[dark7068]

Howdy, I changed my rear gears in the Fairlane to 3.55 from 2.79 I finally got a good hi-way blast today, and had no problem burrying the speedo (120mph). I also have the original C4 totally rebuilt with stage 2 shift kit, and 350 hp 289. It also has the original speedo cable (cant remeber count on gear or color) and the calculators say I'm 16mph off. What color and gear tooth count will correct this. It also has 215/70/15 tires and reved around 3800 rpm at 120mph.
What a blast, the wife was checking the tach and the speedo for me.
Time for an AOD I think.

Thanx

Rick

 

[tricky]

I nead to now the outside diameter of the rear tires. Then I can tell you the gear you nead.

 

[dark7068]

The tire is 25.85 diameter, according to a tire calculator. I mentioned it above as a 215/70/14.

Thanx

 

[Jimmys66]

Here is the formula but you'll need the driven tooth count.

# of drive gear teeth x axle ratio x tire revolution per mile divided by 1000.

Tire revs per mile = 63360/tire OD in inches x 3.1416.
Good Luck.

 

[Mattstang65]

try this website for sppedo gear calculations. Also, the 215/70/15 tire calculates out to @ 26.8 inches tall. http://www.randysringandpinion.com/gear/g0598.html

 

[Eldoon]

Hey, Dark!

I didn't know there was a highway near Kamloops with a 120 mph speed limit!

And imagine having your better half aboard, taking the risk of leaving your kids and boxers as orphans!

Revving 3800 @ 120+ with a stock C-4? What is it revving at 60? I'm considering a 3.55 gearset someday myself.

Eldoon of the Mounted (NOT Highway Patrol!)

<font size=-1>[ This Message was edited by: Eldoon on 2/18/02 12:26am ]</font>

<font size=-1>[ This Message was edited by: Eldoon on 2/18/02 12:33am ]</font>

 

[andwrong]

3800rpm @120 with the new gears???? wow... i swear my mav with the stock c4 and the 2.79s was doing more rpms than that at 115...

 

[luebben]

There is no way you were even close to doing 120 with that RPM. That might have been what the speedo said but it was way off.

 

[luebben]

With the 215/70/14 tires and 3.55 gears and no overdrive I calculate your true speed at 3830 rpm to be 83 mph.

 

[dark7068]

Eldoon, there isnt a hi-way that lets you go that fast. But what the F... right. It was a nice day, kids werent in the car.
I took pictures today of it, they are hard to see the dials, but the speedo is at 120mph, and the tach is at 4000rpm. Look hard.

Rick

I know my speedo is off, that's why I ask my question.

_________________

68 Fairlane/70 Cougar

<font size=-1>[ This Message was edited by: dark7068 on 2/18/02 8:12am ]</font>

 

[Eldoon]

Sorry, Rick...I couldn't resist a little dig. Just my evil nature showing through!

 

[dark7068]

BAD COP, NO DONUT!!!