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New member
Hello my name is Joseph Mangelos and although I’m not a new member I am now the proud owner of a Unique 427SC. It has a 427 Sideoiler, close ratio top loader 4 speed and Jag rear with 3.31 gears. I was hoping some of the more season members could give me a little advice. I drive mostly in town and first gear with the 3.31 gears seems too high. If I change to 3.70 gears then I would be tacking about 3300 Rpm’s at 70mph which I think is a little much for a big block. My thoughts are to go to a TKO 600 5 speed and was wondering what you guys thought about that?
Thank you in advance and if your ever in the Ripon Ca area please call if you need a place to stay for the night or some mechanic work. 209-614-0456 Joe |
I don't know what rear end you have, the 8.8 or 9 inch but I run 3:91s in my 69 NASCAR Cobra as that was the highest I could get when I ordered it and I have ran that engine for all these years and not hurt it. The horsepower peaks at 6,300 RPM so running 3500 to 4000 hasn't hurt it at all. In my Coupe with the 8.8 rear end I run 3:73s and it works well as it has the 8.8 rear end and the Cobra has the 9 inch rear end. You will notice a drop in gas mileage with the lower gears.
And congratulations on the new Cobra. You will have a lot of enjoyment from it. Ron |
I think a TKO 600 .82 fifth gear will be nice with the rear gear you have.
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I think selecting rear end ratios depends on how you drive the car. I'm rebuilding a wrecked car and have done a ton of research in trying to select gears. The PO bought the car with 3.0's and said he felt like he could never get out of second gear while driving around town so he changed them out to 4.11's. Now I'm thinking he went the complete opposite extreme. While the axle was out I put 3.70 gears in. I have yet to drive the car so I cannot make any input on the change.
On another note I was talking to a Cobra owner at a car show and he when the other way. He had either 3.70's or 3.73's and when to a 3.0 for the sake of gas mileage. My car and his both have 5 speed transmissions. |
The problem is that you have a close ratio top loader instead of the wide ratio. the close ratio is made for racing and is too tall for street driving, especially in town. The cheapest fix would be to change the gearing in the transmission to the wide ratio. Race cars like the close ratio as it keeps the rpms closer together between 2-4. On the street you want first gear to have a shorter mph range so that you can get into second gear sooner.
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if you go to a tko600 (with a 2.87 first gear), I'd leave your 3.31 gears alone. If you keep your toploader, i'd might keep the 3.31 gears also, i.e. your first gear is kind of a 2nd gear; I'd rather have that than having a 4rth gear that revs you so high at 60-70 mph.
Given power and weight, I think the optimal first gear final drive, i.e. 1st gear ratio x rear gear ratio, to be in the 8.0-9.0 area - that way you get a nice pull in first, not just 20-25 mph and then have to shift. I like to be able to get up to 50 mph in first at about 5000-5500 rpms. |
Welcome to “The Club!”
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Try using these 5 speed calculators to model what you'd like to achieve.
https://www.5speedtransmissions.com/calculators |
Thanks to everyone for all the thoughtful replies, I have a lot to think about concerning transmissions (change trans gears or go to a TKO600), that said I just love the Cobra.
Thanks again Joe |
Unique makes a nice car. Welcome to the club.
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1 Attachment(s)
This is a great tool from the ERA website - Page 11: http://www.erareplicas.com/freeman/427.pdf
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