904 with very hard 1-2 shift

604B1duster said

I recently got a 66 dart with a 340, 904, and 3.91s. It has a performance build 904. The 1-2 shift is pretty violent. Doesn’t matter if it shifts automatically or if I manually shift it.
I’m wondering if there is something I can do myself to calm it down. I vaguely remember many years ago maybe removing the servo spring in a 727 to get a hard shift ??? Is this a common thing ? It really bangs 2nd gear, no difference 5mph or 40mph. Hoping for an easy fix.
Happy Thanksgiving

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I once mistakenly put a 727 front servo spring into my 904. The 1-2 shifts were bone rattling. It was really difficult to stuff that big spring in there too! I removed the spring after I found out what I did. That resolved the issue. Like junkyardhero said, be sure to check your line pressure to ensure it is not too high. You'll need to pull the valve body to do that, and to access the front servo. Be careful removing the servo cover. If that 727 spring is in there, it will be under a lot of pressure!