Super Six setup makes transmission shift too early.

[iprangenberg]

Help with “super six” set up. I just put a 225 super six in my 1971 Plymouth Scamp. I have all the correct parts, although I still have to change the accelerator cable.

The 904 transmission is shifting much too early.I’ve moved the shift rod all the way forward on the bottom transmission swivel, and it shifts too early. I moved the shift rod halfway back on the transmission swivel and it still shifts too early. I’ve tried six different settings and the shift from second gear to third gear is instant.

The transmission shifts great when I shift manually on the column shifter and I know that the transmission is in good condition. any thoughts are greatly appreciated.

 

[volaredon]

Don't think it's the "super 6" causing the problem

 

[Oldmanmopar]

Govenor stuck . Take the tailshaft off and check the spring in the govenor. While your in there change it to a lighter one. It will hold secnd longer then stock when flat out . 340's and max wedge cars were lighter for that reason. 727 and 904 work the same way

Increasing Shift Speeds On The 727 Torqueflite - Mopar Muscle Magazine

If it is a 71 trans could have a bad part throttle valve

 

[RustyRatRod]

You could have a governor issue. But BEFORE you dig into that, here's how you adjust the kickdown properly.

With the gas pedal ON the floor, get under the car and verify that the transmission kickdown lever is all the way BACK in its travel. If it's not, adjust it until it is and then go drive it. If it holds the shift out too far, come back and back off a little until the shift is proper. There are specs for what speed the shift should occur in your factory service manual.

 

[volaredon]

And that shift speed also has to do with how far you're into the gas pedal....

 

[iprangenberg]

Don't think it's the "super 6" causing the problem

Thank you everybody for getting back to me. Last week this car still had a 198 one barrel Holly 1920 and shifted great. I swapped in the 225 with the two barrel and now I’m having these issues. I tend to think that it’s not the transmission because of the excellent drivability I had the week before. I’ve had this car for almost a year.

 

[RustyRatRod]

Thank you everybody for getting back to me. Last week this car still had a 198 one barrel Holly 1920 and shifted great. I swapped in the 225 with the two barrel and now I’m having these issues. I tend to think that it’s not the transmission because of the excellent drivability I had the week before. I’ve had this car for almost a year.

It probably isn't the transmission itself but it IS likely in the kick down adjustment. Here's a hint as to how important that adjustment is.

If you do not get it sorted out quickly, you will burn up that transmission in short order.

 

[Bewy]

The answer is in post $6. You went from a one bbl to a 2bbl carb. Throttle opening will be less with 2 bbl for a given road speed, so shift lever on trans does not move as far & you get an early shift. You will need to mess around with lever ratios. Personally, I prefer early shifts.

 

[SIX225]

Looking at 2nd pic, the linkage doesn't look adjusted correctly. Stud coming off carb looks to be in the middle, but shouldn't it be at the bottom/right of the slotted arm?

 

[iprangenberg]

Ok, I'm pretty sure I have the adjustment wrong. The adjustment nut is at the very end of the kickdown rod, which probably keeps the swivel/arm at the transmission partially engaged at all times, which is why the 904 is shifting instantly. So, that doesn't sound good. So, loosen the nut, open the BBD to WOT, and tighten the nut again. And the kickdown spring needs to be weaker than the throttle spring.

This has to work, will try after work.

 

[RustyRatRod]

Ok, I'm pretty sure I have the adjustment wrong. The adjustment nut is at the very end of the kickdown rod, which probably keeps the swivel/arm at the transmission partially engaged at all times, which is why the 904 is shifting instantly. So, that doesn't sound good. So, loosen the nut, open the BBD to WOT, and tighten the nut again. And the kickdown spring needs to be weaker than the throttle spring.

This has to work, will try after work.

Not what I said and it may not work that way, but good luck with it.

 

[timk225]

I found the best adjustment for the 904 in my '73 Duster to be when the kickdown lever was all the way back just a bit before wide open throttle. Flex in the linkage allows it to still fully open, this is a Holley 350 2 bbl on my 225.

 

[iprangenberg]

Not what I said and it may not work that way, but go

 

[iprangenberg]

I’m really excited to have figured it out and I want to thank everybody for their input. It turns out the rod itself needed to be roughly half an inch longer. Here is a picture of a temporary fix. It pushes the rod half an inch back and now the transmission shifts beautifully. And, yes, the carburetor still opens to WOT.

And as a sidenote, I can’t believe the difference between a 225 with a Carter two barrel compared to a 198 with a Holly 1920. Obviously not like having a V-8, but this slant six is alive. And the Carter makes it idle surprisingly smoothly.

 

[slantsixdan]

The 2bbl (Super Six) setup uses a different kickdown lever – the part attached to the transmission. If you connect the 2bbl kickdown linkage to the 1bbl kickdown lever, you won't be able to get a correct adjustment no matter what.

 

[iprangenberg]

Right! That was my mistake. I didn’t get enough reach. I think 1974 Chrysler switched over to one single universal shift lever on the transmission where the D shape was a different angle compared to the pre-1974 single barrel configuration. Well, there is always a lot to learn.

 

[slantsixdan]

I think 1974 Chrysler switched over to one single universal shift lever on the transmission

First year for the Super Six was '77, and (to repeat myself) I'm pretty sure the 1bbl and 2bbl kickdown lever at the trans are significantly different in length. 2bbl lever shorter, if I recall correctly.

 

[RustyRatRod]

First year for the Super Six was '77, and (to repeat myself) I'm pretty sure the 1bbl and 2bbl kickdown lever at the trans are significantly different in length. 2bbl lever shorter, if I recall correctly.

You're right, they are different, but like you, I cannot recall 100%. Newsflash. That only gets worse. lol

 

[iprangenberg]

One nice aspect about having the "wrong" lever at the transmission and the adjustable nut at the slider by the carburetor pin is that now I can adjust the shift time without jacking up the car and adjusting this at the transmission.

I'm surprised Chrysler made the 1-barrel shift time easily adjustable from the engine bay and required the 2-barrel set-up to be adjusted from underneath the car at the transmission.

The attached image showing my setup is not my image but what I copied in order to make the shorter transmission shift lever achieve the required travel.

 

[slantsixdan]

I cannot recall 100%. Newsflash. That only gets worse. lol

Wait…do I know you?

 

[RustyRatRod]

Wait…do I know you?