G37S rear VLSD axle upgrade 3.69:1 ratio woot!

[ken in az]

Just thought I'd let y'all know I'm doing the rear axle upgrade.

Should only need the front companion flange to swap and 12 new grade 8 bolts with corresponding lock washers and nuts for the stub axles.

I was going to order the Nismo finned differential cover, but nahh I'm good.

The new ratio and limited slip should enhance my driving pleasure

I'll post how it goes when I'm finished

[nadzak]

Please take photos of the install if you can! I am very interested in this swap, too.

[ken in az]

Please take photos of the install if you can! I am very interested in this swap, too.

M35 wont gain that much since they are already a 3.54 ratio already. It'd be a small difference but you'd be gaining VLSD which would be nice.

What you need to look at is the 90-96 300zx NA(non turbo) rear axle upgrade which has the VLSD and 4.08 gear ratio. The V6 revs higher than the V8 so you'd make use of the added gearing. Only problem is the stub axle is a 5 bolt versus our 6 bolt setup so technically the diff won't bolt up. I have an idea to replace the entire pumpkin and axle shafts but I need to know what the spline count is on the outer axle shafts at the hubs for the stock M's as the 300zx's are 29 spline. We share nearly identical track width as the old 300zx so if the sline count is the same then the swap should work perfectly. the 300zx shares the same tone rings for ABS control as the newer M so no problems there.

[ken in az]

M35 wont gain that much since they are already a 3.54 ratio already. It'd be a small difference but you'd be gaining VLSD which would be nice.

What you need to look at is the 90-96 300zx NA(non turbo) rear axle upgrade which has the VLSD and 4.08 gear ratio. The V6 revs higher than the V8 so you'd make use of the added gearing. Only problem is the stub axle is a 5 bolt versus our 6 bolt setup so technically the diff won't bolt up. I have an idea to replace the entire pumpkin and axle shafts but I need to know what the spline count is on the outer axle shafts at the hubs for the stock M's as the 300zx's are 29 spline. We share nearly identical track width as the old 300zx so if the sline count is the same then the swap should work perfectly. the 300zx shares the same tone rings for ABS control as the newer M so no problems there.

Oh, and if you have the M35X then you already have the 3.69 ratio but you are still open axle and no limited slip for you.

Technically a pure bolt on affair would be to find a M35X diff and swap it. The M45 guys will need new Stub Axle bolts as they are different from the 35's to the 45's setup.

[nadzak]

Interesting...I'll talk to my guy Seb at Specialty Z - he is the Z specialist! Let you know what he says...

[ken in az]

Interesting...I'll talk to my guy Seb at Specialty Z - he is the Z specialist! Let you know what he says...

Yeah - just find out what the spline count is on a 350z or G35 - ours should share that same spline count and very possibly share it with the old 300zx - if that's the case - watch out! lol

[ken in az]

Yeah - just find out what the spline count is on a 350z or G35 - ours should share that same spline count and very possibly share it with the old 300zx - if that's the case - watch out! lol

Bad News today. The stub axle flanges that bolt to the axle shafts that go out to the wheel hub are a LOT larger on the M than on the G37S.

Doing a little research it looks like I'd need G37 or M35 axle shafts to use this differential. Some more research and I'll know for sure. Good thing I didn't pay too much for this G37S differential

[ken in az]

Well - as luck would have it the guy that sold me the differential actually has the axle shafts as well. He measured them and gave me the spline count.

the G37S has a 32 spline outer axle shaft and so does the M45 whoo hoo for me because the should now fit on my car.

He sent me the lengths and they are close to what the M45 has so I'm going to buy them and try them out.

M35 guys listen up!!!----You guys have a different outer hub and axle shaft than the M45. My guess is that it shares the same size flanges as the G37S so this diff might be a direct swap for you if you want a little more gearing and VLSD----

[ken in az]

Oh, and another thing. If the M35's have the 29 spline outers then it is very possible that the 90-96 300zx Non Turbo diff with the 4.08 ratio and VLSD would fit for your application with just the rear cover swap and buy the axle shafts! I've seen those diffs sell on ebay for $99 and the axles for $50 for both so that's a darn cheap upgrade if you ask me - that is if it's possible.

[nadzak]

I wonder what would that do when you drive 80 mph on the freeway. It will probable be close to 5 K on the tach...

[ken in az]

I wonder what would that do when you drive 80 mph on the freeway. It will probable be close to 5 K on the tach...

Stock 3.357 gears @ 80mph ~ 2840rpms3.69 gears @ 80mph ~ 31204.08 gears @ 80mph ~ 3450

Not that bad considering. I had my old 300zx and that thing would cruise right at 3000rpm @ 75mph stock so the 3.69's are well within limits

[ken in az]

Just ordered and should be delivered next week - G37S axles

[szh]

Just ordered and should be delivered next week - G37S axles

Lots of picture before, during and after the install please!

I know you will do this, but no harm in reminding.

Z

[Q45tech]

Just remember MPG at a steady speed [highway] is directly related to engine rpm.............10% higher 10% [21%] more fuel is used over the same time period.

