Vacuum Modulated 4L60E
08-28-2007, 12:09 PM
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Vacuum Modulated 4L60E When going from a smaller cam to a much larger one, what adjustments are necessary if any as far as the modulator? At wot the car shifts firm, but on slow acceleration you can't feel it shift at all and it seems to get into OD really quick. Also, when the converter locks at about 50mph, it unlocks as soon as I get on the gas at all. Is this normal?
08-28-2007, 01:27 PM
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I have a Rossler tranny. The only thing the vacum does is control shift pressure. The electronics still tell the trans when to shift. My trans shifts very smooth and also enters OD quickly just crusing around. You should be able to adjust what (mph) that the trans locks up in. My converter will stay locked when accelerating. I think you can adjust the spring tension on the vacum modulator to make some minor adjustments. Mine doesn't have an external modulator.
08-28-2007, 04:02 PM
#6
well the larger can will cause lower vacumme at idle which will cause a low speed presure increase. However since WOT vaccume would tend to be the same and you dont want to reduce that presure at WOT. I do not see much way you can ajust the higher low RPM line down without affecting the HI RPM presures. So I would imagine you would leave it alone.
Lockup as mentioned and shift timing is still totally a function of the PCM and must be set in the tune as is the lockup kick out under throttle. And of note with a 4000 stall you would not likley feel much in the low RPM shifts
Lockup as mentioned and shift timing is still totally a function of the PCM and must be set in the tune as is the lockup kick out under throttle. And of note with a 4000 stall you would not likley feel much in the low RPM shifts
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08-29-2007, 10:04 AM
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No. It was, but I had it changed back. I'm still not sure whether my converter is unlocking when I give it gas or if 4th gear is starting to slip. If I'm in OD at 70 or so and give it a little gas, it tacks up like the converter is unlocking, but if I do the same in third, it stays locked and no slipping. I'm beginning to think something isn't right in 4th gear. Could that be related to the lower vacuum at cruising speed and the modulator?
08-30-2007, 02:48 AM
#10
If you are having a firm neutral to drive situation, due to low vacuum, you can make it smoother by installing in the forward abuse valve spring a .187" checkball. This will make neutral to drive smoother. This requires removing the valve body to add this.