kevin2392

i have a c4 3-speed auto...what gear ratio would be equivalent to a 4.10 for a 5-speed?

1971mach1

Not understanding the question.
Do you want to put in a 5-speed?
Or do you want the equivelent gearing of a 5-speed (with 4:10 rear) in 5th gear?
Or 1st gear?
Which model 5-speed? ,they have different ratios.

kevin2392

im not looking to put in a 5 speed (yet) but say a t-5 with 4.10 gears in it...what size gears would i need in my 3 speed that would make it about the same acceleration as the t-5 with 4.10 in low gears?

Gun Jam

c4 1st 2.46:1
t5 WC 1st 3.35:1

t5 wc with 3.35 1st and 4:10 = 30mph @ 5500
c4 with 2.46 1st requires 5:70 for 30 mph at 5500 all other variables constant.

So as you guessed dont mess with gears until you get your t5 done. If you must then 3.55 is a LOW as you can practically go with c4 and still drive it. 3.00 is a better choice. 4.11s would be murder

-Gun

musnicki

Use this tool that was posted like 5 years ago for me asking a similar question when I switched from a three speed to a five speed:

http://www.5speedtransmissions.com/gear_calculator.html


From Thailand!!!

James

smitten

Great calculator as it also includes SLR which gives a good idea of what acceleration to expect and, in turn, how useful first gear will be with a 5 or 6 speed as well as what the OD RPM's will be. Nice complete picture in one calc.

lthawthorne

You need to set tire size and select the transmission (esp. the overdrive ratio), the last thing to pick is rear end ratio.

I have an AOD, originally had 3.7 rear gear on a peg leg, all smoke no go; ran about 2200 rpm at 70 mph with the tires (28"?). I replaced differential with a built Currie 3.5 ratio Detroit True Trac limited slip. Cruise speed is now 2000 rpm at 70 mph. For a daily driver like mine the engine speed needs to be low enough for good economy and longevity, but high enough that car can leap ahead to pass but also not cause the converter lockup to hunt when you drop to 40-45 mph, which mine does once in a while. The original 3.0 gear on an FMX and original tires/wheels ran about 2650 rpm at 70.