U7198
Revision 9r15
2002 Chevy Camaro SS 6 speed manual


Hello, I just got a diablo predator and I'm having issues getting my speedometer corrected with the Proper gear ratio (3.73)

I purchased my 2002 camaro SS a few years back, lived with the speedometer off 4+Mph @70, so I drove 66MPH to achieve 70 via correction from GPS hand held unit and a nice speeding ticket back in 08.

I figured the previous owner put in 3.73's and I decided to set the predator to correct it. At first, the car was a different animal, but quickly realized that I was going faster than everyone else. Checked RPM and MPH on fbody.org/gears and found out it was off. Next, I grab my trusty old GPS unit again, and go for a spin and sure enough, I’m off by 6.6MPH (60MPH was really 66.6MPH). I then set the unit for 3.55, still off, 3.42 was still off. I reluctantly set it for 3.27 (3.23) gear ratio and the GPS matched up nicely with my speedometer. Great, now what!! BTW, I left tire size stock 275/40/17

Now here’s the kicker, I go back to fbody.org/gears for reference and when I put in 3.27, everything is off, but if I set the gear ratio for 3.42, "their calculator" has me at 1600RPM @ 70, which is exactly what my speedometer/tach reads. What am I doing wrong? Currently, my speedometer is spot on, but like I said, I have the predator telling the ECU I have 3.27’s. I'm confused…………what I want is matched GPS speed with my speedometer for 3.73's @ 70Mph & 1700RPM

P.S...The 3.73 setting really woke up the car. Setting it to 3.27, I really don't notice anything. I don't know what that A/F ratio setting was, but I really felt the car was faster under the 3.73 settings.

Any insight would be much a appreciated.

 

I'm sorry to answer your question with a question but what size are your tires? This has much to do with your speedo / tach numbers.

 

My stock Tire size is 275/40/17....I set the predator for that size as well.

all I want is my MPH to match my speedometer w/3.73s which should be 1700RPM @ 70 if I’m not mistaken.

P.S....I hate to assume, but if my speedometer was off originally by 4MPH+ @ 65, then this must mean the original owner changed rear gears ratios (3.42 to 3.73's)... right?

BTW, when programmed for the 3.73's, the car ran like a raped ape! Too bad the speedometer was inaccurate!!!!

 

I had the same problem with my 01 Trans Am, GPS, and Predator. It tuned out to be the GPS. If my math is right your car still has the factory 3.42 gears. So set the Predator to 3.42 and be done with it. The older GPS units are know to be off by about 3 mph. BTW changing the gear settings has NOTHING to do with performance, that is based on the Predator box tune or a custom Predator tune.

 

If it is stock geared and stock tired, reset all parameters and check it again, should be fine.

If you are unsure about the gears, get under the car and spin the tire on revolution, and count how many times the DS spins, if it is less than 3.5 revolutions, its a 3.42, if it goes around more than 3.5 times, probably 3.73...

 

Hey thanks a million for everyones insight on this. I'm beginning to think i really do have 3.27's instead of the 3.73's originally, since I was going faster then the speedo leads me to believe (4+), the orginal owner must have broken the 3.42's.

When it stops raining here, I will raise the rearend and mark the DS & wheel and rotate it to confirm the ratio.

 

O.K, I raised the rear-end of the car off the ground. Marked the wheel and rotated it "one full rotation" and the Drive shaft only went around less the 2 times!!!!

What am I doing wrong??

The transmission was in neutral. dam this, we have a storm moving in tomorrow!!!

 

Make sure both wheels were spinning?

Something ain't right....

 

Mike thanks for quick reply...

Ya, both wheels are moving, other wheel rotated in opposite direction (posi)

I'm stumped....