Smoother shift with the choke on?

[LaGrasta]

I notice when I first leave the house in the morning when the car is cold, it shifts fantastic with smooth, low rpm shifts. The moment I open the choke, 1st to 2nd is a high rpm shift with a thud. Any ideas?

 

[Asa]

higher rpms make it easier?
does it shift easier when it's warmer?

 

[AZstang66]

It's probably because the choke increase the idle speed from around 600RPM to 1000RPM+. This would reduce the noticeable changes in RPM as the transmission shifts between gears. You could compare it to increasing the RPM while in neutral when shifting between gears on a manual transmission.

 

[LaGrasta]

At first i thought my torque converter was wrong. Then I thought my carb isn't right. Your suggestion of only an idle speed difference sure is simple. I might test that theory this weekend. Thanks for the thoughts.

I'm just looking for a reason to spend way too much money for a new single barrel automizer Pony Carb!

 

[LaGrasta]

higher rpms make it easier?
does it shift easier when it's warmer?

Once it's warm, it still shifts with a thud and feels like it gets hung up until high rpms are reached. I already adjusted the modulator, maybe I should explore that once more.

 

[kirkallen143]

Is your tranny fluid level up to par?
Have you tried adjusting your tranny modulator and/or is there any vacuum leaks in the line to the modulator?
At the nipple there is a bolt inside that adjusts shift rates.

Kirk

 

[CoupeBoy]

up and downshifting are functions of the kickdown and vacuum module adjustments, so don't forget to check that cable..

-ron

 

[Mercury Mike]

Dana's transmissions are funny, he can tell you on the phone how to get rid of that. Did he put the builder's shift kit in that c4 or is it just stock?

 

[grocery getter]

higher rpms make it easier?
does it shift easier when it's warmer?

Once it's warm, it still shifts with a thud and feels like it gets hung up until high rpms are reached. I already adjusted the modulator, maybe I should explore that once more.

LaGrasta, it looks like you have a vacuum or modulator problem. warm it up then back off on the adjustment. if that doesn't work and you are sure you don't have a vacuum problem, look at replacing the modulator.

 

[LaGrasta]

No shift kit is installed
No kickdown cable is installed
Fluid level is perfect, no leaks

After some experiments this weekend, I retract my statement about "warmed-up". Once it warms up, it does shift acceptable, but still not as smooth as when the choke is on when cold. I guess it has to do with the higher RPMs as suggested earlier. The way it shifts when warm is acceptable, but not as I expected. I thought it could be smooth almost to the point you can't feel the shift. 2nd to 3rd is smooth like that, but 1st to 2nd is noticeable. I suspect the engine is so down on power that it has to spin up to get the car rolling and thus hangs up a bit in 1st when doing so.
I'm not saying the car isn't working correctly as much as I'm saying it's not as refined as I thought it could be.

 

[PaulS]

Your choke will increase manifold vacuum when it is on. More vacuum will makethe transmission shift sooner and softer. If you adjusted the modulater did you adjust it clockwise or counter-clockwise? Clockwise will delay the shift points and make them feel firmer. You should never adjust a modulator more than 3 turns in any direction - if you do it could damage the modulator. I also suggest that you mark the modulator with the number of turns and the direction you adjusted it. That way when you feel the need to adjust it again you won't go too far and end up buying a new one.