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Never revved my 400 higher than 3000 rpm. Now, after a rebuild with higher CR I tried the bew power with some WOT sprints but the C6 shifts already at 3500 rpm from 1/2 and 2/3.
I turned in the small screw inside the modulator and and the shift point went up to 4000 rpm. But, of course, now the shift point at cruise speed turned to a higher level, too. When I turn the screw to reach 4500-5000 rpm the cruise shift point is very uncomfortable.
What can I do to have both the benefits ? What can a shift kit help me ?
I´m not familar with transmission, what are your experiences ?
Adjusting the modulator will affect shifts across the board, so now with the changes to your engine - vacuum, compression etc - you may need a different modulator (not just adjusting) to give the right result.
I only know a little about C6s, so that may be dangerous....
I have tweaked governors once or twice. It's much more of an art than a science. There are weights and springs that affect the shift speeds. With the proper tuning (and I never was an expert, and now WAY out of practice) you can move out the high RPM shifts with a small change in low RPM shifts. It's not easy, and it takes a lot of trial and error.
Governor for full throttle shifts and modulator for cruise shifts, that seems the way to go.
That sure would make it easy, if only it worked that way. It doesn't.
The governor produces a pressure. The modulator produces a different pressure. When the governor pressure overcomes the sum of the modulator pressure plus the shift valve spring pressure the trans will shift. You need to modify BOTH pressure to get it to shift when you want. There is a lot of trial and error needed to make this happen.
Mark, you`re not a [I]former[I] transmission engineer .... thank you for sharing your knowledge.
Now, Broader sells a modified governor with shims to play with weights.
Guess I´ll order one and start the trial-and-error play ... but I´m not happy with the preview on multiple oil mess while removing the rear housing.
I would like to have a shift point of appr. 5000 rpm at full throttle but want keep early shift at cruise mode.
Both the modified governor and adjusting the modulator seems the way to go.
With a lightened governor shift points will always be higher, no matter how hard or gently you are stomping on the go pedal.
Governor pressure is controlled by centrifugal force, the lighter an object is the more centrifugal force is needed to move that weight.
More centrifugal force means more RPM's which means higher ground speed.
A heavier weight will move much quicker than a lighter one.
With a modified governor, weights are reduced allowing for higher shift points.
It will not matter how far out the modulator screw is adjusted because engine vacuum won't mean diddly squat at full throttle, because there isn't any.
Some 1/2 tons have a very heavy governor weight that allowed a 1-2-3 shift before an intersection was crossed.
Why not look at a good Transgo shift kit? Stay away from anything with a B&M logo.
Last edited by stuart1; Nov 15, 2011 at 09:50 AM.
Reason: added info
thank you for delivering insight into this. Generally I´m aware of the centrifugal function but you gave me a good explanation.
It´s quite plain to me I can´t have both of it in perfection. My hope is (was ?) the lightened governor provides a considerable higher shift point at full throttle and keeps me in the comfort zone at cruise.
Some 1/2 tons have a very heavy governor weight that allowed a 1-2-3 shift before an intersection was crossed.
Well, the 400+C6 was already in the truck when I bought it 20 years ago. I don´t know where this combo came from.
Why not look at a good Transgo shift kit? Stay away from anything with a B&M logo.
I put this for question in my first post because I do not exactly know what benefit a shift kit will bring me. Do I have to change the shifter as well ?Maybe you can explain the effect of a shift kit to me, please ?
Beside that I would like to avoid removing the trans because due to the tight fit of engine and trans inside the frame and body I must remove engine AND trans. There is a frame crossmember under the trans oil pan what makes it hardly possible to remove just the pan .....