All Small Six C4 Gear Vendor overdrive

[beanmiester]

With the final overdrive gear ratio of .78 it would be at 2400 rpm at 75 mph. I feel like that is a bit better of an improvement

 

[bmbm40]

Just my opinion but if the GV od will do that it is very acceptable. Plus for performance you get 6 forward gears. That video shows what is possible.

 

[Rod Beauvex]

Here is one of those calculators mentioned earlier. You will need to know your tire diameter though.

Spicer Transmission Ratio RPM Calculator

Use the Spicer Transmission Ratio RPM Calculator to determine your engine’s RPM based on the transmission gear ratio, tire height, MPH, and ring and pinion gear ratio.

spicerparts.com

 

[DON]

With the final overdrive gear ratio of .78 it would be at 2400 rpm at 75 mph. I feel like that is a bit better of an improvement

300 to 350 rpm difference at 75 mph? To me that doesn’t seem like much improvement for the cost in parts and labor. If it was 800 to 1000, that might be a different story.
This is one reason I will be going with a 8in rear axel- gear options.

 

[powerband]

cool calculator' for instance
'63 Falcon wagon 170 six / T5 - .68 OD (V8 GT) / 3.50 rear / Michelin 215-70-14's (25.9' tire height - 802 revs' per mile)
.
2000 RPM = 65 MPH
.
2200 RPM = 71 MPH
.
2305 RPM = 75 MPH
.
.
have fun

 

[beanmiester]

300 to 350 rpm difference at 75 mph? To me that doesn’t seem like much improvement for the cost in parts and labor. If it was 800 to 1000, that might be a different story.
This is one reason I will be going with a 8in rear axel- gear options.

I was going to change the rearend too but I don't quite know to what. Mist of the recommendations I see are for performance cars not little puttering around cars

 

[drag-200stang]

What I got with the Spicer calculator is, RPM 6,800, tire 33'' gear ratio 4.86 = 137.42 .
That is also what I saw on tach and E.T. slip.

 

[beanmiester]

300 to 350 rpm difference at 75 mph? To me that doesn’t seem like much improvement for the cost in parts and labor. If it was 800 to 1000, that might be a different story.
This is one reason I will be going with a 8in rear axel- gear options.

Oh actually I just looked at it. Its like a 600 rpm difference. Sock its at 3100. With the final overdrive its 2419

 

[DON]

I was looking at post #21 and #20. They may not be figuring the same speeds.

 

[beanmiester]

Yeah they are. I just realized that might have been confusing. Sorry

 

[Frank]

2742 still too high?

What is the need for driving so dangerously fast? Slowing down will lower the rpm into a sane region, and recreate the chance of surviving a crash. ??

 

[beanmiester]

Interstate. They pull you off if you go 6 mph below the speed limit near downtown Tucson. Which i have to pass by if im to go anywhere in a timely manner. Its 75 mph there now. I got my car to stop very well so if I keep good following distance I should be fine