Afraid of getting a too technical answer for my question, I'll try here. I already posted this same question on "Gears & Axles" with no success at all.

I'm on the built of an AWD V8 chassis for a project. I'm using a 4L60/65 with T-case removed from a 2003 Silvarado SS.

On the rear we got a 3.15 gear.

What ratio should I use in the front? Same as rear?

I found this old thread with useful info.

LS1 Tech crazyness

Please be nice with thechy language.

 

You have to use the same gear ratio in a front and rear differential in a AWD/4WD vehicle.

This is hardly "Advanced Tech".

 

yes use the same gear in the front. just think about your front wheels trying to turn at a different rate than the back wheels.....it equals fail

 

Fail, and you'd become an overnight celebrity on the internet.

 

...So it really depends on your goals.

 

Are you using the exact same tire and wheel combination front and rear? If you are you need to keep the axle ratios VERY close. If you are not, you need to figure/measure things like revs per mile of the diferent tire/wheel combinations.

As I recall, the Silverado SS T-case is a New Venture 149 which has a viscous coupling and a 38% front/ 62% rear nominal torque split so it won't act like a "solid" transfer case with minor variation in front/rear wheel speed. You still want to match front and rear gears with tire revs/mile as closely as possible. What are your available choices for front gears?

If you had 3.08 fronts and 3.15 rears you might run 245/45-17 fronts and 275/40-17 rears wihich would get you within 1% of same revs/mile. That should work.


Jon

 

I have a friend that bought an old 70's chevy 4x4 for a few hundred bucks. We locked the hubs in the snow on a day of fun on the trails and holy crap... It was fishtailing EVERYWHERE!!! Turns out, it came with 3.73s, but someone had swapped out an entire exle with 3.08's in the rear. When we had it in 4wd the back was spinning a whole lot faster, lol. Good thing we never found any pavement!

 

Thanks guys! I really appreciate all the wisdom shared.
And sorry for the not high tech question, but it seems it is high tech for the "Gears & Axles", and of corse for me.

My question was based on the T-case torque change it does, so I thought maybe the gears were different due to that.

Tires I am using on this thing are: 285/35/19 and 235/40/18 ('06 Vette wheels, not Z06)

 

How much does an Internet star makes? I can get this done with different gears in secs lol

 

I have an awd experiment of my own, http://www.turbols6.com/gallery/view...HOON-LSX-TURBO That 4l60 will not like all that traction.
there is a lot of awd info here, http://www.syty.net/ Look at the drivetrain tech area.

 

But that gearbox was already on a AWD car (Silverado SS) The trany and engine I am using were removed from that car. They are fully stock. (???)

 

AWSOME AWD project by the way!!!

 

This thread is fine where it's at. He tried the correct place first. Looks like he's getting some info in here, so it's all good.

 

Wait wait, do not lock it yet please. I just want to know why the 4L60 I have is not going to like all that traction.

Thanks.

 

http://www.syty.net/ Almost all the high powered sytys even with the the 4.3 are running 4l80e trans, after destroying thier 4l60. when you have excellent traction and a lot of power, it tends to find the weak link, which seems to be the transmission.

 

I dont think he is planning on locking it....

 

That's a lot of difference in tire diameter and revs/mile. 5.7%

You are not doing nice things to the viscous transfer case with that big of a spread in tire size. I would not recommend that combinatiion.

Good luck.


Jon

 

Oh! I got you. Compared to the 4L80 and adding turbos. You were right years ago. Thanks.

When I destroy the 4L60, i might upgrade to 6L**. I like 6 gears.

 

Jon, so if I want to stick with the 2 different diameters, I will need to calculate how much more the font wheels will spin and get a higher gear in the front right?

That means if the difference is 5.7% and I already got a 3.15 gear in the rear I will need 3.329 in the front for almost 0% difference. Right? Smaller wheels spin more right?

By the way, this experiment is making AWD a not AWD car. So I'm starting the chassis from scratch. And I would like to use a GM front differential.

 

Smaller wheels do spin more. In order to spin the wheels faster at the same engine RPM, you need a lower numerical gear, not higher.

285/35/19 = [(285 * .35) / 25.4] * 2 + 19 = 26.85
235/40/18 = [(235 * .40) / 25.4] * 2 + 18 = 25.40

26.86 ~ Tire revolutions at 60mph: 751.02
25.40 ~ Tire revolutions at 60mph: 793.97

Engine Rev's at 60mph 751.02 * 3.15 = 2365
Gear Required for 2365 engine rpm with 793 tire revs = 2.98

Doing the math, you might be better off with a 235/45-18 front tire and a 3.08 gear.