Mags

OK, so I've been doing a lot of reading on this subject and I think the consensus from this forum, the G35 forum and other places is that you WILL maintain your cruise control below 85 mph if you swap a 3.5 ratio diff from a 6MT 350Z into your 5AT 350Z. If you go to 3.7 ratio or higher, though, you most likely will lose your cruise control.

There also seems to be evidence that AT made after October 2004 are able to keep cruise control even with a 3.7 ratio but there seem to be exceptions to this rule. Therefore the only "cruise control safe" swap is to the 3.5 ratio, and you need to keep your speed below 85mph.

Now I'm asking for the experiences of the members of this forum to verify what I've read. Are my conclusions above correct? Please share your first-hand experiences!

Mags

Supporting reference:

https://g35driver.com/forums/drivetrain/328080-my-review-3-5-vlsd-swap-into-5at.html

Mags

Supporting reference:

https://g35driver.com/forums/drivetr...-into-5at.html

Swaglife81

Sounds like your decision is already made up. Are you wanting people to tell you to go ahead and make the 3.3 to 3.5 swap.

Personally if it was me, I would go ahead and do the 3.69 for noticeable improvement. I haven't switched diffs in a G/Z but I have owned many cars where I ran as weak as 2.73 and as strong as a 4.56. My 5 speed mustang which is geared almost identical to the 5at is my only really close comparison. First and second gear are short and 3rs and 4th are long. 5 being overdrive and 4th gear in both is a 1:1 ratio. I can tell you when I drove factory 3.27 to a 3.55 I could barely tell a difference at all in how the car accelerated. It was minute. I think my 60 foot times went from 1.90 to 1.85 on drag radials. When I went 3.73 in that same car I took a .10 tenth of the 60 foot times going to a 1.75 60 ft time. 1.65 to 1.60 with 4.10 and small MTs just to give you acceleration. Differences.

If your rear end is trashed and you have a 3.55 than throw it in and have your cruise. If you want a noticeable street improvement you can actually feel I would definitely go with a 3.69 diff from a 6mt car G/Z. I was under the impression cruise still works on 3.69 diffs on 03-06 cars and some of the factory is people's tire sizes a 26 inch tire vs a 27 inch tire.

Mags

Thanks for the reply! No, my mind is not made up and no my stock rear is definitely not trashed. The car, although a 2006, has only 32,000 easy wife-driven miles on it. Now that it's mine its getting a bit more of a workout. Just looking for any little boost in performance I can get. Already did the Transgo kit and plenum spacer and a Stillen underdrive crank pulley is on its way to me now.

I'd love to go with 3.7s but I'd definitely like to keep CC as I do a lot of highway driving.

Anyone who has done the 3.7 swap care to comment? Even better if it was on a 2006 5AT model.

06platinumG

iTrader: (1)

I have an 06 G35 AT and 3.7 and have had no issues with CC.

Mags

Wow, great news! That makes me feel a lot better about potentially going to 3.7s!


The fact that you have an '06 AT just like mine is very reassuring.


Thanks! Exactly the info I was looking for.

Mags

Quick question: When you swapped in the manual diff to do this, did it just bolt in to the driveshaft and wheel stubs or do the flanges need to be swapped from the auto diff (driveshaft flange, wheel stub flange)?

myGspot

iTrader: (1)

Well depending on when you actually pull the trigger for the 3.7 or 3.5, I am going to a 3.9 in next few months. Had my gears and diff sitting on my floor for 2 yrs now and finally going to do it. I'll update this if you still didnt decide

Mags

Cool. It will be great to hear back how it goes. When I pull the trigger depends on a few things, including how long it takes me to find a good 6MT differential that I can use as-is or convert to 3.7s.

06platinumG

iTrader: (1)

I didn't swap the diff, I just rebuilt the one in the car. It's been so long I don't remember all the parts I swapped to make it work and the vendor that sold all parts as a package is no longer around.

myGspot

iTrader: (1)

Why not buy used pumpkin and have it rebuilt. Much safer way to go and you know its brand new pretty much.

My biggest issue with the swap is actually finding a place to do it as i also need to swap in whiteline diff bushing. I want to do it myself but no place where i can jack up the car.

Mags

I'm looking for the used manual vlsd pumpkin now. I have an ad in the marketplace here and I've submitted a request via the Partsfinder on the Slidegood web site. Once I get one I'll have the 3.7 gears put in.

I have a lift I can us​​​​​​e, so that's not an issue.

myGspot

iTrader: (1)

You can order it from LQK and probably get a 6 month warranty on it.

Care to share your lift goodness to *cough*a man in need *cough*

Mags

LKQ has a manual assembly with vlsd but they want $280 to ship it to my house in NJ from Georgia...is that typical?


The lift is my brother-in-law's, and he currently has a Pinto wagon on it getting a 302 crate V8. Once he's done with that I can get some time on it but I have no idea when that will be.

myGspot

iTrader: (1)

Yes for the most part, LKQ will ship stuff from other locations as local places might not have it. When i bought my 5AT from them it was shipped from mass. Good thing about them is that they give you a warranty and you can buy extended just in case.

Mags

OK, so I bought the diff assembly from LKQ - thanks for the tip!


I see that Z1 Motorsports has the 3.7 gear set - any other readily available sources for that?

myGspot

iTrader: (1)

I got my 3.9 set along with a full diff rebuilt kit from Z1. Also got Quaife lsd. At this point its just a matte of getting everything installed and rebuilt.

Z1 can do rebuild for you if you send them your diff out. I saw few people on the forums did that with good results. I dont want to spend the extra money and time shipping it out so i found a local place in NY that said they can do the rebuild.

I dont know if you have a place that you are going to take it but being in NYC i had a hard time finding a shop that was willing to take on the job.

Mags

There are a few little transmission shops close by who would do the work for me. I had one of them do a Quaife on a Neon RT 5-speed I built a while back. Quaife is a little more than I want to spend on this car, though.


Install on the car would be on my own - that's the fun of it all! I'd do the rebuild, too but I hear it's a bit tricky for a DIYer.

Atreyu'z 350

Whaaat.. Holy hell.. The good ole' dayz..