3.90 vs 4.10
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
Advanced
Joined: Apr 2007
Posts: 69
Likes: 2
Another option if you have a 4-speed is to convert it to wide-ratio (If your car is a factory 3.08 it may already be a wide-ratio) and swap in 3.55 gears into the differential. This combination is equivalent to/virtually indistinguishable from a close-ratio transmission with a 4.11 rear end, for gears 1 through 3. 4th gear would then give you the cruise RPM benefit of the 3.55 rear end. Again, if you have a 4-speed and don't mind the greater spacing between gears 3 and 4.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
If you have a bigger tire in the rear, that will change your gearing ratio (i.e., would make a 3.70 gear from the factory drive like a 3.55 ). Keep that in mind.
I run 3.90's with a 27" tire coupled with a wide ratio Muncie in a 69 Camaro, and I love it. Great for horsing around town which is what the car was built for. At 60 she's turning about 3100 RPM (not terrible), but again, it's rare this car is on the highway for longer than 20 minutes.
If I were spending a third or half my time on the highway with a wide ratio Muncie, I'd go with 3.36's, and with a 27" tire, you'd turn about 2650 RPM at 60.
Of course, your cam comes into play here.
Lastly, my opinion, but with the long flat torque curves of the engines we build today, I don' see the need for close ratio Muncies. I'd take a wide ratio with 3.55's or 3.70's over a close ratio and 4.10's. First gear multiplication is about the same, but 4th would be more tolerable with the higher rear gears (lower numerically).
I run 3.90's with a 27" tire coupled with a wide ratio Muncie in a 69 Camaro, and I love it. Great for horsing around town which is what the car was built for. At 60 she's turning about 3100 RPM (not terrible), but again, it's rare this car is on the highway for longer than 20 minutes.
If I were spending a third or half my time on the highway with a wide ratio Muncie, I'd go with 3.36's, and with a 27" tire, you'd turn about 2650 RPM at 60.
Of course, your cam comes into play here.
Lastly, my opinion, but with the long flat torque curves of the engines we build today, I don' see the need for close ratio Muncies. I'd take a wide ratio with 3.55's or 3.70's over a close ratio and 4.10's. First gear multiplication is about the same, but 4th would be more tolerable with the higher rear gears (lower numerically).
Last edited by 73, Dark Blue 454; Oct 14, 2007 at 12:01 AM.
