Final drive ratios

[Bigmike40]

As I understand it the Q's could get better highway MPG if the final drive ratio was "geared" towards economy vice power. Is there a solution for this? Are there any aftermarket solutions that will be cost effective, I don't want to spend $3k for a 2 MPG advantage. Just thinking out loud.

I have owned my Q for 9 months and in mixed driving I am averaging around 15 MPG. I am making a road trip this Spring so I am interested in the highway cruising MPG.

Mike

[maxnix]

Should get at least 20 mpg on any highway, 22 at best.

If the G50 could pull redline in top gear, speed would be near 200 mph. It is geared for highway economy, hence the relatively slow accelleration from rest.
Modified by maxnix at 7:53 PM 2/22/2009

[Q45tech]

Only the 2002 Q45 had an economy rear end ratio...........the 2003-2006 got a ~~ performance ratio because so many of buyers complained about poor acceleration vs early magazine articles.

The overdrive in 5AT is not 0.694 [as 90-01 4at was] top gear is 0.834.An ideal diff gear would be 2.95 [to match the 90-96 ratio] your 2005 has a 3.133 ratio or 6.2% higher than ideal

WHEREA AS the 2002 Q45 had an ECONOMY ratio of 2.76 or 6.9% below ideal.

If you can find a 2002 junkyard wreck that year only diff will reduce engine rpm by 13% giving a ~ 10% improvement [2 mpg] highway cruise MPG.

AND a 4% or 0.6 second increase in quarter mile or 0>60 time.

2.76 vs 3.133

[Q45tech]

If you can find the 2.79 diff for ~ $500 and only get charged $500 to swap it. {ASSUMING no other ECU/TCS/ABS problem occur from swap don't know}

At $2 per gallon mixed driving the $1,000 cost could be recovered in driving 10,000 miles. At $4 gal recovery is 5,000 miles.

After all what's 0.6 second acceleration loss to those where MPG is important.

WARNING THERE WERE NOT MANY 2002 Q sold so finding one will be difficult in a junkyard and may require checking hundreds or thousands.

Those with money to burn could buy the gear set or whole diff from the dealer for $2000-$2500?

Unfortunately 90-96 don't have an easy 3.08- 3.3 option without loosing VLSD. Not sure a 19- 14 year old engine could pull a Q with a lower diff gear than 3.538...............except in very flat terrain.

[Bigmike40]

Q45TECH,

Thanks for the information, it gives me options. I think it might not be worth it since the availability of 2002 Q's is low.

Mike

[maxnix]

And who wants to delete VLSD?

[Q45tech]

If you were an expert technican/engineer I'm sure someone could design a method to attach the vlsd module internally to a housing that might fit the 2002-2005 Q45....................the deletion was just a cost cutting measure not a technical limitation.

Always keep in mind that Nissan didn't change the 3.538 to a 3.694 [4.4% increase] for the fun of it or for magazine test, but because of some problem in lugging the engine with AC on in hot weather up a minor incline.

Probably some internal rule about the number and duration of down shifts with cruise control on during test loop.

My guess is the new engineers forgot that the old VH45 produced more than rated torque and the VH41 produced a little less. After all displacement dropped 8% and they increased diff by 4.4% and dropped weight by 5% and it got heavier each year after 1997.

Same thing happen with 2002.........the final adjusted VK45 was no better than old VH45 in potential peak torque [though the torque curve was flatter] after they built the 2002 and ran it in US to be able to change diff gear in only one model year means they already had it designed and built.

They tried to slip one past to see if they could get away with it [better MPG] and got caught by magazines and public uproar about not meeting promised acceleration.

Makes you think they sent ringers to US to produce the EARLY magazine acceleration numbers then delivered econo versions to sell in 2002!

[kentuckyslider]

Back from the dead. Does the 3.13 in the 2003-2005 have 5 bolt axles? I have a 2000 model 3.69 gear in my LSx turbo S14 and I'd like to go to the 3.13 gear for the 1/4 mile.

Is it no vlsd? If not can I put a locker in it?

[kentuckyslider]

Anyone??

My question is this....

If I buy a 2003-2005 Q45 rear diff can I...

A. put a locker in that diff if it is open?
B. put the 3.13 gears from that diff in my 2000 Q45 3.69 diff?


any help would be appreciated.

[elwesso]

The 02-05 Q do not have a limited slip, and they use the 6 bolt flange (equally spaced). The Y33 and F50 diff are both R200s. I wonder if you could make a franken-diff with the ring and pinion gear from the F50 diff but retain the viscous coupling... Either way, I guess you could weld it.

Note that any Nissan differential that's a limited slip will have a sticker on it indicating it, and normally they refer to it as an "R200V" for the VLSD or "R200" for the standard version.

The Y33 differential is a lot closer to the 300ZX N/A Z32 differential than the 90-96 Q, in fact the Y33 diff is almost identical to the Z32 diff except for the different gearing.

[kentuckyslider]

So I need to buy a 2003-2005 F50 diff and swap the gears from it into my 3.69 Y33 diff if I want to retain my 5 bolt axles.

OR

buy the 2003-2005 F50 diff AND axles and buy a locker for it.

that is my options to get a 3.13 gear with vlsd or locker in my LSx turbo drag 240

[thehacker3]

As I understand it the Q's could get better highway MPG if the final drive ratio was "geared" towards economy vice power. Is there a solution for this? Are there any aftermarket solutions that will be cost effective, I don't want to spend $3k for a 2 MPG advantage. Just thinking out loud.

I have owned my Q for 9 months and in mixed driving I am averaging around 15 MPG. I am making a road trip this Spring so I am interested in the highway cruising MPG.

Mike

If you're only looking for highway mpg, rest assured, it'll get around 21 if you drive it normally. I average around 13-15 mpg combined, but 21+ during road trips on the highway.

[kentuckyslider]

As I understand it the Q's could get better highway MPG if the final drive ratio was "geared" towards economy vice power. Is there a solution for this? Are there any aftermarket solutions that will be cost effective, I don't want to spend $3k for a 2 MPG advantage. Just thinking out loud.

I have owned my Q for 9 months and in mixed driving I am averaging around 15 MPG. I am making a road trip this Spring so I am interested in the highway cruising MPG.

Mike

If you're only looking for highway mpg, rest assured, it'll get around 21 if you drive it normally. I average around 13-15 mpg combined, but 21+ during road trips on the highway.

Dude posted that over 4 years ago. Don't think he's headed back to check up. I was just curious how to get a 3.13 VLSD rear in my 240.

[cnichols]

Find anything out? I have a 2002 Q and want the same end result as you for it. I think I'll be fine with a 90-96 Q diff for the 240.

I'm guessing our best bet is to see about swapping it to an older style diff (Y33/J30/Z32) completely or seeing if one of the newer style diffs (G35/37/350Z) will be a direct swap or the VLSD part can just be swapped in. I was just hoping that somebody had already gone through all the trouble because I just don't have the time.