return spring with larger wire diameter and the 2-3 shift has a flare, switch to the spring with smaller diameter wire. "

Sonnax instructions...

https://d2q1ebiag300ih.cloudfront.net/uploads/part/instructions/2935/K36528R-IN.pdf?v=1552585547

So long story short, you can tune the band apply/release with different springs.

More reading from Sonnax.
They have very good tech articles...
This one all about performance servos.
Watch out for the "pin bias effect" !

First, Do No Harm: Things You Should Know about Performance Servos

I know I seem like a Sonnax fan boy, but they do have good products, and their tech guys know their stuff.
Sonnax also puts the info out there for all to see.

Unlike TransGo that seems to have become somewhat secretive about their tech.
TransGo won't even put their shift kit instructions online.
You can only access their tech with a paid (expensive) subscription.

Don't get me wrong, I like TransGo products, I just wish they weren't so paranoid about putting their tech stuff online.
I understand why they are secretive (having spoken to them on the phone) but... oh well...

.
 

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No Greg , I was referring to the removal of half of the reverse piston springs for a "softer" reverse engagement. I am with you on the servo spring , stock spring all the way. I have two "red" springs if anyone needs one.
 

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No Greg , I was referring to the removal of half of the reverse piston springs for a "softer" reverse engagement. I am with you on the servo spring , stock spring all the way. I have two "red" springs if anyone needs one.
Ahh right gotcha... Just looking at the circuit diagrams but going by memory the later 77+ valvebodies had the added checkball and what looks like a .094-.098" feed I think goes to that low/reverse circuit. Perhaps that was to do with softening the reverse apply?
Also the early reverse pistons had the checkball whereas the later didn't . I wonder ?
 

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Reverse checkball....
Early VB no ball. Piston MUST have a ball.

Late VB w/ball. Piston didn’t come with a ball, but you can put a early piston in.
Won’t hurt anything.

Upshot is, must have a ball, either in piston or VB.

Don’t use late piston (no ball) with early VB (again, no ball)

Was told this by old rebuilder.
Never verified the info by looking at oil schematic.
Probably has something to do with when clutch release and oil exhaust.


YMMV
 
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