Thinking about going to 4.10 gears since i need new ones anyways.

But i hear alot of people say dont higher then 3.73's in an A/4.
Why is that?

Is it because they are weaker?

 

i may be incorrect on this, but i've heard that its because you could shift into OD with a 4.10 in the 1/4 mi depending on your shift points and that is hard on the tranny....for instance if your in 3rd at 5700 rpm with a 4.10 and 26" tire your going about 107 mph....if thats your shift point and your trapping 110 in the 1/4 it would shift into OD at WOT and OD is not made for that kind of load

 

4.10s are perfect for a stock cam car or for a car with a long duration cam.

 

Well, if I had an A4, I wouldn't want to be turning 2100-2500 rpm on the freeway all the time.

Dan

 

i love mine on the street, the only bad part is highway racing my car wont shift into overdrive at wot.

 

i will be shifting at around 6000-6200 rpms with a cc306 cam and 16in wheels. I am guessing i will be around 12.5 in the Qtr.
I dont know what that translates to in the 1/4 mile as far what gear i would be in.

As it is now if i am on the Hwy i crusie at around 2500+ rpms.
I dont hit the hwy that much right now.
The car is currently a DD but it will be a weekend driver soon.

The only reaso i want to change is because i could really tell the diference going from 2.XX gears to the current 3.73's and i think the car would feel even better with 4.10's

 

the only way it is a good idea on a modded car to run 4.10's is with a 28" tire.

3.73's or 3.90s is about max that most people use in automatic cars

 

4L60E, 4.10 gears, 26" tire, 3rd (1:1) gear will net you 114 MPH @ 6,050rpm. You can run a 12.5 at about 108 MPH, but allowing for traction issues, etc, it's possible you would have to be trapping a bit higher than that to run 12.5's. Your solutions would be to go to a 27" tire. Or rev it to 6,200 for 117 MPH.

 

I have 4.10 gears in mine but I'm running the local 1/8th with a 28" tire too. They are good gears but I had zero traction on the street.

 

Street traction is not a problem for me, i run M/T drag Radial on the car all the time.


What is a 27" tire? I know the 255/45/16 stuff but how do i turn that into **" tire?

 

I went from 2.73s to 4.10s its crazy but the only thing that sucks is I get about 200 miles per fill up and 3000rpms on the interstate at 70. Now I'm going with the cc306 so I'm going to have to buy a differnt dd.

 

Why not go with a cutom cam instead?
I have the cc306 cam, i like it but you can get the same gains with a custom cam and not have to spin the motor up so high.

 

The 27" is the diameter of the tire in inches.

 

If you stayed with the same rim, you would have to increase the second number by the correct proportion of you tires tread width which would equal .5 inches, that will increase your tires diameter by 1".

Ex. I have 275/35/17.
275 = cross sectional width (millimeters)
35 = the ratio of sidewall height to cross sectional width (percentage)
17 = wheel diameter (inches)

Current side wall height = .35 * 275 = 96.25mm (/ 25.4 ~ 3.79")
Current wheel height = 3.79 * 2 + 17 ~24.58" (lets call it 25")

Increase by 1" (25 to 26)
have to increase sidewall hieght by .5" (* 25.4 = 12.7mm)
12.7 + 96.25 = 108.95
108.95 / 275 = .396 (close to .40)

IF my calculations and assumptions are correct. I would have to run 275/40/17 tires to roughly increase tire diameter by an inch.

 

Thanks for the break down, i never understood how to gett to that number before.