Best Gears for C5 A4
Thread Starter
Intermediate
Joined: Jan 2025
Posts: 38
Likes: 1
3.73 or 3.90 Gears for C5 A4?
Hey guys, the time has finally come to upgrade the stock 3.15 gears in my C5.
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
Last edited by jackmatt3; Sep 1, 2025 at 03:04 PM.
Melting Slicks
Joined: Sep 2021
Posts: 2,555
Likes: 1,213
Hey guys, the time has finally come to upgrade the stock 3.15 gears in my C5.
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
What is your goal? Do you care about wheel spin? Future horsepower upgrades planned?
Race Director
Joined: Jan 2000
Posts: 10,376
Likes: 3,386
From: Central TX
C5 of Year Finalist (appearance mods) 2019
Hey guys, the time has finally come to upgrade the stock 3.15 gears in my C5.
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
I'm unsure if I should upgrade to 3.73 or 3.90 gears. Curious to know what others are running.
*The car is currently N/A with a cam and heads setup, I am running 345/30/20 tires in the rear and 275/35/19 in the front.*
A 345/30/20 tire is 28.2" diameter, really tall to fit a C5. Are they 345/25/20's, instead?
Drifting
Joined: Jul 2004
Posts: 1,679
Likes: 692
From: Pingree Grove IL
Honestly, you might like the 3.15 gears with a supercharger. But I definitely wouldn’t do more than a 3.42 gear. Maybe a 3,000 or 3200 stall regardless if you stay with the 3.15 or go 3.42.
im currently running a 3.73 gear, 3200 stall, bolt on NA coupe.
im currently running a 3.73 gear, 3200 stall, bolt on NA coupe.
Thread Starter
Intermediate
Joined: Jan 2025
Posts: 38
Likes: 1
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Thread Starter
Intermediate
Joined: Jan 2025
Posts: 38
Likes: 1
I like the idea of going SC but I’m not against keeping it NA due to the miles on the motor.