Jump to content
HybridZ

Best final drive ratio for RB26 Swap


EF Ian

Recommended Posts

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?

Link to comment
Share on other sites

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. 

Link to comment
Share on other sites

^^ 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...

Link to comment
Share on other sites

  • 1 month later...

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?

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

  • 4 weeks later...
  • 1 year later...

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)

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

  • 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.

 

William Thomson (June 261824December 171907), 1st Baron Kelvin, often referred to simply as Lord Kelvin, was a Scottish physicist.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...