S13 RB25DET 70MPH @ 3700 RPMs ??

[S13RB25DETDRIFTER]

ok i notice that my car when i go at 70MPH its at a high RPMs 3700
now i have a 5 speed manual transmission on my rb25det and i have a VLSD from a R32 skyline 5 bolts axles now can it be because i have a high gear rear end ???

[datsunnazi]

you probably have a 4.36:1 rear differential from an R32 GTR. It would cause you to have a very high cruising speed. I had one in my S13 with an RB20 and it was exactly the same.

[S13RB25DETDRIFTER]

ok sounds about right now this is my daily car you know any differentials that are 5 bolts with lower ratio i waste alot of gas with this one

[titangts]

get the older style 94 and below J30 rear end..will bolt right in. you'll just need to change the rear diff cover to your s13 one. the axles should be same considering its 5 bolt. but it wouldnt hurt to buy a 5 bolt j30 diff with the axles that belong to it.

it'l drop your rpm at 70mph to about 3000

[S13RB25DETDRIFTER]

Ok well what if I just used the ring gear and pinion from j30 because I heard that the j30 diff has that extra inch for the driveshaft?

[fullthrottle]

Ok well what if I just used the ring gear and pinion from j30 because I heard that the j30 diff has that extra inch for the driveshaft?

That would be even harder than just swapping the diff and axles...

[jholman]

That would be even harder than just swapping the diff and axles...

agreed too much work

[shahabshaukat]

a 4.36:1 would cause your speedo to read higher than your actual speed meaning you would reach 70 at a lower RPM. make sure that your actually doing 70 when your speedo says so, I think you may actually have a lower ratio rear end which would cause the speedo to read like 70 when your actually doing 80 or so. Your speed sensor is in the transmission and does not take into consideration the ratio of your diff.

[S13RB25DETDRIFTER]

i used my phone GPS and check speed and i was doing 70MPH at those RPMs