Camarothatcould

iTrader: (3)

First thirdgen Ive had with such a turd gear. Want to swap in a 3.73. car will remain stock TPI and auto.. Am I going to run into any issues? What RPM can I expect @ 65MPH?

Ron U.S.M.C.

Two things I can think of that may effect that gear choice is one, the700r4s short first gear. I went from 2.73 to 3.42s and off the line 1st pulls good and hard for a nice stretch and then shifts with enough force/torque to bark the tires nice and loud. Posi grabs and another nice stretch and the tires chirp from 2nd to third. I don't like the idea of going through the gears any faster than that. 3.73s and you will lose more of 1st than you may want.

Second if this car sees the 1/4 mile you stand a chance of running out of gear before you pass the line. You want a gear that tops out just past the line not before it. 3.42s in OD at 65 or 70 is tolerable using the ear tech. The other does not work.

I know I don't give specific times/mile per hour at shift points or exact tach readings but this gives you a few points to take into consideration. Maybe someone else will chime in and fill in the blanks.

Here’s how I changed my ratio.

https://www.thirdgen.org/forums/tran...de-photos.html

Camarothatcould

iTrader: (3)

Awesome write up. Thanks.

Thing is this will most likely be the only modification I do to the car with this current engine/trans combo so I kinda want to milk it for what it's worth.

My last iroc had a 3.73, but a way bigger power house and it would break em loose way into 3rd.

sofakingdom

iTrader: (1)

That's too much gear for that motor. You'll take it from one aspect of turd, to the opposite one. (hmmm... from steaming, to runny, maybe? iunno....) What you'll end up with, is one of those things that feels like a rocket launcher off the line, but you won't be able to shift it fast enough and it will sort of "hover" at the shift points because it's so played out it can't build up even one more RPM; and you won't be able to pass a semi at 55 on a 2-lane road because you'll storm right up to about its 5th wheel and then won't be able to get any farther.

3.42 was borderline too much in the G92 cars. That's ABSOLUTELY as far as you should go if the motor is to remain stock.

At 65 mph, you'll be out of the motor's power band. No "calculator" will tell you that, so they're USELESS for understanding the situation at hand.

jmd

iTrader: (4)

If keeping the long tube runner intake, go 3.42.

Ron U.S.M.C.

I spent a lot of time planning my 10 bolt build because of the length of time it took me to save the money to get it done. I talked to the installer and owner of the shop that was doing the install. The shop is called "The Rear End Shop" and all they have done for the last 20 years is differential work.

He’s one of the main reasons I picked the 3.42s. That and doing a ton of reading on this site. The engine in my car is stock other than an open air intake element but the new gears make it feel like I added 40 hp.

One thing I can sajest to make your shifts nice and firm is by passing the shift kit for now and just install a Corvette servo for about $25.00 and you can do it your self. It has allowed me to skip a shift kit because of the way the servo is performing.I talked about barking the tires when the car shifts gears and along with the gear change the fast,ferm shifts are what make that possible.You can feel when the car shifts gears including down shifting because of the Trans grabing. Heres a link I used to get the job done. You’re going to love it.
http://sethirdgen.org/servo.htm

Camarothatcould

iTrader: (3)

I've had a brand new vette servo in my box for years. Forgot about it til now. lol