Choosing a diff ratio

[Wally]

I'm at the point where I'm looking for a diff and I think I've decided on the 3.5 R200 from a 350z. This would also give me the benefit of having two speed sensor rings for doing traction control and other bits with the ecu.

I'm using a CD009 gearbox from a 370z. I know first gear is quite short. What's everyone's thoughts on the below graphs. 2650rpm in 6th would sit at 70mph so at motorway speeds the engine would be ok. It's the usefulness of 1st which I'm trying to guard.

Tyres will most likely be 235 16r45


Changing at 4500rpm

Changing at 3500rpm

 

[Alphabettispaghetti]

whats the max rev chart's look like? thats where you need to look to see where it drops with the engines probable power curve.

 

[Wally]

With the above charts I was looking at day to day usability.

Max revs.

 

[Alphabettispaghetti]

I think you've got it there. I'd be tempted by a higher diff if anything.

you've got 2-3-4th as fun, then really long 5th and 6th for 'cruising'?

 

[Wally]

I think you've got it there. I'd be tempted by a higher diff if anything.

you've got 2-3-4th as fun, then really long 5th and 6th for 'cruising'?

Thank you franky. Sane setup with a 3.7 for comparison.

And a 3.9

With the higher diff I'd be worried at 1st being so short it would be unusable.

 

[jonbills]

perfect for a 12.5 at Santa Pod.

 

[Wally]

perfect for a 12.5 at Santa Pod.

Well it's definitely got to go down the strip at some point [emoji1787]

 

[Alphabettispaghetti]

perfect for a 12.5 at Santa Pod.

isn't that as quick as your L series?

 

[Alphabettispaghetti]

Thank you franky. Sane setup with a 3.7 for comparison.



And a 3.9


With the higher diff I'd be worried at 1st being so short it would be unusable.

See, i'd be 3.9. it looks more fun and with your long 5th/6th you've got nothing to worry about.

 

[jonbills]

isn't that as quick as your L series?

quicker, although maybe this year...
Skiddell's L series did 12.45

 

[Wally]

I might risk it and go 3.9. 2-4 will definitely be the play gears. The car will be set up for handling and will be perfect for the track and road. 6th will be sat at 3000rpm at 70 so not horrendous.

The eBay search for a diff begins.