63 Impala Rear End Gearing

Peter Birmingham

Well Known Member
My friend has a 63 Impala with a 409 and a four speed transmission, the rear end gear ratio is 4.10:1. It seems when he runs at highway speed, 60 - 70 the car really has a humming to it. He wants to use the car as a cruiser but still have a little snot off the line. Would changing the rear end gear ratio to 3.70:1 or 3.50:1 make it run smoother? How about a 3.20:1 ratio? I really don't understand the ratios, that well, looking for some help.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
Agreed,if his 409 is a 340 horse type 3.36 would be a good choice,a solid lifter 400-425 horse would be better off with 3.55 for cruising around at todays freeway speeds.
 
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