No 1st gear on 4th Gen auto!?

[PaycekZ28]

Originally Posted by HorsePowerAddicts

Holding it in first while driving around will just heat the trans up. Its best to leave the car in drive and have your shift points set to match your setup.

No, I'm not gonna drive around in first. I've just never been able to select 1st and it was kinda annoying. Plus it got me about an hour away from wife

[xsofa]

I spy a penny

[Revo1]

Originally Posted by PaycekZ28

I have a '97 Z28 auto, and I only have 2nd through OD. What gives? I've owned the car for over a decade and still have no idea why no 1st. Any info would be awesome, thanks!

My 96 was the same, but my 02 has 1st gear on the shifter. Not sure why that is...

[zebra]

Originally Posted by fbodyrs96

GU2
This is the standard axle ratio for an automatic Z28. The ratio is 2.73.

With this axle ratio, you do not have 1st gear as a selectable option on your shift plate.



This is due to federal noise pollution regulations GM had to conform to. Cars with RPO GU5 have 1st gear, because their 3.23 ratio made 1st gear impossible to select. Why? Because the speed was too high for a 3.23 Z28 to run in 1st gear, but not too high for a 2.73 Z28 to run. The 2.73 Z28s would be too loud (high in RPM) to pass the test in first gear, so GM had to restrict it.

I don't remember the 4-speed automatic gear ratios off the top of my head, so I can't tell you what speed the test was testing, but I would "assume" it was 45 mph. 3.23 axle would likely cause the max speed in 1st to be closer to 40, while 2.73 would likely cause the max speed in 1st to be closer to 50. I need somebody to do the math...

if it's standard 4L60e gearing, it'd be
3.06 - 1.63 - 1.00 - 0.70

combine 1st gear with 245/50-16 tires and you get:
2.73 rear - 55mph @ 6000rpm, 45mph @ 4927rpm
3.23 rear - 46mph @ 6000rpm

[Revo1]

Originally Posted by PaycekZ28

No, I'm not gonna drive around in first. I've just never been able to select 1st and it was kinda annoying. Plus it got me about an hour away from wife