I actually wasn't sure where to post this.......it's kind of PCM related........it's also rather Drivetrain releated.......

Oh well.

As the title states - how much and in what direction will my speedometer and odometer be altered and in which direction when going from 3.42's to 4.10's?

 

the speedo will read high, possibly as much as reading 90 when you are doing 65, so your odo will rack up miles quicker then normal, I went from 2.72s to 3.73s in my old IROC, and it would hit the speed limiter(110mph) at somewhere near 65-70mph

 

Good to know......thanks.

I was rather hoping it wouldn't be all the much, but seeing as how it may effect it a lot - I'm going to send my PCM away to Ion for a re-zappin.

 

The error can be calculated from the gear ratios:

4.10 / 3.42 = 1.20

Speedo will read 20% higher than actual speed.... e.g. - read 72mph at a true 60mph, 96mph at a true 80mph, 120mph at a true 100mph.

Other thing to consider is the affect on the odometer. When you drive 1,000 miles, your odo will rack up 1,200 miles.

 

Gee........there's a way to keep the K off a car.

If going on a long trip and have a PCM that is calibrated for 4.10's - switch them out for 2.73's for the extra milage and the less K on the odometer.

The added cost of the switch would heavily outweigh the savings though.

Just thinking of the possibilities.

Thanks Injuneer.

 

I believe odometer fraud is a felony, with up to 7 years of prison...

 

True, I am sure it is a crime in most (if not all) states. But that would be only if you claimed or implied the oddo was accurate for the purposes of selling the car. IOW, you can sell a car with a non-working oddometer, but there is usually a form or a place on the title where you need to certify that it is not accurate.

Rich