Formula for Ratio working out

[TOYrantula]

Alrighty....
I had a 4cyl with 4.8's and 35's, on the highway at approx 3000rpm, I was doing 110kph.
What is the formula to work out the gear ratio so that on they highway doing 110kph, I'm revving at about 2200-2400rpm.


Thanks,
Damien

[Dozoor]

Toy need to know your fifth gear ratio it isn't 1.1 so it will make a difference . I assume luxs have a 1.1 ratio on the transfer for two wheel drive mode ?

Just as a matter of interest are you gearing it for an engine conversion ?

[NICK]

the ratio is fit 37mtrs and it will be sweet.



NICK

[Bush65]

4.8 x 2200rpm/3000rpm

[TOYrantula]

I dont have enough lift for 37's

Bush65: You could have worked it out for me but according to your formula.... I would need 3.5

Dozoor: Hang on....just running to garage to look at manual...brb....phew, took awhile to find it. 5th is 0.851:1.
Already done engine conversion, 4.3L Chev V6. Just screaming to much on highway and running out of revs when dragging but if change ratio's...I will lose my awesome take-off

[Dozoor]

A 4.1 = 2300rpm @ 110ks, 4.3 =2415rpm @ 110.

At the moment at 3000rpm you are actually doing around 120ks

RPM = kmh divided by 1.6 x gear ratio x 336 divided by the tire diamater.

just remember the gear ratio is the final ratio so if it has an overdrive for top gear you have to x the top gear ratio by the diff ratio to come up with your ratio input.

Is this right

[ALPINE-OFF-ROAD]

well im going to add my 2 cents worth

well 4 or 5 speed it dont realy matter ok
coz most 4th gears are 1 to 1 and fiths are below 1 in other words an over drive

these specs are worked out asuming 1 to 1 in 4th gear ( less rpm if a 5 spd box) ok at 65 miles per hr (110 ks hr????)

with 35 inch rubber

rpm....gears
2134=3.42
2215=3.55
2328=3.73
2440=3.91

good hyw legs 35,s 2565rpm=4.11
back to std gearing 35,s 2845rpm=4.56
more power 35,s 3201rpm=5.13

rule of thumb ratio guide

.12 x38 (tire size) =4.56 gears

hope some of this dribble helps ya