Still! c4 shifting problems - need to fix it in 36hrs!

[C0V3R]

So far I have been having no luck working out why my c4 wont shift at wide open throttle. It revs all the way out to 6700 rpm and still will not shift! I have tried playing with the kickdown, and fiddling (rotating 2 times ccw) with the vacuum modulator with very little in the way of results.

The vac modulator does not appear to be leaking fluid - can it still be malfunctioning? It was replaced less than 1500mi ago and seemed to be good for about 1000mi.

I was under the impression that even if the modulator isnt working the governor should kick in at some point (5-6k) and force a shift. I dont think I can go any higher than 6700 to see if its going to shift without endangering my engine.

I am scheduled to goto a track day in 36 hours so any help is much appreciated!!

 

[302 coupe]

the governor might be stuck.

You can always just shift it manually, it should shift as soon as you select the next gear.

 

[C0V3R]

Is there any way you can un stick it without pulling apart the transmission?

 

[302 coupe]

you could try some of those magical additives, it would be a longshot though. Best bet would be to remove the driveshaft and extension housing from the trans. The governor is pretty easy to get to. Remove, inspect, clean, reinstall, and keep your fingers crossed.

You can shift it manually, right???

 

[C0V3R]

Not sure if I can manually shift it at WOT. Do you think it would work?

 

[iskwezm]

The vac modulator is on the pass. side of the trans. Make sure the line isnt kinked or the rubber line isnt rotted or sucking fluid. Its a cheap part and quick replacement if it used to work.

 

[C0V3R]

The VM is not sucking fluid and has new rubber line to it. I hooked up a vac gauge and it is definitely getting vacuum.

 

[302 coupe]

Not sure if I can manually shift it at WOT. Do you think it would work?

Everybody that drag races with a C4 always shifts manually at WOT. It never crossed your mind to try????

 

[C0V3R]

I've replaced the modulator, changed the fluid, added additives, changed the lines all with no success.

I tried doing a neutral/drive drop to unstick the governor and at 3000rpm it would not drop into drive. :roll:

 

[C0V3R]

Everybody that drag races with a C4 always shifts manually at WOT. It never crossed your mind to try????

No because I wanted it to shift lower not higher and I assumed whatever was wrong with it would affect that shifting too.

If I shift manually into D (when in 2nd) it happily stays in second until you let off the throttle. Same deal with 1-2

 

[302 coupe]

it should shift when you tell it to, regardless of throttle position. Every C4 I've ever had (been a bunch too) always shifted within half a second of me selecting the next gear, no matter the throttle position or rpm. There might be something wrong with your valve body.