Diff ratios?

rb_slider, Aug 17, 3:44pm
can someone please tell me how the ratios work, im looking at 2 different diffs one is 4.1 and the other is 4.3, current diff in car is a r200 with 4.1 ratio, would 4.3 make it rev out higher while driving!
jmma, Aug 17, 3:58pm
Maybe (o:
rob_man, Aug 17, 4:02pm
If you change to the 4.3:1 it will rev higher at a given speed than the 4.1:1.
wsnownz, Aug 17, 4:04pm
.but the vtec will give it more power so it won't need to.
falcon15, Aug 17, 4:07pm
yes a 4.3 will make it rev higher than the 4.1 diff at the same speed
wsnownz, Aug 17, 4:10pm
gaaaaay
unclejake, Aug 17, 4:12pm
Correct
lookoutas, Aug 17, 4:39pm
Just as well there's some people with clues on here.
petermcg, Aug 17, 4:50pm
This is correct, it will also put the speedo out,but give the car a bit more acceleration, and should be slower up top at the same max revs,, but as in some cases where the car may of had to tall a gearing to start with, this change could make the car go faster, but would need to use a lot more revs to do it.
yudasgoat2000, Aug 17, 7:12pm
Provided the speedo drive is connected to the driveshaft, and not one of the hubs.

If the speedo drive is hub-mounted, it will only read false if the wheel rolling circumference is changed.

Likewise with the odometer.
unclejake, Aug 17, 7:27pm
What common vehicles have hub mounted speedos!

It isn't something I have seen, but I am not a mechanic
rb_slider, Aug 17, 7:31pm
ok so il go 4.1 or maybe even 4.0 if i find one.
motorboy2011, Aug 17, 7:36pm
assume it a nissan! just get the speedo drove from the gearbox too.
mrfxit, Aug 17, 7:57pm
HUH!

Not on any domestic vehicles I have ever seen in over 40 years of the auto industry.

Regardless, for there to be no change in speedo, the drive would have to be on the wheel hub or directly off the axle.
Even off the driveshaft end of the gearbox (tail shaft) the drive shaft would be spinning a little faster on the lower geared diff head
mrfxit, Aug 17, 7:59pm
Manufactures muckup, OEM gearing too tall for the engines power rating
falcon15, Aug 17, 8:28pm
if your nissan is rb25det or sr20det powered it should have a 4.08 ratio diff. the ratio is on the chassis tag
clark20, Aug 17, 9:31pm
I think my Dore gets the speed from the rear ABS sensors, so a diff change does not interfere with speed reading
rb_slider, Aug 19, 7:30pm
engine is a rb25det, that explains why it revs so high at 100. cheers falcon15