Rear axle ratio opinions

[Biggut]

Just a quick question. Need opinions on what rear-end ratio to run in my 67 with a 390 and a C6. It has the 3.70 right now, and it is WAY too low. I don't use it to pull or haul anything; just a street cruiser. Thanks for your input!

[Caseys71]

How tall of a tire are you running in the rear? Depending on the size of the tire I'd say around 3:25-3:50ish, or if you ran a bigger set of tires in the rear that would lower your RPMs as well and give you the same affect as a higher gear.

[Biggut]

Running 23570r15's. Not sure how tall tey are, but I can measure them tomorrow.

[mrtleavitt]

I would say 3.25. You aren't going to see a huge jump from 3.70 to 3.50- I think that gives like a 250 rpm decrease. Since it's way too low like you say, make the bigger jump to 3.25 gears.

[TX69F100]

Where are you located?

I'm looking to swap to a 3.70 and have the 3.25.

[Biggut]

Do you think the 3.0 would be too tall. What usually came stock in a bump with a 390 and a C6? I'd trade you, TX69F100, if it wasn't so far from Idaho to Texas.

[gregamorton]

2.75s or 3.00s I would go with for a driver. 2200 -2500rpm or so at 70. You could go with a set of 2.47s if you drive on the highway everyday. Those would put you around 2000rpm or so.

[69rangerf100]

i have a 69 F100 it has a 390 manual 3 spd and a D60 with a 3.54 gear ratio

[Biggut]

Thanks to all for your help! I'm not nearly so lost now.

[cdeal28078]

I have a 3.25 in my 71 F100 460/c6 and it is OK. I had a 3.0 originally and liked it better. Mostly because of the torque of the 460 though. I would say either the 3.0 or 3.25 and wouldn't go any "higher" than those two.
69ranger F100 do you have 16" tires on the Dana 60 with the 3.54? I wonder how much taller your tires are than a 235/15 if any. I think a 235/15" is around 29 inches tall if I remember right, which I probably don't
clint