RPMs are so high!!

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04-07-2006, 07:02 PM

#11

gspfunk

5th Gear Member

Join Date: Nov 2004

Location: Texas

Posts: 3,834

RE: RPMs are so high!!

He needs to measure the diameter of his tire from tread to tread. Is that what you meant?

If it's a different diameter than stock, that will throw your speedo off regardless of your speedo gear.

04-07-2006, 07:55 PM

#12

sc94gt

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Join Date: Jul 2004

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Posts: 501

RE: RPMs are so high!!

At 3000 rpm I am at exactly 90 mph with my 3.73's.

04-07-2006, 08:05 PM

#13

Tims 88GT

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RE: RPMs are so high!!

his tires look a lot smaller than stock. yes i ment tread to tread. thanks for clarifying that

04-07-2006, 08:17 PM

#14

89gtsleeper

2nd Gear Member

Join Date: Apr 2006

Posts: 335

RE: RPMs are so high!!

maybe I missed something, but what trans are you using.... If it's a c4, then the rpms will definitely be higher... I drive a TKO with 3.73's and I pull about 3000 at 90mph

04-07-2006, 10:12 PM

#15

uedlose

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Join Date: Jun 2004

Location: Charles Town WV

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RE: RPMs are so high!!

gears are measured at a set tire size and that is 26 in so if your tire is smaller then 26in tall then the ratio goes up if it is taller the it goes down. in short bus terms 355 are only 355 with a 26in tall tire. your tire size is below that your motor will spin faster then a motor with a taller tire. MOST 225- 60- 15 stock size 15in tires are just around 26 tall. get a tape and go look. While you are out get us a beer.[sm=icon_cheers.gif]

04-07-2006, 11:12 PM

#16

AdderMk2

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RE: RPMs are so high!!

Quote:

ORIGINAL: uedlose

MOST 225- 60- 15 stock size 15in tires are just around 26 tall. get a tape and go look.

25.6" actually

Quote:

ORIGINAL: Twisted

As I mentioned in my other post, I just got 3.55s installed today. I just now went out and beat on the car a bit. Wow!! Huge difference!! At any rate, I took the car on the highway, and at an indicated 70mph, it seems like I was awfully close to 3k rpms. Not only that, it felt like I was actually going faster than 70mph. I'm starting to wonder whether the shop installed the correct speedo gear. Anyway, my questions are:
1. Do these rpms seem normal for 3.55s?
2. I'm driving across the country in a few months. Can my 302 handle those rpms for 3k miles?

1. no. at 80 mph you should be at 2500 rpms with a t-5 manual in 5th gear
2. probably wouldnt hurt to not drive so damn fast

here are a few questions i have for you....
Did the installer change out your speedometer gear?
If so, which one was installed?

04-08-2006, 02:07 AM

#17

Twisted

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Join Date: Feb 2006

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RE: RPMs are so high!!

Quote:

ORIGINAL: AdderMk2

Quote:

ORIGINAL: uedlose

MOST 225- 60- 15 stock size 15in tires are just around 26 tall. get a tape and go look.

25.6" actually

Quote:

Thanks for the replies, everyone. I was able to get the problem solved. He put in a 23 tooth gear, thinking I had the 6 tooth tranny gear. He put in a black 20 tooth, and the speedo seems to be correct now. My tires are a bit small so now, at 75, I'm just a little below 2500 rpms. Good enough, until I can get some tires. Although, honestly, I'm enjoying the acceleration of the smaller tires. They just look funny though.

04-08-2006, 02:20 AM

#18

Tims 88GT

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Join Date: Jan 2005

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RE: RPMs are so high!!

u know u need a 23 tooth right?

04-08-2006, 02:36 AM

#19

Twisted

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RE: RPMs are so high!!

Quote:

ORIGINAL: Tims 88GT

u know u need a 23 tooth right?

Really? That's what I had, and the speedo was way off. It feels correct with the 20 tooth, black gear. Maybe I'm not remembering correctly whether I have a 6 or 7 tooth tranny gear.