D40 Diffs ratios.

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I'm looking at the system right now. There are two separate components that make the changes, activated by a single component. A planetary gear at the front of the transfer case makes the change from high to low range and vice versa, and a sleeve that slides under the chain sprocket mid-way along the transfer case engages 4WD.

I don't see a way of engaging the planetary gear without the sleeve moving. Certainly not electrically. There are switches but they're detection switches, not options we can choose.

A means of disengaging the front drive shaft would probably be easier to make. A splined sleeve that takes a splined shaft - withdraw the shaft, the shaft doesn't turn, engage 4LO in the cabin and you're in 2LO. I wonder what that sort of exercise would cost?
 
Old.Tony said:
I'm looking at the system right now. There are two separate components that make the changes, activated by a single component. A planetary gear at the front of the transfer case makes the change from high to low range and vice versa, and a sleeve that slides under the chain sprocket mid-way along the transfer case engages 4WD.

I don't see a way of engaging the planetary gear without the sleeve moving. Certainly not electrically. There are switches but they're detection switches, not options we can choose.

A means of disengaging the front drive shaft would probably be easier to make. A splined sleeve that takes a splined shaft - withdraw the shaft, the shaft doesn't turn, engage 4LO in the cabin and you're in 2LO. I wonder what that sort of exercise would cost?
Click to expand...

Sounds, Good wonder who we could get to do it. Sounds a little more then a back yard job.
 
At the very least it would require cutting the front drive shaft, perhaps bolting the new mechanism onto the front side of the transfer case would be best. This will change the angle of the front drive shaft, which may have to be catered for (especially if a Calmini kit is involved).

A reasonable machine shop ought to be able to manage it. Should be able to do it electrically too, like the e-locker - this would be an e-unlocker.
 
Man that sounds painful and costly.
Might just live with it...... Figgered the D40 would be that good in Nissan eyes that changing minor things would be head ace. LOL
I might just add gas and be done with it.
 
If you aren't needing 4WD, removing the front drive shaft will do the job.

Fit some D22 hubs to get manual hub locks (D22s can do 2LO by forgetting to engage the front hubs).

There are solutions, they just cost too bleedin' much.
 
Yeah, I use 4wd. All that sounds like a costly pain in the ass that all the d40 senors would start jumping up and down about. LOL But you may have something for someone if a little more money/time then me to test out
 
Old.Tony, i am curious as to what you think a auto NAV cruise speed would be with the 4.1 diff gears on 33's and 35's. TIA
 
D40 Tourer said:
Old.Tony, i am curious as to what you think a auto NAV cruise speed would be with the 4.1 diff gears on 33's and 35's. TIA
Click to expand...

If you use 285/85R16(33") tyres your cruise (@2,000rpm) should be 109km/h - and this diff brings cruise back to 99km/h.
 
Tough ask, because I don't know what the metric equivalent is (which is what I've used since we went metric back in 1976).

Assuming the 33s are 315/65R16, cruise with a 4.1:1 diff should be a tad over 90km/h (90.7)

If the 35s are 315/75R16s it should cruise at about 97km/h with that diff. On a standard diff (126kW YD25 with a 3.692:1 diff) it should cruise at 108km/h.

All speeds should be checked with a GPS, and NOT your speedo.
 
Old.Tony said:
With a 4.1:1 diff and 265/75R16 tyres (2.525m circumference) cruise speed is altered from 94km/h to 89km/h (instead of the 99km/h that those tyres would produce). This would lead to savings in fuel (less strain turning the wheels over). Not a bad thing if you're going to stay on larger tyres.

Even better - if you use 285/70R16s your cruise adjusts from 94km/h (standard 255/70R16 cruising at 2,000rpm) to 92km/h. Makes this diff PERFECT if you go the larger tyre.

If you use 285/85R16 tyres your cruise (@2,000rpm) should be 109km/h - and this diff brings cruise back to 99km/h.

I'd recommend the diffs to anyone wanting those tyres.

Note: it's important to consider the YD25 at 2,000rpm because that's the point where your (stock) engine is producing the most amount of torque (for maintaining speed) for the least amount of fuel. Any lower RPM and the torque falls away, any higher and the fuel input rises faster than the torque, making it not worthwhile.

In the V9X, that's 1700rpm.

Here's the formula if you want to whack it in a spreadsheet and do it yourself:

60 times cruise RPM times tyre circumference in metres divided by (top gear ratio times diff ratio) divided by 1000.

Tyre circumference is 3.141 times (2 times tyre width times profile divided by 100 PLUS rim size times 25.4) - then divide this result by 1,000 (convert from mm to m).

Examples:

255/70R16 has circumference of 3.141*(2*255*70/100 + 16*25.4)/1000 = 2.397m
285/85R16 has circumference of 3.141*(2*285*80/100 + 16*25.4)/1000 = 2.798m
Click to expand...

Some of us have long range tanks, extra Jerry cans , extra batteries etc,
Tony for some reason has a head the size of a navara filled with complicated knowledge, who did you buy your extra brain storage from and was it expensive?
 
It's a little engineering, a bit of math, and plugging away at spreadsheets since before Excel was released (I've worked on computers since 1979). My brain is worse than a sieve, and the most commonly used tool on my computer is Google - no joke!

That's why I have the odd tyre size mentioned - found it on Yahoo answers. That didn't explain things fully, so I'm still confused about sidewall size on a "33 inch tyre" but since the figures I came out with are close to what Tiger came out with I'm assuming I was fairly close. Seems that 33" means the entire diameter of the wheel, but without the sidewall measurement I can't tell width (from "33 inches") although I can work out circumference which is all that's needed for my formula, which uses the circumference to work out how many times the wheel has to rotate to travel one kilometre.
 
Old.Tony said:
Unfortunately going the other way - V9X diffs into YD25 - would be even worse, because the turbo wouldn't come on to cruise boost levels until 111km/h (I made a spreadsheet that works out the speed you'd travel at with a given gear ratio, diff ratio and engine speed). That's about 15km/h above its normal point and it might struggle rather badly - I'm betting its fuel consumption would be terrible!
Click to expand...

Tony,

Is there any chance you can send me a copy of this spreadsheet (email [email protected]). I am looking at replacing my tyres and want to go up a size or two, just trying to work through all the flow on effects down the driveline.

I drive a manual 2011 spain built STX D40.

Cheers,

Mick
 
Thanks Tony, the spreadsheet is just what I was after. quick question, where you obtained all the Diff and Ration values from? I have being searching for them everywhere.

Cheers

Old.Tony said:
No, won't do it. I'll do one better.

It's attached here for everyone to play with. Isn't complete, I did a bit of scratching around in it. Enjoy!
Click to expand...
 

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