But then what's another +10% [+21%] in fuel costs even when it reach $5 per gallon.

[ken in az]

I am averaging pretty close to 20mpg with my current setup and driving habits. Just got 21.1mpg on my last fillup

I'll be sure to post the results after the mod.

http://www.fuelly.com/driver/keninaz/m45

[mexillis]

So did you complete this yet? If so what did you have to do to finish it up?

[ken in az]

So did you complete this yet? If so what did you have to do to finish it up?

I ordered G37 Axle shafts that were delivered yesterday to my ups mailbox so I haven't had a chance to pick them up. I am crossing my fingers in hopes that the axle shaft lengths are close and or the inner flanges are compatable with eachother. I have confirmed that both share the 32 spline outers so on that presumption things should work out between the two. I am hoping that the lengthes are close enough that they will be a direct swap with no need to frankenstein the axles.

I'm taking the day off friday and then I'll have the weekend to work on the car - but for now it is just sitting on jackstands in the garage.

When the car comes down off the stands it'll have custom headers/element114 exhaust/magnaflow hi flow cats/g37S rear diff/freshly painted calipers

I have alot of work ahead of me, but I know it will be worth it.

[szh]

Good Stuff™!

Looking forward to seeing your results ...

Z

[mexillis]

Hell yeah I think you should open up a M shop GL with everything and hopefully the swap works, if it does I would def. like to do the VLSD swap too. I cant believe the M45 doesnt have it already along with the BBK doesnt make sense anyway good stuff man

[ken in az]

Hell yeah I think you should open up a M shop GL with everything and hopefully the swap works, if it does I would def. like to do the VLSD swap too. I cant believe the M45 doesnt have it already along with the BBK doesnt make sense anyway good stuff man

Haha - open an M shop....so I could make a ton of money off of myself

[saeedakobiakov]

how about y34?how hard would be to to put VLSD on 03 m 45?

[ken in az]

how about y34?how hard would be to to put VLSD on 03 m 45?

From what I have read on this forum - there was a guy who swapped a 90-96 300zx Twin Turbo rear differential that is 3.69 ratio and VLSD into his 2003 M45.

He claimed it was a direct bolt on with only a slight modification needed. When I say bolt on I am talking about the entire pumpkin swap - not just the internals.

I'll see if I can dig up the post....

[07sportm35]

Me fingers are crossed.

[ken in az]

Found it - zerothread/146904

[ken in az]

Me fingers are crossed.

I'll bring the ramps - or jack and we can look at your differential and see what it is under there.

[ken in az]

An update on the Differential install...

G37S Diff is installed - swapped the front companion flange from the olds M45 stock diff to the G37S diff (easy but requires an impact gun or a BF Breaker Bar and something to hold the diff flange while you torque it too 150ftlbs). The flange swat is necessary to mate the diff to the driveshaft. Everything else bolted up perfectly.

G37S axles were a little off as far as dimensions. When sitting on the ground it looks like they were about an inch longer on one side and less than an inch shorter on the other side. I figured the CV joint could soak up that difference easy but when I installed them the difference looked greater. This is a bit odd because the differentials are the exact same width and we share nearly identical track widths in the rear to the G37S. This tells me that one chassis has the differential mounted a little off from center. I'm leaning towards it being the G37S to aid in weight distribution but either way, they swap easily.

Just for fun I threw the G37S axles up in there anyway knowing the lengths were off and compressed the suspension. It turns out they look fine but I'm not 100% sure they would be so to be 100% I'm going to swap the inner CV's from the G37S axle on over to the M45 axle. That will be a 100% workable solution and have zero issues and I won't have to worry about a CV joint exploading on a big bump - lol.

Oh, and just for anyone who was wondering how much this has cost so far.....$199 shipped for the Diff and $199 for both axles - 14,000mi from a 2008 model car.

Only thing I'm looking at being an issue is the transmission speed sensor. It will show a different speed than the wheel speed sensors. The speedometer will still be correct because the Gauge cluster reads from both and in an fault condition - it will read from the "still working" sensor which would be the wheel speed sensors. I think I might have an issue with the cruise control. I've been reading up on the G35/350z forums that when the automatic cars do the diff change they loose their cruise control but everything else works fine. If that indeed is the case we are lucky because the trans speed sensor (VSS-AT) is a 3 wire pulse type sensor that you can throw on a calibration box to fix the difference. They are inexpensive from Dakota Digital $80 4 wire hookup. Only proplem is the sensor is "inside" the transmission menaing you'd need to drop the pan. Most people looking to do this mod could stand to change out to some fresh ATF anyway. Good thing I have 4 quarts os Matic S sitting in my garage leftover from the Transgo shift kit install.

Oh - and the headers are on there....big pain in the arse, but I'm redoing the entire exhaust system again. I was not happy with the welds on my last system - looked like chewed bubble gum in some areas and developed leaks. It took me 4hrs on saturday to figure out that when I bought my last spool of wire it was a different diameter than my last wire I used. That means I installed the wrong size tip in the MIG gun which was causing my iratic welds. Now I just need to somehow slow the feed rate down and I'll be back in business laying down some smooth, leak free welds.