RB26 with RB25DET gearbox - what R200 diff ratio

[Mike Rowe]

I ran some calcs tonite on the current diff which is in the Z - 3.7 and came up with ludicrous speeds ie 351km in 5th gear @ 8000rpm - even with wind resistance and pulling lower revs still a little high dont you think?!!

It almost looks like I have to go 4.375 or 4.1 at lowest. What have others used?

regards

Gear speeds 3.7diff.txt

Gear speeds 3.9diff.txt

Gear speeds 4.1diff.txt

Gear speeds 4.375diff.txt

[RB26powered74zcar]

I'm using a 3:7 VLSD right now and it does tend to need more gear. I'm going to try a 3:9 CLSD shortly, then go to a 4:11 CLSD I have if need be...

 

Nice graphs

I wish that was all in imperial values

[Kennysgreen280zt]

You could use this and enter in the RB gear ratios. all the fields are modifiable. http://www.geocities.com/z_design_studio/transmission.html

[Canadianz]

Hi Mike,

 

Yeah I definatly agree with you the speed you can get out of a RB + R200 is pretty amusing. If the car is going to be a DD then I wouldn't go with the 4.11's or so. Im running whatever the stock R-180 I think its stupid high. I can do probably over 170 km/h in 3rd gear. (GPS calibrated Autometer Speedo) While it definatly hurts performance, the car is a dream to drive on the highway as it is pulling about 2200 RPM at 120km/h or about 70-75 mph. I also get rediculus fuel economy too because the revs are so low. Still though I can drop down to 3rd and mat it and it goes like hell. If it is a drag or track car definatly look for something a bit lower though, Fenton_fury who posts on here is running 4.11's I belive and really likes them. I'm on the look out for a slightly lower set as I do want a bit more acceleration, however the car is still really quick and fun to drive even though it is geared a bit tall.

 

So I suppose it all goes for what the car is used for.

 

Thats my experiences for an RB25det with the RB25 Tranny..

 

Chris Crombie

[stony]

If i remember my original diff in the red car was a 3.7 and i was getting 127mph near the top of 3rd going thru the traps.

 

i got my hands on a 4.88 aftermarket diff that i was actually able to get into 5th but only got down the track once without breaking something.

 

 

But yes with the rb25 tranny you will get stupid hi speeds if you could actually get the car to go that fast. It does make for really good cruising rpms!!!

[zilvia_gt]

Why wouldn't you want 4.11's for daily driving? Don't the skylines come with 4.11 stock?

 

Hi Mike,

 

Yeah I definatly agree with you the speed you can get out of a RB + R200 is pretty amusing. If the car is going to be a DD then I wouldn't go with the 4.11's or so....Fenton_fury who posts on here is running 4.11's I belive and really likes them. I'm on the look out for a slightly lower set as I do want a bit more acceleration, however the car is still really quick and fun to drive even though it is geared a bit tall.

[Mike Rowe]

Yes that is the confuser, in that the GTR is 4.11, but their gearbox ratios are different.

It also looks slightly better with 225/50/16 rather than the 225/55 I used in the graph which actually was incorrect. When I looked at the 100kph speed in 5th with the 3.7 its actually about right around 2100rpm so maybe it will be ok. I do want to have a good standing qtr time though so will have to be in the middle somewhere maybe the 3.9.

 

Joel if you go to this link you can get the graph in imperial as well, just tick the imperial box http://locost7.info/gearcalc.php

 

regards