Pros/Cons Going to 3.73 w/T56
08-21-2017, 03:36 PM
#1
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Join Date: Jul 2017
Location: Atlanta
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Pros/Cons Going to 3.73 w/T56
Hey, guys....I plan on sticking with my 274/40 17's, and T56 manual, pulling 420RWHP @6.1 and about 400RWT @4.8 - what can I expect going from stock 3.42's to 3.73's? For Street & Track Days (road racing). Appreciate your direction - thanks, guys.
08-21-2017, 05:23 PM
#2
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,646
Re: Pros/Cons Going to 3.73 w/T56
Can't help with road racing, only street and strip.
3.73's will make it feel like you added about 9% more rear wheel torque, off the line. And you'll be hitting redline at 9% lower MPH in each gear. I went with 3.73's when my Formula still had it's original 6-speed trans. Similar 426 rwHP (without the nitrous), and similar 275/40-17 GS-C's. Enjoyable on the street, with a bit more of a traction challenge on street tire's. 26x11.5-15 Hoosier QT Pro DOT's for the track. No impact on MPG, since it made 6th gear more useable.
In retrospect, I wished I had gone with 4.10's (20% increase) with the 6-speed Where you get into trouble with 4.10's is the possible need to use 5th gear in the 1/4-mile.
3.73 - 26" tire - 6,000 RPM = 124 MPH in 4th gear
4.10 - 26" tire - 6,000 RPM = 113 MPH in 4th gear. You could go with 28" tires, but that puts you right back where you would have been with 3.73's and 26" tires. Or you run it higher RPM on the redline. I was running 11.5 @ 117 MPH on straight motor and the 3.73/26" tire combo.
3.73's will make it feel like you added about 9% more rear wheel torque, off the line. And you'll be hitting redline at 9% lower MPH in each gear. I went with 3.73's when my Formula still had it's original 6-speed trans. Similar 426 rwHP (without the nitrous), and similar 275/40-17 GS-C's. Enjoyable on the street, with a bit more of a traction challenge on street tire's. 26x11.5-15 Hoosier QT Pro DOT's for the track. No impact on MPG, since it made 6th gear more useable.
In retrospect, I wished I had gone with 4.10's (20% increase) with the 6-speed Where you get into trouble with 4.10's is the possible need to use 5th gear in the 1/4-mile.
3.73 - 26" tire - 6,000 RPM = 124 MPH in 4th gear
4.10 - 26" tire - 6,000 RPM = 113 MPH in 4th gear. You could go with 28" tires, but that puts you right back where you would have been with 3.73's and 26" tires. Or you run it higher RPM on the redline. I was running 11.5 @ 117 MPH on straight motor and the 3.73/26" tire combo.
08-22-2017, 07:06 PM
#4
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Join Date: Oct 2004
Location: las vegas
Posts: 1,130
Re: Pros/Cons Going to 3.73 w/T56
3.73 is a good all around gear with a T56. I prefer 4.10s but not in a stock 10 bolt, I shredded my 4.10s 2x in one year
I did a TON of racing though 
After that many years ago I converted to an 8.8 w/4.10s and Moser axles NEVER broke!!!!!
Now I have a different car and it's an A4, I have an 8.8 with 3.73s and an 8.8 with 4.10s waiting....part of me wants to convert this car to a 6 speed
I did a TON of racing though After that many years ago I converted to an 8.8 w/4.10s and Moser axles NEVER broke!!!!!
Now I have a different car and it's an A4, I have an 8.8 with 3.73s and an 8.8 with 4.10s waiting....part of me wants to convert this car to a 6 speed