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Recently put in a C4 from TCI - Super Streeter. Running a 347 with 2800 stall and 3.44 gears. In auto mode car shfits into 2nd and 3rd too early. Shifts out of 1st rolling out of the driveway (can't even feel it) and into 3 at about 20 mph. Been playing with modulator, tightening inthe modulator screw. Shifts a little firmer in 3rd now but 2nd still comes on way too early . I can keep playing with modulator tightening it up (turning in) but want to see if I'm chasing the right solution. Also does anyone have any specs on what the shift points should be. I call ed TCI support line - not too impressed with their support. Any advice would be appreciated. thanks
 

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Don't turn the modulator adjuster more than 2-3 turns in either direction. If you already have done that the replace your modulator. while you have the modulator out check the length of the pin between the modulator and the valve. It should be 1 5/8" long or slightly longer. (1.625" +/- .030") You can make a replacement using an 8d nail.
 

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I should tell you that low rpm shifts are good for your C4 under light throttle. It keeps wear to a minimum and is more comfortable than a later shift. Late shifts under light throttle results in "sliding" shifts that make the friction surfaces slip into and out of gear. Under moderate throttle the shifts shold be very quick and firm with no signs of slippage. A performance C4 will shift so quickly that you may not even notice the shift under light throttle but when you floor it the transmission seems to shift harder because although the shift happens at nearly the same speed there is a lot of momentum behind it when at higher rpm.
 

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Discussion Starter #4
Yes I did turn out more than 3 times. Order a new modulator. Also, when I took the modulator out to adjust (could not reach while in) I did not see the that their was a pin - fell in bucket I was using to catch oil. Put i back w/o it. Will reinstall when I put on new modulator. I did drive it w/o the pin for a while - could I have caused any permanent damage? Seemed realy to make no difference except 3rd was a little hard. Should have done some research before I started playing with it. What a newb! Thanks for the advice.
 

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You say "screwed out' ?? That will give early shifts .. Screw in makes the shift later.

Paul what happens if screwing too far in or out , just wondered i haven't done it just curious . I set my modulators on scales as per Transgo .
 

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I set them using a scale and fixture too but I have seen modulators that were ruptured and had broken springs from being turned too far in.
I usually recommend no more than two turns either way for my customers but then they begin with one that is properly set up. I believe TransGo says three as a maximum.
 

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Discussion Starter #8
Sorry I meant screw in.

Made a new pin out of 8d nail and put new modulator in. Back to shifting where it was prior to messing with it. Decided to leave well enough alone. If I want longer shifts I will do manually. thanks for the help.
 

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Just did the same thing with my new C6 and also came to the same conclusion. Only thing I can think that will be hurt by the early shift like 3rd gear at 20mph is a lot of heat produced by 2800 stall with load under the stall speed for an extended time.

Just my $0.02
 

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Sounds like you will need to get involved with the secondary piston & the secondary spring in the governor.
The piston you have is probably too heavy & the spring is too stiff.
You need a lighter secondary spring & maybe also lighten the secondary governor piston.
This is not fun, since you have to remove the tailshaft housing to access the governor.
I sell a lighter spring for $15.00 shipped to the lower 48 states.
You need to measure the weight of the secondary piston in grams & advise. Bill
 

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Sounds like you will need to get involved with the secondary piston & the secondary spring in the governor.
The piston you have is probably too heavy & the spring is too stiff.
You need a lighter secondary spring & maybe also lighten the secondary governor piston.
This is not fun, since you have to remove the tailshaft housing to access the governor.
I sell a lighter spring for $15.00 shipped to the lower 48 states.
You need to measure the weight of the secondary piston in grams & advise. Bill
The governor doesn't have anything to do with part throttle shifts. It controls full thottle shifts only.
You should make sure that your down-shift linkage is correctly adjusted. I think the pin in a C6 is a different length but I would have to check the specs to be sure.
 

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I had one C6 i had to use a longer pin with the new modulator. Seemed the replacement modulator the pin sat in deeper and was loose where in the original had a little preload .

Make sure when the modulator is pushed in there is a little preload in the last bit as you push it in the case . Should feel it springy
 

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The governor doesn't have anything to do with part throttle shifts. It controls full thottle shifts only.
Paul i have worked on several C-4's where the part throttle shifts were normal & just going from a 11 gram secondary piston to a 8 gram piston the part throttle shifts were way too high.
This could be a yes or no situation because the full throttle shifts in drive were perfect with the 8 gram piston, but just a little too low with the 11 gram piston.
I made no adjustments to the modulator so i will not argue that fact.
All i'm stating that the weight of the secondary piston did change the part throttle shift point.
The next governor mod i do i will experiment with the vacuum modulator & see if it makes a great change or just a small change.
Good point & next time i will be able to give better feedback. Bill
 

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I know this is an OLD thread. I'm trying to resurrect it.

I have the same issue with my rebuilt C4. It shifts at 4000 at WOT.
I want it to shift about 5500 at WOT.
I tried turning the mod screw in 3 turns and it didn't help.
It is back where it was now.

If the governor spring is still available, I want one. I also want the lighter piston. The trans is out of the car right now so taking of the tail shaft is no problem.

Thanks
Danford1
 

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Lengthing the mod. pin, WOT shifts raised to around 4000rpm, with lighter spring, Sonnax governer we get to approx. 4500-4800 rpm.
I'm told the answer to max, shift points at WOT, other than shifting manually, is a performance valve body, but, would like to know if this is a viable way to go & any suggestions on suppliers
 

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i have the same problem on my c4
71 f100. rebuilt trans unknown by who or exactly when.
302 perf built. cam. holley. headers. ported heads etc
1to 2 very quick. 5 mph
2 to 3 at 20 mph. itll shift back to 2 for a sec. then up to 3.

ive been told bad valve body. or bad setup in valve body?
ideas?
it shifts so soon. it really wont let engine rev and get in power band.
 
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