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Diff Ratios and what people think.

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Posted (edited)

Hi guys I’m just wondering what ratios you guys like running and I know it’s a bit like how long is a piece of string as it depends on what your doing with it. 

For a street car in tassie where we’re not out for land speed records but for cruising the mountain roads that Tassie has to offer would you go a 3.9, 4.11 or 4.3

Also what’s a 4.3 open R200 worth?

 

Cheers,

Justin

Edited by 600Z

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I ran a 4.11 with a 260z .864 5th, now with a Rb20det box with a .833 5th I pull the same rpm at 100kph with the 4.375.

 

I’d say go for it if you don’t plan long highway drives at 100 for hours on end.

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I've settled on 3.54 but my 5th gear is a 1:1 non overdrive, plenty of acceleration but acceptable cruise. Gives me 3200rpm @ 100kmh which is enough! Any more rpm would make long distance drives a bit wearing.

 

 

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Thanks guys I think I will see if I can check what 5th gear ratio my gear boxes are, there 260Z boxes as far as I know but I have a couple so I’ll do some checking.

The 4.3 would obviously be better for acceleration just don’t want it screaming on the highway at 110km/hr.

 

Justin

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What is your tie size Justin?

I'll input it all into the gear ratio program & see what it spits out.

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Posted (edited)

Speed is in MPH.

3.9 (Rev limit set too high - should be 7000rpm)

4.11

4.375 (4.4)

ZRatio3_9.jpg

ZRatio4_1.jpg

ZRatio4_375.jpg

Edited by Lurch

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Posted (edited)

Justin, as you're running a 6.0 5.7 ltr V8 the torque would suggest a different thinking to that of a Zed with a  standard tune straight six.

If you have the t56 box like mine then 6th is 1: 0.5.

I'm running 29" dia rear tyres, for the period appearance, and the 3.46 diff offered plenty of drivability, so with even smaller tyres this would, by my reckoning, be as short as you would want to go. You'll have trouble with grip going any shorter. If you add grippier tyres you'll risk over-stressing the drivetrain.

I actually ran a 3.07 diff on my Tassie tour and was revving 1400 RPM at 110km/h, and returned 7.8lt/100km. (Gary, that's around 36 mpg in proper units.

The 3.07 is a bit hard on the clutch in 1st, particularly on hill starts, so I'll be swapping back to the 3.46.

Edited by PeterAllen

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Thanks Lachlan that’s a very cool calculation program I think I’ll stick with my original plan and use one of the 4.11’s I have it’s just that I know where there is a 4.375 diff but probably not worth worrying about as the 4.11 will certainly be an improvement over the standard 260Z ratio.

Whats the going price for a 4.375 R200 open diff?

 

Hi Peter, it’s actually not for my orange 260 with the LS, I have a 3.7 LSD in that but I do have a 3.9 LSD to go into it to try. Should make it a bit more pokey I’m thinking on our roads down here.

I am working out what diff to put into my wife’s 2+2 and I might even change the diff out in my other 260Z to pick it up a bit more after I get my finger out and fit one of my sets of Dellorto’s. The motor in that one is a L28 with flat tops and a P90 head somit would be nice to liven it up a bit.

How was your road trip down there? I was annoyed that I was away at work and didn’t get to catch up.

 

Cheers,

Justin

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Posted (edited)
9 hours ago, 600Z said:

...How was your road trip down there? I was annoyed that I was away at work and didn’t get to catch up...

Covered here Justin - Longford was a real hoot. Click on the arrow in the top right of the box below.

 

Edited by PeterAllen

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I’m glad you enjoyed your time in Tassie, looks like you struck lovely weather too. 

Justin

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I guess while this thread is here I might try to figure out which diff I've got installed... 

I have the early 240z box and when doing 110kph I'm doing off the top of my head 4,000rpm. A bit revvy for highway driving, but pretty nice and close for getting to that speed on a L24.

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Your Tacho is inaccurate Robbie.
We've already checked the diff ratio & it comes up as the standard 240Z R180 3.9

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Posted (edited)

Oh yeah right! I forgot about it reading strangely! I'll have to figure that out at some point too!

Edited by DreamZproject

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