EF Ian Posted February 2, 2013 Share Posted February 2, 2013 Trying to decide on which ratio diff to use for when I swap in an RB26DETT. Was originally planning on using my stock 3.7 R200 but I now beleive this will be too long. So option are: 3.7 3.9 4.1 4.3 I'm thinking 4.1 would be good as I'll be running at least 400HP, 3.9 would do but still might be slightly too long. What do othesrs think? What are you other guys with RB's running? Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted February 2, 2013 Share Posted February 2, 2013 4:11 R200 GT-R clsd short nose (6 bolt axle) diff for me. That paired up with the RB25det 5 spd trans gives me excellent pull. Quote Link to comment Share on other sites More sharing options...
Wedge Posted February 2, 2013 Share Posted February 2, 2013 ^^ Did you swap that whole thing in the long nose ? What custom axels did you end up using ? Quote Link to comment Share on other sites More sharing options...
stony Posted February 2, 2013 Share Posted February 2, 2013 Drag racing? I had a 4:88 in mine once. Damn near ripped the entire rear suspension out of the car ;> I could only do 130mph at the top end of 5th. Agree with Joel... 4:11 especially if your running the RB25 tranny. Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted February 3, 2013 Share Posted February 3, 2013 ^^ Did you swap that whole thing in the long nose ? What custom axels did you end up using ? I used it like you see it (just put a different larger oil capacity rear cover on it). MM R230 front diff brace, and their 1/2 shaft center bars. I have a few pics in my sig link below... Quote Link to comment Share on other sites More sharing options...
Wedge Posted February 3, 2013 Share Posted February 3, 2013 Thank you ! Quote Link to comment Share on other sites More sharing options...
Wedge Posted March 14, 2013 Share Posted March 14, 2013 What kind of top speed would you see on a stock 280Z 3.5 ? Quote Link to comment Share on other sites More sharing options...
EF Ian Posted March 14, 2013 Author Share Posted March 14, 2013 4:11 R200 GT-R clsd short nose (6 bolt axle) diff for me. That paired up with the RB25det 5 spd trans gives me excellent pull. I've gone for a 4.11 so hopefully it works well for me. Do you find it to be too short at all or is it pretty much spot on? Quote Link to comment Share on other sites More sharing options...
EF Ian Posted March 14, 2013 Author Share Posted March 14, 2013 What kind of top speed would you see on a stock 280Z 3.5 ? Assuming you have an RB26 with 8000rpm redline, 245/45/16 wheels and a stock R33 GTS-T gearbox then it will come down to how much power you have and how good your aero is. Reason I say this is you'll never reach your top geared speed which would be 223mph with the above setup. Quote Link to comment Share on other sites More sharing options...
raven12 Posted March 15, 2013 Share Posted March 15, 2013 Has anyone had a 3.9 and swapped to a 4.11? Quote Link to comment Share on other sites More sharing options...
Wedge Posted March 15, 2013 Share Posted March 15, 2013 Assuming you have an RB26 with 8000rpm redline, 245/45/16 wheels and a stock R33 GTS-T gearbox then it will come down to how much power you have and how good your aero is. Reason I say this is you'll never reach your top geared speed which would be 223mph with the above setup. Thank you I found a speed to gear ratio calculator. 3.54 would be nice but to cruise in 5th gear at 120km/h lower rpm better mpg for a daily hehe. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted March 16, 2013 Share Posted March 16, 2013 Has anyone had a 3.9 and swapped to a 4.11? i have close. I had the stock R230 gears which are 3.69 and swapped out the ring and pinion to a 4.11. The 3.69 was a little tall for around town driving. the 4.11 made a huge difference. with my current setup i could easily hit 180. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted March 18, 2013 Share Posted March 18, 2013 I had a 3.9 and swapped to a 3.7 and I will eventually be going back to a 3.9 as I liked it better for the DD and was a good compromise when I hit the track Quote Link to comment Share on other sites More sharing options...
helghast7 Posted March 18, 2013 Share Posted March 18, 2013 Thank you so much for the info. This is something I had been wondering since theirs a lot of threads talking about diff swaps, but very few talking about specifically for Rb swaps and the ideal ratio. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted March 20, 2013 Share Posted March 20, 2013 Yea i would think a 3.9 would be pretty good. Quote Link to comment Share on other sites More sharing options...
240zdan Posted April 14, 2013 Share Posted April 14, 2013 4.11 gtr clsd is the way to go IMO Quote Link to comment Share on other sites More sharing options...
ZT-R Posted April 16, 2013 Share Posted April 16, 2013 ^ yes on a rb26 it was nice. Quote Link to comment Share on other sites More sharing options...
mtnickel Posted May 23, 2014 Share Posted May 23, 2014 Anyone else have any thoughts on this? I'm running an RB25det and not sure whether to put my LSD carrier into the 3.54 or the 3.90. I'm only running 205/50/16, so perhaps the lower gear is best. Highway cruise would be nice on the tall gear as well. I'm aiming for around 300whp. I'd like to have traction in 2nd if possible. Thoughts and Speeds - 3.54 - 3.90 60mph 2160rpm 2400rpm 70mph - 2500rpm 2800rpm Trap speeds: 3.54 - 113mph @ 7000rpm in 3rd (likely my redline). 3.90 - requires 4th gear 5400 to ~6000rpm (113mph) Quote Link to comment Share on other sites More sharing options...
Vandergriff84 Posted May 23, 2014 Share Posted May 23, 2014 So I am running the stock R180 on my 260z with rb25det and it feels like 5th gear is struggling until I get up to 75mph. I don't plan to be running it above 100mph very offten so I am assuming a lower gear ratio would be better suited for daily driving? I am thinking of using one of the Subaru diff's but I don't know what is going work the best with the rb25det transmission. I guess it would help if I knew what my current diff ratio was. Unfortunately I think it was swamped out by the guy who owned the car before me. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 23, 2014 Share Posted May 23, 2014 I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.Lecture on "Electrical Units of Measurement" (3 May 1883), published in Popular Lectures Vol. I, p. 73 William Thomson (June 26, 1824–December 17, 1907), 1st Baron Kelvin, often referred to simply as Lord Kelvin, was a Scottish physicist. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.