Sorry to Hijack but while we are on the subject of C6's I have noticed mine getting a little soft on shifts the last couple of times I have driven it. I had turned the modulator down slightly as it was very violent (would bark the tyres when not wanted) so thought I might have gone too far. I went in and turned it back up (in) but the adjuster screw was wet with fluid and 1/4 of a turn made no difference when it would usually be significant. So I think it might be rooted.
It is of course adjustable, screw in, silver zinc with what looks like the remnants of a white stripe. My questions are, how many types are there, what is the difference and is one replacement brand better than another? I want to put on exactly the same type as it has now as it is very well suited. Thanks.
First, if you have trans fluid in the vacuum tube, or coming out of the adjuster port, your modulator diaphragm has ruptured to some extent.
Eventually this will get to the point of the vacuum hose filling with fluid and being sucked into the intake....at which point your heart drops due to the HUGE cloud of white smoke billowing from the exhaust.
This is sort of a good/bad thing because at first you will think your engine is done......Then you find the modulator leaking and your day is all better because now you only need to unscrew a modulator to fix things.
There were a few different modulators back when these were the normal transmissions in use.
Today there are basically two (2) "stock" styles to use and there are a few performance versions you can source from trasnmission parts suppliers.
But your auto parts store, or Summit, or other places, can get you what you need.....just be certain you get the proper style (push in, or screw in)
They are spendy now too, often costing between $75-$100.
You will find the two available stock styles with a green stripe, or a white stripe.
The greens stripe is considered the "standard" modulator.
The white stripe is considered the "performance" modulator.
These work within a certain range of vacuum to best suit the engine vacuum profile.
Both will work, but you may not get high enough rpm before a shift with the green stripe....although it still goes pretty high itself when adjusted in all the way.
Some of the older modulators, with adjustment, could be turned enough to "unscrew" the adjuster.....what happens is the adjuster screw threads unseat instead of being retained by the adjuster screw.
All the way out and the adjuster can fall out, but not usually.
All the way in and the adjuster loses its place on the nut and tends to have a variance at times.
Both can be reinserted and adjustment restablished, but you have to be careful because finding the right spot for thread engagement is sometimes touchy....other times it just screws back in with no issue.
As always, be certain you still have the rod inserted into the modulator before screwing the modulator back into the transmission.
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