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My 72 Mach 1 Q Code has a C-6 tranny. The problem is that when it's in Drive and I'm starting from a stop, it will shift into 2nd then 3rd before I reach 10 mph. I had it in the shop and they said that it was the modulator valve so I had them replace it but no improvement.

I'm running 3.70 gears and am wondering if that can have anything to do with it. Doesn't the tranny rely on engine vacuum to decide when to shift? Could it be that because I'm at higher RPMs quicker then it would shift quicker? It works fine otherwise.

I shift it manually now because of this. It's no big deal, but there are times I just want to put it in drive and go.


My 72 Mach 1 Q Code
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