Transmission 727

[wilky70]

I recently purchased a 1970 Roadrunner. I wasn't able to test drive it before I bought it because of the snow we had. Now that I have it home I'm finding the transmission shifts very hard on light acceleration and extremely hard under hard acceleration. I have done some research on google but it isn't clear to me. looking at the two pictures one with the spring and one with it off, should I be increasing the length?
Thank you in advance.

 

[Don Frelier]

It likely has a shift kit in it.

 

[dadsbee]

Said spring does nothing but insure that the throttle pressure linkage returns. Has nothing to do with how it shifts. That said "hard" is good...

 

[R413]

Nice A13 road runner.

Shift kit will do this. The throttle pressure linkage should be all the way back at wide open throttle from the pedal inside the car. Get a helper to floor it.

 

[wilky70]

Said spring does nothing but insure that the throttle pressure linkage returns. Has nothing to do with how it shifts. That said "hard" is good...

I thought possibly that it was indicating that the TV linkage should be made longer.

 

[RR Fan Dan]

It likely has a shift kit in it.

Nice A13 road runner.

Shift kit will do this. The throttle pressure linkage should be all the way back at wide open throttle from the pedal inside the car. Get a helper to floor it.

Agree. It’s probably a shift kit. Which is good.

 

[wilky70]

Nice A13 road runner.

Shift kit will do this. The throttle pressure linkage should be all the way back at wide open throttle from the pedal inside the car. Get a helper to floor it.

I will try that tomorrow. Do I have it correct that if I lengthen the linkage the shift is softer and if I shorten it the shift is harder?

 

[GTXDAN]

In that bell crank where the linkage goes down behind the motor there is a rig pin hole. With a pin (drill bit that fits hole) in the hole the lever on the transmission should be forward against the stop and the slot on the arm against the carb pin. Service manual shows it all.

 

[wilky70]

In that bell crank where the linkage goes down behind the motor there is a rig pin hole. With a pin (drill bit that fits hole) in the hole the lever on the transmission should be forward against the stop and the slot on the arm against the carb pin. Service manual shows it all.

Thank you, I ordered a service manual from Rock Auto tonight.

 

[dvw]

It's not really kick down linkage. It is throttle valve linkage. It's designed to increase line pressure with the application of throttle. Shortening it will reduce pressure somewhat at a given throttle opening. It'll also make the shifts occur at lower rpm. Better to take a pressure reading. If it's over 100psi with the linkage full back at idle? You may be able to adjust the line pressure back on the valve body with the allen screw. Or as stated it may have a shift kit with a heavier pressure regulator spring installed. You could swap it with a standard spring. I would not adjust the pressure below 95-100 psi with the linkage fully rearward.
Doug

 

[not so famous bob]

Said spring does nothing but insure that the throttle pressure linkage returns. Has nothing to do with how it shifts. That said "hard" is good...

mine will rattle the u joints and bang like hell at non pulling acceleration , if I shift manually , or let it shift automatically under load it is almost stock feeling , except for how quick it shifts ..
I don't particularly like it ...

 

[Photon440]

Thank you, I ordered a service manual from Rock Auto tonight.

You could also download the online version from here:
Service Manuals – MyMopar

 

[zyzzyx]

Would it be possible to ask the previous owner? If not, drop the pan and look for obvious shift kit parts installed.

 

[wilky70]

It's not really kick down linkage. It is throttle valve linkage. It's designed to increase line pressure with the application of throttle. Shortening it will reduce pressure somewhat at a given throttle opening. It'll also make the shifts occur at lower rpm. Better to take a pressure reading. If it's over 100psi with the linkage full back at idle? You may be able to adjust the line pressure back on the valve body with the allen screw. Or as stated it may have a shift kit with a heavier pressure regulator spring installed. You could swap it with a standard spring. I would not adjust the pressure below 95-100 psi with the linkage fully rearward.
Doug

I'm new to this. Where would I check the line pressure? Is there a test port on the transmission? Is this something I can do myself in my shop? My sense is that this car was restored to OEM specs but never driven and needs a bunch of sorting.

 

[wilky70]

Would it be possible to ask the previous owner? If not, drop the pan and look for obvious shift kit parts installed.

I will try and contact him. I purchased the car from a dealer but I have the owners contact info.

 

[dvw]

I'm new to this. Where would I check the line pressure? Is there a test port on the transmission? Is this something I can do myself in my shop? My sense is that this car was restored to OEM specs but never driven and needs a bunch of sorting.

There are 4 test ports. 3 on the right side of the case, 1 on the tail shaft. The one you want is on the in the middle of the case. Disconnect the throttle pressure linkage. Run the engine at idle and move the throttle pressure lever full rearward. That will give you line pressure The fitting is 1/8" pipe. Any gauge that reads over 150 psi will work.
Doug

 

[wilky70]

There are 4 test ports. 3 on the right side of the case, 1 on the tail shaft. The one you want is on the in the middle of the case. Disconnect the throttle pressure linkage. Run the engine at idle and move the throttle pressure lever full rearward. That will give you line pressure The fitting is 1/8" pipe. Any gauge that reads over 150 psi will work.
Doug

Thank you.

 

[wilky70]

It's not really kick down linkage. It is throttle valve linkage. It's designed to increase line pressure with the application of throttle. Shortening it will reduce pressure somewhat at a given throttle opening. It'll also make the shifts occur at lower rpm. Better to take a pressure reading. If it's over 100psi with the linkage full back at idle? You may be able to adjust the line pressure back on the valve body with the allen screw. Or as stated it may have a shift kit with a heavier pressure regulator spring installed. You could swap it with a standard spring. I would not adjust the pressure below 95-100 psi with the linkage fully rearward.
Doug

Hi Doug, I had some time today to try and adjust the length of the throttle valve linkage. I now see how it affects the shifts. I was able to make it so the shifts are firm but don't hammer the way they did. The 2-3 shift is perfect, the 1-2 a little hard but acceptable. I ordered the transmission pressure gauge kit from Summit and will confirm the pressure is correct. I'm also going to change the filter and fluid as I know fluid type can affect the shifts.
Thank you for your great advise.

 

[Rebelrouser]

I recently purchased a 1970 Roadrunner. I wasn't able to test drive it before I bought it because of the snow we had. Now that I have it home I'm finding the transmission shifts very hard on light acceleration and extremely hard under hard acceleration. I have done some research on google but it isn't clear to me. looking at the two pictures one with the spring and one with it off, should I be increasing the length?
Thank you in advance.

View attachment 1833461

View attachment 1833462

As mentioned probably has a shift kit in it. And if you can drop the valve body they most likely left the spring out of the accumulator. Putting that spring back in will calm down the harsh shifts in my experience.

 

[wilky70]

As mentioned probably has a shift kit in it. And if you can drop the valve body they most likely left the spring out of the accumulator. Putting that spring back in will calm down the harsh shifts in my experience.

I'm going pull the pan of this weekend. I've never worked on a 727 before but I will google the location of the accumulator.