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Bill, I used the exact convertor that you have in my Cougar with 3.25 gears.

April 20 2017 at 4:04 PM
paulie  (Login Paul_Lovett)

Response to If you are setting up a 9" chunk to put in your car for long trips

I had 255/60R15's at the time which were just over 27" tall.

I think I remember turning rpm's in the 2950 rpm range at 70 mph. This makes perfect sense if you factor in about 5% slip at cruise.

It worked great.

My opinion is that if you want to do highway driving do not go numerically higher than 3.25. Of course, your tire diameter will affect this, but if you're in the "normal passenger car" tire size range this makes sense.

I do not like the "compromise" gear ratios. I call ratios in the 3.50-3.75 range compromise ratios. With them I not happy with either the highway cruise rpm or the with the off the line acceleration. I say choose one or the other and be happy at some point.

Sooooo...... in your case since you are talking about using two different ratios, I think you should get a true highway gear. You already have the 4.33's which do a great job at the other end of the spectrum.

3.25's or 3.00's would be great, in my opinion. The fact that you have a slightly higher than stock stall speed makes me lean toward the 3.25's. I think 3.00's would be okay, too. I don't think I'd go any lower numerically given the torque converter. So where's that put you?

3.00, 3.07, 3.15, 3.18, or 3.25? There's probably other Ford 9 Inch ratios within that range, but the only factory ratios I know of are the 3.00 and the 3.25.

Long story short is 3.25's will work great with 27" tall tires and your converter. Adjust a little bit if your tire size is significantly different than mine were.



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