Does Changing Diff Affect Speedo Reading On R33

[Giveitall]

Hi Guys, sorry for the silly questions but i would like to know if changing diff will affect the speedometer reading on a r33? And another question, how do i know if my diff is not original?

thanks

[blind_elk]

Changing the diff should not affect the speedo, UNLESS the ratio is different.

[Giveitall]

Changing the diff should not affect the speedo, UNLESS the ratio is different.

if the gear ratio is different, does the speedo reading being affected signifcantly?

[Jdfnq]

Correct me if I am wrong, but changing the diff even if the ratio has changed wont make the speedo read incorrectly as it is measured off the output shaft from the gearbox.......

I might be wrong though

[sh@un]

Of course it's gunna be wrong if you change the final drive ratio. The speedo will read the same speed at the same rev-gear settings as it used to, but it wont correspond to the actual roadspeed

Shorter final drive ratio (i.e larger number after change, like 4.11 ---> 4.375) = Lower actual roadspeed than indicated on guage

Taller final drive ratio (i.e smaller number after change, like 4.11 ---> 3.57) = Higher actual roadspeed than indicated on guage

The ratio tells you how many times the pinion turns for each revolution of the crownwheel

Hope this helps

[Jdfnq]

Of course it's gunna be wrong if you change the final drive ratio. The speedo will read the same speed at the same rev-gear settings as it used to, but it wont correspond to the actual roadspeed

Shorter final drive ratio (i.e larger number after change, like 4.11 ---> 4.375) = Lower actual roadspeed than indicated on guage

Taller final drive ratio (i.e smaller number after change, like 4.11 ---> 3.57) = Higher actual roadspeed than indicated on guage

I stand corrected

Thanks

[sh@un]

no worries

[Giveitall]

Of course it's gunna be wrong if you change the final drive ratio. The speedo will read the same speed at the same rev-gear settings as it used to, but it wont correspond to the actual roadspeed

Shorter final drive ratio (i.e larger number after change, like 4.11 ---> 4.375) = Lower actual roadspeed than indicated on guage

Taller final drive ratio (i.e smaller number after change, like 4.11 ---> 3.57) = Higher actual roadspeed than indicated on guage

The ratio tells you how many times the pinion turns for each revolution of the crownwheel

Hope this helps

Thanks Shaun that helps alot, i raise this question because i suspect my diff is not stock. and the actual road speed is slower than what indicated on the gauge. (10km/h slower - was determined by Tom Tom GPS)

how do i know if my diff isnt stock?

cheers

[sh@un]

A chassis dyno will be able to tell you what percentage speedo error you may have fairly accurately- get the operator to set the roller speed to 100km/h and see what your speedo reads, then again at 150 or so. You can then work out what % it reads over or under the actual speed.

Somewhere on this site, you should be able to find out various ratios, but some i know are-

R32 GT-R (GTS-t too?) - 4.11:1

GTS4 - 4.375.