c4 with 2.80's
 

I was wondering if anyone can confirm this.

66 mustang 2.80 ring and pinion. stock c4.

with 2.80's and 3rd gear in a c4 is 1:1 ratio. with this combo my top speed would be 166 mph. My friend said that that wouldnt sell anyone this combo back then so what they did was they would change the third gear to a lower ratio so it would lower your top speed. i was wondering this because with my old 2.80's at 5,000rpm im at about 85. i was planning on going with 3.73 and didnt want to lower my top speed any more then that. i still want to drive freeway. so if this makes any sense to anyone please let me know. if i gave you numbers off the c4 could that tell you anything and if so where are they located?

I don't know about the top speed but, in 66' if you had a C-4 your and had a type I transmisson your first gear would be 2.46, Second 1.46 and final of a direct drive. On a Type II first would be 2.40, second 1.47 and a final also of a direct drive.

If you go to the software section to the left of your screen you can download drag math which has the calculator for ding that. I would need your tire diameter to figure it out for you. It will be under selection I in the program.

Tranny slipping
 

If you're turning 5000 RPM at 85 MPH in 3rd gear with a C-4 and a .280 axle, then the trans is slipping.

Rev

Unless it's an overdrive tranny, otherwise top gear on most trannys is direct 1-1. 2.80 gear@85mph and 5000 rpm's = a slipping tranny. rpm's should be around 3000-3200 depending on tire size.

No OD's
 

No stock C-4 overdrives.

Rev

it if where my third gear clutches then when im on the freeway and i punch it i would hear the gears winding up with no power but right now i know ahat i want.

it if where my third gear clutches then when im on the freeway and i punch it i would hear the gears winding up with no power but when i do that the car goes as if everything were ok..thats why i thought this was a ratio problem. le me no
.

2.80?
 

Are you sure it's a 2.80? If it was a 4.11, it would do about as you are saying without any slipping.

Rev

im pretty sure they are 2.80's
i just recently took apart my diff. for a rebuild and so i will count the ring and pinion teeth.

pinion has 15 teeth and ring has 42.

15 devided by 42 = 2.80

yeah so im sure there 2.80's

My '66 had the same combo as u, and I could go 130 before I hit 5,500. That was with 185 70R14 tires. I put on 225 70R14 tires, and it changed to about 130 at 4,500rpm.

i know my spedo's off but could it be off that much.
im sure its the stock spedo and now i have 225 60 r15's on it.

at 5000 is says im going 85. could i really be going 100+?

anyone know of a converter to find out what my speed is

also whats the stock tire size..i know its 14 inch rims but what tire size??

Tire size
 

Stock tire size on the '66 was bias ply 6.70/14.

Rev

Speedo is way off. 5000 rpm's with 2.80 gears is around 135-140!

Back to your original question about going over 160 in a stock mustang - no way. The high air resistance of these cars would require more power than the engine could produce. In other words, you can not wind the motor to a high enough rpm to reach this speed.
If you want to estimate the error in your speedometer, measure the time it takes to go a mile while your speedometer is indicating 60 mph. If it takes less than 60 seconds, your speedometer is reading high. There are mile markers, little green number signs, on the side of interstates that you can use as a measured mile.

When I was starting my 6 speed swap I made a program to make RPM/MPH/Gear charts so I can figure out what setup is best for me. I have made you a few in html format and linked them to my webspace. Print them out and compare the RPM required to go a specific speed in a specific gear. Note- the charts show 6 gears, but I made gears 3,4,5, & 6 all 1:1. Click on the links below

C4 with 280 gears
C4 with 355 gears

C4 with 373 gears

C4 with 411 gears