3.08 to 3.42 axle swap - CamaroZ28.Com Message Board

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3.08 to 3.42 axle swap

Old 07-07-2017, 02:00 PM
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3.08 to 3.42 axle swap

I've found a 3.42 posi from an 02 Formula Firebird that I want to swap into my 96 Camaro V-6 replacing the 3.08 that's in there now. Car is an automatic.

Any idea how much this will throw off my speedometer and do I need to have anything done to the transmission?
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Old 07-07-2017, 09:20 PM
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Re: 3.08 to 3.42 axle swap

Speedo will read 11% higher than actual speed. Example

At true 50 MPH speedo will read 55.5 MPH, at true 80 MPH speedo will read 88.8 MPH.

Odometer will add 1,110 miles for every actual 1,000 miles you drive.

Transmission shift table will be thrown off, since the PCM shifts the 4L60E transmission based on trans output shaft speed and throttle position percent. The 3.42 gears increase the trans output shaft RPM by 11% as well.

New gear ratio needs to be programmed into the PCM to correct all of the above.

The rear brakes are different on a 2002 compared to the 1996, particularly the e-brake linkage. You would have to swap your 96 rear brakes to the 2002 axle, or adapt your e-brake cable to match the 2002 brakes. I know that's true for the rear wheel disc brakes (standard on V8 cars, optional on early year V6 cars), not sure how that would work if your car has drum rear brakes.

Then there's the issue of ABS and ASR (traction control). An ABS only rear will have a single wheel speed sensor on top of the differential housing. An ABS + ASR rear will have a rear wheel speed sensor on the end of each axle/backing plate.
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Old 07-08-2017, 07:37 AM
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Re: 3.08 to 3.42 axle swap

Fred figured out what the discrepancy by dividing: 3.42/3.08 = 1.11, or 11% higher.

That assumes you have the stock tire size and that you wouldn't change to a different tire size at the same time.
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Old 07-10-2017, 11:25 AM
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Thumbs up Re: 3.08 to 3.42 axle swap

Originally Posted by Injuneer View Post
Speedo will read 11% higher than actual speed. Example

At true 50 MPH speedo will read 55.5 MPH, at true 80 MPH speedo will read 88.8 MPH.

Odometer will add 1,110 miles for every actual 1,000 miles you drive.

Transmission shift table will be thrown off, since the PCM shifts the 4L60E transmission based on trans output shaft speed and throttle position percent. The 3.42 gears increase the trans output shaft RPM by 11% as well.

New gear ratio needs to be programmed into the PCM to correct all of the above.

The rear brakes are different on a 2002 compared to the 1996, particularly the e-brake linkage. You would have to swap your 96 rear brakes to the 2002 axle, or adapt your e-brake cable to match the 2002 brakes. I know that's true for the rear wheel disc brakes (standard on V8 cars, optional on early year V6 cars), not sure how that would work if your car has drum rear brakes.

Then there's the issue of ABS and ASR (traction control). An ABS only rear will have a single wheel speed sensor on top of the differential housing. An ABS + ASR rear will have a rear wheel speed sensor on the end of each axle/backing plate.
Great information thank you.

An axle shop gave me a quote of $1100 to change the gears and set up the PCM and speedometer. Good hunk of change to blow on something that really doesn't need to be done.

That's why I've been hunting for an axle out of a Camaro RS or something with a 3.42.

I don't think this is going to happen LOL.

Thanks again.
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Old 08-31-2017, 04:00 PM
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Re: 3.08 to 3.42 axle swap

My 96 camaro V-6 convertible with a manual transmission came stock with a 3.42 rear end and drum brakes, you can probably find one of these in the wrecking yard easily.
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