Shift problems

bigbear89406 said:

I have sum FR500 chrome rims that are 18" when i put these on my 94 they make my trans shift funny but when i put the 16's back on it clears up has anyone had this problem or know whats going on??

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What do you mean by shifts funny? What are the tire sizes for the 16" and 18" rims? If you mean that the shift points have slightly changed that would indicate that the overall wheel and tire diameter are different between the 16" and 18" wheels. You would also see an error in the speedometer reading.

Is it behaving the same whether it's downshifting 2nd down to 1st and 3rd down to 2nd gear? Have you changed the speedometer driven gear for the 3:55 gear change? Is there a shift kit that's been installed? The tire overall diameters appear to be the same so it can't be anything directly related to the different sized wheels. I suspect the issue probably occurs closer to the 5000 rpm range (not 4k) and it may be that you are hitting the rev limit (about 5.2k-5.4k for an AODE) before the shift point. IIRC the Ford PCM shift point is based on throttle position vs. speed. If the speed calculation is incorrect I can see where the rev limit may be reached before the expected shift point causing what you describe as hanging. If what I'm saying is correct I'm still puzzled that the change in wheel size seems to be part of the equation when the tire height is the same.