Rear Differential Question

[Tampa G35 Sedan 6MT]

I just moved about a week ago and now I have quite a drive to tampa everyday... a little over an hour.

As you guys know I love my G but I have been trying to be very conservitive with the gas trying to see what I could get best on the highway... well at 70 i can get almost 28mpg! But the problem is that I drive about 75-85 as everyone else does and that puts me around 22mpg...

If I could get the revs to be about 25-2700 at 80-85mph i would get much better gas mileage! (this is part why the new g37's 7at gets good mileage!)

So i have started to look for lower gears for the G

Problem is that I don't know what gears my diff brings... is it a 3.5? I have found 3.3's which i think will do the trick!

I am not sure what cars to look to get the lower gear from... anyone know this info?

Also i don't want to lose the LSD... is there anyway i would be able to keep this...

Much info needed Guys!

DJ

[Poyzinous]

Your 6mt has the 3.69 diff. I don't think the 3.54 from the Z is Limited slip, but if it is, that would be the ideal swap. I dont know if you could work the 3.36 gear from a 7AT model. But you'll hurt your acceleration unless you add in another 25hp.

[Tampa G35 Sedan 6MT]

Don't the Auto G35's from 2003-2006 have a 3.3... ratio...?

Are you sure i have a 3.69? i thought it was a 3.5 something...

DJ

[Tampa G35 Sedan 6MT]

Ok So I did some more research and I do think i have the 3.69.... Now is there anyway that I could use a 3.54 or a 3.3 ratio from another G35 or 350z that is open dif and install the VLSD?

I found a really good website that had imputed all the gear ratios from the 6mt... and it was about 1mph on or off of what my g does... so i think that would be really close to being correct.

To be honest with you... MPG's are really important to me now! But I don't want to think about driving a 4-banger!

the 3.3 diff with VLSD would be what I am looking for

at 3000 rpms it would be at about 86 mph and that is where my 78 is now...

I know i would loose a few pony's but I need this car as a commuter car for now!

What are your thoughs... Should I just buy an entire diff and use it open or should i purchase just the gears?...

Thanks Guys

DJ

[gwoods]

Just buy taller tires

[Tampa G35 Sedan 6MT]

I just got new tires.... LOL...

Have done some more reading and noticed that you can use (what has been posted) the VLSD of mine with the gears from a 3.3 diff...

Is this true?

DJ

[gwoods]

I suggest buy a used diff and swap that out.

It would be faster and cheaper then swapping gears and you can go back to your 3.69 later if you want too

[Tampa G35 Sedan 6MT]

Yes That is what I think i am gonna do... What about the VLSD?

Will I notice a difference?

DJ

[gwoods]

I don't know,

I'm not sure what my sedan has but it always puts down two strips of black marks and it makes me smile

[Focusedintntions]

If you're really worried about gas mileage don't drive the G...spend $1000 bucks and get a 88-92 vw gti 8v...fun lil car that's very reliable and gets 40 mpg of regular..

[Tampa G35 Sedan 6MT]

See I don't need an extra car to insure and tag.... My tag for my g this year was 85 dollars... and each jeep was 95 dollars and the wagoneer was 105 and so was the caddy!

I have 3 jeeps a cadillac and my G... I don't want another car... LOL

I will bet i can get on the upwards of 28mpg at 80mph with 3.3 gears...

Plus I hate VW's lol

DJ

[Tampa G35 Sedan 6MT]

Jeff.. You got the LSD if not you would only get 1line

[gwoods]

See I don't need an extra car to insure and tag.... My tag for my g this year was 85 dollars... and each jeep was 95 dollars and the wagoneer was 105 and so was the caddy!

I have 3 jeeps a cadillac and my G... I don't want another car... LOL

I will bet i can get on the upwards of 28mpg at 80mph with 3.3 gears...

Plus I hate VW's lol

DJ

Sell a car and buy something with 2 wheels a helmet and a suit.

Problem solved close the thread

[cjs37xs]

I get 50+ on my Yamaha in the summer. For you...in Tampa, I'll bet the sun is a little warmer for you this time of year than it is for me. I ride whenever I can (unless I HAVE to golf or some other made up reason to drive my G) in the warmer weather part of the year. I love my G, but I absolutely adore my Yammie! For the extra mpg, an added tag/insurance cost is absorbed.

Switch out the diff, and get it over with.

Not sure I'd be comfortable buying a bike down there that is 5-7 years old...affordable. Then, you'd just be a grumpy bike mechanic b/c of some previous owner's lack of care.

[Tampa G35 Sedan 6MT]

Bike is deff out...

I might just go with an open diff... but I really would like to see if I can use the LSD from My diff... I really don't want to be swapping back and forth!

DJ

[gwoods]

swapping gears or carriers is not going to be something you can do yourself.

