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C6 downshifts when I let off the throttle

2993 Views 8 Replies 4 Participants Last post by  RJP66F100
Basically the truck downshifts around 1500rpm when I let off the throttle while cruising.
It did this awhile back and got annoying so I switched out to a full manual vb. I hated that as well so I got a Cheetah vb and also switched from a green stripe modulator to a black stripe. Upshifts are nice but the downshifting is back. I tried adjusting the modulator in and out and it doesnt change much. What could be causing this?
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It sounds like how one acts when the kickdown lever is staying applied.
It doesnt have one and the arm was removed and the hole was plugged.
hook a vacuum gage inline with the modulator source . take a reading when backing off throttle
Got good manifold vacuum? Have seen a C4 do similar , guy had hooked modulator to ported vacuum
I switched to a different vacuum port on the carb and it seems much better. Thanks.
Have seen a C4 do similar , guy had hooked modulator to ported vacuum
That's one I've never come across but I can see it happening.
Took a little to figure out .. When the throttle closes vacuum drops to zero so trans thinks its at full load and downshifts ..
One I've come across more than once:

EGR valve hooked direct to manifold vac.

Hmm... I wonder why it runs so rough:):)
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