Looking for advice on my "new" wrong RPM diff?
Thread Starter
Pro
Joined: Jun 2008
Posts: 575
Likes: 10
From: Oskaloosa Iowa
Wow lots of posts! - I never slammed RPM, I was just saying if i come to the conclusion that it does have the wrong ratio then i'll be pissed, anyway.
I called TJ at RPM and he said the samething that the Vettes don't need to be callibrated so thats solved, he also said i am correct about the rpms are 3400 in 4th and i now need to do a test in my dads stock 3.42 C5, it should be about 3000 at 70 in 4th. So it looks like i might have a 3.90 after all. He said when we did the test in 6th at 70 it'd be very hard to see any rpm difference cuz of the amount of overdrive in our cars.
I'll give it a whirl tonight and i'll report back. Thanks!
I called TJ at RPM and he said the samething that the Vettes don't need to be callibrated so thats solved, he also said i am correct about the rpms are 3400 in 4th and i now need to do a test in my dads stock 3.42 C5, it should be about 3000 at 70 in 4th. So it looks like i might have a 3.90 after all. He said when we did the test in 6th at 70 it'd be very hard to see any rpm difference cuz of the amount of overdrive in our cars.
I'll give it a whirl tonight and i'll report back. Thanks!
Tech Contributor
Joined: Jan 2007
Posts: 19,448
Likes: 1,155
From: Dyer, IN
Drifting
Joined: Feb 2006
Posts: 1,585
Likes: 15
From: New Hartford IA
Wow lots of posts! - I never slammed RPM, I was just saying if i come to the conclusion that it does have the wrong ratio then i'll be pissed, anyway.
I called TJ at RPM and he said the samething that the Vettes don't need to be callibrated so thats solved, he also said i am correct about the rpms are 3400 in 4th and i now need to do a test in my dads stock 3.42 C5, it should be about 3000 at 70 in 4th. So it looks like i might have a 3.90 after all. He said when we did the test in 6th at 70 it'd be very hard to see any rpm difference cuz of the amount of overdrive in our cars.
I'll give it a whirl tonight and i'll report back. Thanks!
I called TJ at RPM and he said the samething that the Vettes don't need to be callibrated so thats solved, he also said i am correct about the rpms are 3400 in 4th and i now need to do a test in my dads stock 3.42 C5, it should be about 3000 at 70 in 4th. So it looks like i might have a 3.90 after all. He said when we did the test in 6th at 70 it'd be very hard to see any rpm difference cuz of the amount of overdrive in our cars.
I'll give it a whirl tonight and i'll report back. Thanks!
Thats not right as I've had both a m12 and m6 in my z with 3.90's and it's 2000 vs 1800. It's fairly easy to tell. We had the same mixup on the dyno with my car and the 3.90's. Best thing to do is leave it on the 3.42 gear size and adjust the tire size (if you run something other than stock) till the speedo matches the dyno speed.
Last edited by slow ride; May 24, 2010 at 05:32 PM.
Thread Starter
Pro
Joined: Jun 2008
Posts: 575
Likes: 10
From: Oskaloosa Iowa
Here's the deal, its a 3.90 I did the test that RPM suggested in 4th gear and did the same to my dads and mine is 3400 at 70 and his is 3100 at 70 so we are good to go..... I'm calling RPM tomorrow and telling them there are no problems just a little confusion. I'm extremely relieved now.
Either way thanks to the ones that was helping me diagnose the issues even though it looks like its caused more issues than solved for some..... sorry to get anyone wound up!
Case closed
Either way thanks to the ones that was helping me diagnose the issues even though it looks like its caused more issues than solved for some..... sorry to get anyone wound up!
Case closed
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
Here's the deal, its a 3.90 I did the test that RPM suggested in 4th gear and did the same to my dads and mine is 3400 at 70 and his is 3100 at 70 so we are good to go..... I'm calling RPM tomorrow and telling them there are no problems just a little confusion. I'm extremely relieved now.
Either way thanks to the ones that was helping me diagnose the issues even though it looks like its caused more issues than solved for some..... sorry to get anyone wound up!
Case closed
Either way thanks to the ones that was helping me diagnose the issues even though it looks like its caused more issues than solved for some..... sorry to get anyone wound up!
Case closed
No one is really wound up, it's how you phrase your words that incite others responses to you.
Just thing about what you're saying or writing.
I'm glad you got it all sorted out.
Melting Slicks
Joined: Jun 2005
Posts: 2,396
Likes: 52
From: Sicamous BC
If HPT was used for calibrating it will changed the speedo when doing the new gear calculations.
You just have to change the speedo back to it's original number.
That has caught many of us.
You just have to change the speedo back to it's original number.
That has caught many of us.