[Tampa G35 Sedan 6MT]

I think i can get one for about 100 bux...

This is something i can swap myself right...

Just unbolt the axle shafts and the drive shaft and the 3 bolts that hold the diff up in place...

I don't think you even have to brake down the suspension or the brakes and tires.... This is great will only take a few hours!

DJ

[Tampa G35 Sedan 6MT]

If the Diff came out of a 2004 auto coupe... does that have a open diff and a 3.3 ratio?

[Tampa G35 Sedan 6MT]

Ok I have someone that has a 2005 G35 coupe 5at... He says its a 3.3 diff with LSD...

I know they make them since the canada spec 03 sedan's have a 3.3 vlsd... i guess because of the snow?

DJ

[smockers83]

Cruising at 80 I can get 26-28 MPG. It's possible.

[Tampa G35 Sedan 6MT]

Yes if your going down hill with the motor off.... LOL...

The G's get about 24-25mpg tops at 75mph... and maybe 26 at 70... No way will u get 26-28 going 80...

The revs are just too high... like 3400 rpms.. for your coupe right? (You have an auto right?)

Im at 3100 for 80 MPH with Sedan....

[smockers83]

Right at 80 tends to result in just under 3200 RPMs. I've accomplished this on more than one occasion.

[Tampa G35 Sedan 6MT]

Yes but also remember that i am in tampa... and the hot weather really hurts the mpg's in the summer too...

That could be the difference...

[tollboothwilley]

all 6MT have a 3.53 FD gearing, not a 3.69. 3.69 FD gearing was introduced in 2007 Sedans like GWOODS.

G35X have 3.53 FD as well, but it has a different flange on the differential I believe.

5AT RWD models between 03-06 were 3.35 FD.

In my 5AT I had a stock 3.35 FD and at 80 MPH I was sitting at 2875 rpms. I swapped to the 3.53 FD and my rpms went up 200 to 3075 rpms.

Previously I was getting about 27-28 MPG on the freeway cruising between 75 and 85 MPH the whole time...up and down mountainous terrain back and forth between SLC and Phoenix.

6MT have shorter gearing between 1-5 gears, but 6th gear is taller. Combined with a 3.3 FD your rpms should be around 2800.

[Tampa G35 Sedan 6MT]

John thanks for all your help...

I found a 3.35 diff from a 05 350z with lsd for 170.00 local!

Im going to pick it up this afternoon!

Should have it in by this evening =)

How much time should i allow for this install?

DJ

[gwoods]

I think its a 3 hour job.

You are going to need an alignment too after you swap it.

I think swapping the entire rear axle is easy. Setting up gears inside the axle is very difficult to do.

I paid a shop $600 to swap my 3.55 gears in my Hemi ram for 3.92 gear and a trac-loc limited slip. The reason for 3.92 vs 4.10 or 4.56 is in the hemi ram 4th and 5th are overdrive gears and with a 28" tall tire and 3.92 you are just finishing up 3rd gear in the 1/4 mile. If I had 4.10 or 4.56 I would need 4th gear to finish the 1/4

[tollboothwilley]

I think its a 3 hour job.

I paid a shop $600 to swap my 3.55 gears in my Hemi ram for 3.92 gear and a trac-loc limited slip. The reason for 3.92 vs 4.10 or 4.56 is in the hemi ram 4th and 5th are overdrive gears and with a 28" tall tire and 3.92 you are just finishing up 3rd gear in the 1/4 mile. If I had 4.10 or 4.56 I would need 4th gear to finish the 1/4

Or you could have just raised your rev-limit a little to compensate for the faster revving

DJ - It took me about 2 1/2 hours. I'd expect 2.5-3 hrs is pretty normal assuming you are using jack stands like I did.

Loosen all the half shaft bolts first, then the drive shaft bolts. The 3 mounting bolts are easy to deal with.

Dont forget to take off the rear sway bar bushing/mount bolts.

GL, put up a review.

BTW, $170 is a killer deal for what you got. I sold my open 3.3 FD diff for $200 + shipping.

Make sure you have new fluid to do that at the same time.

[gwoods]

I did raise my rev limiter from 5600 rpm to 6300 rpm.

That is a smoking deal almost as good as my $100 transmission.

I have my eye balls out for a Dana 30 front axle out of 1990 ish Wrangler. I want 3.73 or 4.10 gears. Oh and I want to pay less then $100

[Tampa G35 Sedan 6MT]

It was even better because it wasn't a u-pull-it place and they had it ready!

Cost 186 with tax and 10 bux in fuel!

Took 2 hours...

I put in Royal Purple 80w -90 gear oil!

Helped that i had an impact gun!

Thanks for everyones help!

You guys rock...

DJ

[gwoods]

Can you feel a difference? If you can pull 6th gear a side effect will be increased top speed?