79 C6 detent and band questions... - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-08-2012, 07:37 PM
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79 C6 detent and band questions...

I've tried other forums, I get the best answers here... So here I go.


I just rebuilt my C6. The 1-2 shift is a tad soft, I was thinking of just tightening the band adjuster a little (like 1/4 turn maybe less). I did originally use a tq wrench but I have poor luck (new to special tools).


How far does the detent lever (on trans) need to push the valve to kickdown? Does it start as soon as the valve opens or at the end? Reason is I never had good kickdown and now I have none. With throttle pressed the kickdown still isn't totally open (maybe between 1/4-1/8 turn left to go with gas pedal to floor). I couldn't tell where WOT is to adjust it using manuals instructions.. So I'm gonna do it by feel.



Greg

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Old 01-08-2012, 08:29 PM
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Guess I really wanna know when the detent kicks down... Does the valve have to be all the way pressed to kickdown or does it kickdown as soon as it moves?


Greg
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Old 01-16-2012, 05:11 PM
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Not sure if you got an answer yet;

soft 1 - 2 shift is a control of multiple things,

band adjustment will not help a soft shift if the adjustment is close to correct.

Shift firmness of 1 - 2 shift is controlled by : servo size, the band lever fulcrum angle, the accumulator spring in the valve body and the main line pressure.

There are several different size servo pistons for the C6

The band lever is replaceable and there are several different levers with higher apply angles for more holding power on the band.

Main line pressure; higher is a firmer shift.

1 - 2 shift accumulator in the valve body usually has broken OEM springs in an old C6 unit. Many shift mod kits block this accumulator in place or provide stiffer springs for the accumulator.

The detent lever affects the shifts at different apply of the throttle depending on the road speed of the vehicle , main line pressure, and level of vacuum the modulator sees at that moment. They all work together to affect shift timing or down shifts.

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Old 01-17-2012, 02:33 AM
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So the 1-2 shift sucks but the 2-3 shift is nice and firm. It doesn't seem to get more firm with more gas though for any shift.. It's hard to tell though because it's snowy and icy out so I couldn't just romp on it. The kickdown bolt is too short next to the carb, I'll replace that.

So I used a N code servo and a A code lever. That was stock, the servo is new and the lever is original.

I replaced the accumulator spring with the one in the SK6 kit. I had to measure with a dial caliper to use the correct spring. There was a new set of springs for the pressure booster valve too. I used the recommended single large spring for the group of springs (there where 3 originally IIRC) It also had me drill a hole larger in the seperator plate, my broader instructions said to do the same but then for the all out setup they recommended not enlarging the hole for the firmest shifts. Not REALLY sure what that was suppose to do..

Now for line pressure... I replaced the front pump with a rebuilt one. I did forget to install the gasket on the filter before the valve body.. The DVD I have said it isn't needed but somewhere online I read that it could affect line pressure. What one is true?

I had to use thicker steels in one of my drums (cant remember what one) to tighten the clearance but afterwards they both checked out nice. My final endplay was on the large in but it still seemed within specs.
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Old 01-17-2012, 05:27 AM
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Quote:
Originally Posted by ekacpuc
So the 1-2 shift sucks but the 2-3 shift is nice and firm. It doesn't seem to get more firm with more gas though for any shift.. It's hard to tell though because it's snowy and icy out so I couldn't just romp on it. The kickdown bolt is too short next to the carb, I'll replace that.

So I used a N code servo and a A code lever. That was stock, the servo is new and the lever is original.

explains a bit on shift quality .. the N servo is the small one.

Lever "A" is on low side for fulcrum apply ... "E" lever is better choice

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