ZR-1 Net Registry Forums - View Single Post - A question about speed reading at 5th gear

gorgeousgeorge · 11-13-2010

Hi.
I would like to thank everyone who responded to this thread. I inspected the ratio of my rear end today and found the propeller shaft rotate 3 and about a half turn while rear tire making complete 1 turn. I believe the final ratio is 3.45, i.e. stock.

I did the inspection at my friend mechanic?s shop. My friend mechanic was under my ZR-1 and was counting the number of rotation.

I concluded that the tachometer is inaccurate.

DOES THIS OFTEN HAPPEN TO C4s?

How could I do to fix this problem?

When the GPS meter read 223.9km/h(=140MPH), my inaccurate tachometer read 7000 rpm. The true rpm will be around 5200 to 5400 rpm, if the true speed of 7000 rpm in 5th gear is around 180MPH to 200MPH.

I am wondering what to do next

By the way, I talked with my friend mechanic about how we should improve our Corvettes till 10 oclock at night

Yoshi Honda
1991 ZR-1

11-13-2010	#11
gorgeousgeorge Join Date: Nov 2010 Location: Japan Posts: 30	Re: A question about speed reading at 5th gear Hi. I would like to thank everyone who responded to this thread. I inspected the ratio of my rear end today and found the propeller shaft rotate 3 and about a half turn while rear tire making complete 1 turn. I believe the final ratio is 3.45, i.e. stock. I did the inspection at my friend mechanic?s shop. My friend mechanic was under my ZR-1 and was counting the number of rotation. I concluded that the tachometer is inaccurate. DOES THIS OFTEN HAPPEN TO C4s? How could I do to fix this problem? When the GPS meter read 223.9km/h(=140MPH), my inaccurate tachometer read 7000 rpm. The true rpm will be around 5200 to 5400 rpm, if the true speed of 7000 rpm in 5th gear is around 180MPH to 200MPH. I am wondering what to do next By the way, I talked with my friend mechanic about how we should improve our Corvettes till 10 oclock at night Yoshi Honda 1991 ZR-1