I was wondering if anyone can tell me if the screw inside the vacum port of the shift modulator on a C6 adjusts the 2-3 shift or the 1-2 shift. I was told that this adjusts the shift points but not which one. I would like to set mine up to shift out of first a bit later. It shifts out of first at about 1000 RPM or 5-10 MPH right now and shifts into high at about 2100 RPM. The 1-2 shift is soft but the 2-3 shift lets you know it's there. I am hoping that this will help to firm up the 1-2 shift as well. If anyone has adusted theirs or has a C6 behind a diesel please let me know what your shift speeds are and if you have adjusted them successfully. Oh Yeah. I am running a 4.10 rearend.Thanks in advance!

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Hey Brad

The modulator only tells the trans where your pedal is, kinda like a detent cable on newer trans, try adjusting the vacuum control at the injector pump. Move the adjustment forward, or counter clockwize. This will delay the sift. Before though, make sure there is no oil in the vacuum line, as you may have a bad modulator.

Let me know how it goes,

Dave

http://a2ztowing.homestead.com/a2ztowing.html

 

Hey Dave,
I replaced the modulator about a month ago. I adjusted the Vacuum control like you said. It worked good. It is now coming out of first at about 1700 RPM and hitting second at about 25-- RPM. A little goes along way when adjusting this thing I moved it about a quarter inch to start and it held 1st until 2500. LOL. Thanks again.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Good deal, Yeh I forgot to tell you move only so slightly. It has been my experience with these motors to adjust the vacuum valve instead of the modulator, as the modulator is set at the factory, and should be ok.

Dave

http://a2ztowing.homestead.com/a2ztowing.html

 

While we are on the topic. Which modulator is which? I had one with a green stripe in it and I put one with a black stripe into it. I got it from the Ford House down here and they tend to be rather clueless to any vehicle over 5 years old.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

While we are on the topic. Which modulator is which? I had one with a green stripe in it and I put one with a black stripe into it. I got it from the Ford House down here and they tend to be rather clueless to any vehicle over 5 years old.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6