C6 kickdown

[vozaday]

Ok, I've been doing some reading but need a schooling on the kickdown cable.  When I bought my car it did not have one.  Now the transmission does downshift if I step on it and it seems to have a vacuum line going to the transmission.  So I figured that was the kickdown all along.  But reading some of the threads on here getting ready to install the 1406 carb I see most people needed an extension.  It was through these pictures that I now know what a kickdown looks like.  

So my question is, how much more aggressive does it make it downshift? And why does my transmission downshift when I punch it? Is there anything bad with running without one?

Thank you in advance.

 

[Don C]

The vacuum modulator on the transmission basically sets the shift points. Your kickdown lever, on the transmission, may be tied in the wide-open throttle position, which will give you kickdown, but not operate normally. The C6 won't be damaged by running it without a kickdown (like an AOD will).

 

[will e]

I have been running without the kickdown for years. I use the shifter to kick down. Without the kick down you will notice that at about 65 or 70mph if you step on it, it will not drop into second gear. Mine doesn't but again, I use the floor shifter. I actually prefer the control.

 

[Vinnie]

Edelbrock sells a kickdown extension specifically for using a 1406 on top of a 351C. It's not expensive. I have it (also on a C6) but because I installed a thick spacer the kickdown rod doesn't reach and I've been driving without it.

 

[vozaday]

Good to know, thanks for the response guys. will e you are spot on, it will downshift but once I am up to highway speed it will not kick down to second when I hit it. Was never sure if it was a rpm thing or the lack of the cable. I may track one down just to try it out and see how it feels, not that my car sees the highway much. lol.

I've always been around modern vehicles so before this car I've never owned anything carbureted, or with less than 5 gears. So I'm never quite sure how it should operator normally. Again thanks!

 

[TheRktmn]

I don't mean to steal your thread, but I am wondering:

Does your C6 go from 1st to 3rd as quickly as possible?

Mine does (unless I am driving aggressively) and I was told it was because I have no kick-down.

I have changed and adjusted the vacuum modulator ad even swapped out the valve body for a different one with a different shift kit. No difference.

Has anyone else experienced this?

 

[MeZapU]

Hmm. I never had an original transmission in my car so I can only say the trans does what the valvebody tells it to. If you'd like it to shift with a more performance feel, they try an old fashioned shift kit.

When I bought my car it too was missing the kickdown rod. Never hurt anything. Back in the mid 90's it was tough to find one. Think I got one from a mustang junkyard in Oklahoma. Still needed bushings. After I installed it, it wasn't as big of a deal as I thought. But I guess it was the right thing to do.

 

[will e]

I don't mean to steal your thread, but I am wondering:

Does your C6 go from 1st to 3rd as quickly as possible?

Mine does (unless I am driving aggressively) and I was told it was because I have no kick-down.

I have changed and adjusted the vacuum modulator ad even swapped out the valve body for a different one with a different shift kit. No difference.

Has anyone else experienced this?

Mine does not.  Again no kick down.  I believe the vacuum modulator can be adjusted with an allen screw.  Check this on the web.

I forget how it operates but if there is NO vacuum (line is disconnected) to the vacuum modulator it acts really strange so that is not your issue.

 

[vozaday]

I do find mine likes to be in 3rd by about 25mph. But it will downshift at that low of a speed. I'm very curious. Going to look online for a lockdown and try one out this year. When I bought the car they didn't have the air line hooked up, it was so bad I had to shift it manually around town. You almost had to come to a stop before it would downshift from 3rd. And it would take off from a stop in 2nd.

 

[Bill73Ragtop]

Adjusting the tiny little screw in the vacuum modulator will modify the upshift...to a point. I've often found a new modulator usually needs a bit of adjustment after a transmission rebuild since it often will upshift to 3rd at 25 mph. I prefer a shift to 3rd around 35 mph with nice easy acceleration. Pedal to the metal upshifts are a different animal since the pressure is much higher.

As memory serves, turning the adjusting screw inward raises the shift point.

 

[TheRktmn]

I do find mine likes to be in 3rd by about 25mph. But it will downshift at that low of a speed. I'm very curious. Going to look online for a lockdown and try one out this year.  When I bought the car they didn't have the air line hooked up, it was so bad I had to shift it manually around town. You almost had to come to a stop before it would downshift from 3rd. And it would take off from a stop in 2nd.

Yes! That is what I am seeing.

I had forgotten about the wanting to start in 3rd gear from a rolling stop/slow traffic issue.

 

[TheRktmn]

Adjusting the tiny little screw in the vacuum modulator will modify the upshift...to a point.  I've often found a new modulator usually needs a bit of adjustment after a transmission rebuild since it often will upshift to 3rd at 25 mph.  I prefer a shift to 3rd around 35 mph with nice easy acceleration.  Pedal to the metal upshifts are a different animal since the pressure is much higher.

As memory serves, turning the adjusting screw inward raises the shift point.

I think I need to make sure that the vacuum line is functioning as it's supposed to.

If it is I may try another vacuum modulator and turning the adjustment in.

I seem to recall that there were different ones to choose from and a color stripe told you which you had. Is that correct?

This chart shows which modulator was used in which trans:

http://www.rostratransmission.com/transmission-modulator-application-listing.php

FYI: Broader Performance recommends the black stripe for performance.

 

[Bill73Ragtop]

Link not working for me, but stripes were part of the ID. I have the performance one in my C6 and it does everything you could ask for. Normal acceleration 1st to 2nd is approx 15mph - 20mph, 2nd to 3rd approx 30mph - 35 mph. Pedal to the metal 1st to 2nd is about 35-40mph+ and 2nd to 3rd is approx 50 - 60mph+

 

[TheRktmn]

I could definitely live with those shift points.

I have ordered a black stripe modulator, will let y'all know how it works out.

Also installing a kick-down because....well...I have one now.