2006 5AT with 3.5 ratio 6MT Diff - Cruise Control OK?
 

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!

Supporting reference:

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

Supporting reference:

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

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.

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.

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

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.

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)?

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

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.:cool:

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.

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.

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.

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*

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.

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.

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?

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.

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.

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

https://cimg5.ibsrv.net/gimg/my350z....9911b62d92.jpg

:thumbup: Wow.. Now that's a Pinto I would not be ashamed to drive.. I remember doing that to the old Chevy Vega's too back in the day..

Got my 6MT vlsd pumpkin today! See picture. Set of 3.7 gears plus seal and bearing set on its way from Z1 Motorsports.

Next weekend I install the Stillen underdrive crank pulley, and after I get the gears next week the pumpkin goes to a local trans shop for a rebuild with the 3.7s.

More fun ahead!

https://cimg1.ibsrv.net/gimg/my350z....9ded01ba2f.jpg

Damn, you don't play around... Nice. Personally, I tend to stay away from 'underdriving' pulleys. As I'm sure you know, it can put positive/negative strain on accessories. I'd go with lightweight, not underdriven.

where did you end up getting it from LKQ?

How is the shop that you are going to? Are they familiar with nissan diffs? What are they charging to swap gears and fully rebuild it?

Yes, got it from LKQ for $165 plus shipping, from a 2006 6MT Enthusiast model totalled in a front-end collision. Looks to be in pretty good shape with no visible leaks, but I'm getting it rebuilt anyway.

There is a small shop right on the way to work for me in East Hanover, NJ, called Morris County Transmissions. They only do trannys and differentials. I sent them an email but haven't talked to them yet. Once I get a quote I'll let you know.

By the way, I also purchased the Z1 polyurethane bushing set and bushing tool. I figure since I'll have the diff out why not replace the failure-prone fluid-filled bushing too.

The gears, bearings and seals arrived yesterday so today I drop the pumpkin off for the rebuild. Progress!

https://cimg8.ibsrv.net/gimg/my350z....4821c24ad8.jpg

What are they charging you for rebuild/swap gears?
Also, did they ask you for any additional shims? Do they have shims for the nissan diffs?

Charge will depend on how many hours it takes @ $100 per. He estimated 2-3 but one never knows until one looks.

He said he had plenty of shims.

Normally would take about 4-5hrs cause you have to put it together and then take it apart to make sure all is good on clearances. do they planing on cleaning housing before rebuild ?

need help installing it? cause i am going to be doing mine, so wanted to see how much of a pain it is to take out that subframe bushing

I didn't ask him to clean the housing - it's pretty clean and degreased already and it's going where no one will ever see it, so not a big concern for me. Maybe I'll paint it if I have extra time before the install.

Ill be doing it in a few weeks with my brother-in-law; between the two of us we should be good. The bushing will be the big headache but the special removal tool from Z1 should help in that regard. I'll try to take pictures along the way.

I'm very frustrated. I have been working on the car since yesterday pm, and I cannot get the crankshaft pulley bolt off to install the new Stillen underdrive pulley, even with a 3/4" breaker bar and 3 foot extension and a steel pulley holder tool. I bent the pulley holder tool from all the force I was using (see picture). The bolt didnt budge! So...

I put the car mostly back together and took it to the local mechanic shop. Very good shop. They said, sure we'll do the whole install for you for $130. Great, I said!!

One hour later the mechanic comes out and says he can't get the pulley bolt off either, even with his professional air tools! They didn't charge me but I'm still disappointed. Guess the new pulley goes up on ebay or the marketplace. At least I didn't break the car.

Now I'm home and I'll eat lunch, jack the car back up and finish putting things back the way they were. Still have the diff install to look forward to, though!

https://cimg6.ibsrv.net/gimg/my350z....95ed2901d3.jpgThose two pins are supposed to be straight and in line with each other!

After the underdrive pulley fiasco, I decided I needed to do something else while waiting for the gears, so today I installed a set of Works Bell carbon fiber paddle shifters. Took me pretty much all day, most of that time spent figuring out how to take apart the steering column, scuff panel, console, where to get the power and ground from, etc.

Ended up tapping into the cigarette lighter for power and drilling a chassis bracket under the dash for the ground. Put it all back together and voila, it works. Still optimizing the paddle position but combined with the Transgo Kit the fun factor is definitely high!

Should be a nice combo with the 3.7 gears. Can't wait...https://cimg4.ibsrv.net/gimg/my350z....6070417f2d.jpg

Just wanted to see if you finally got the gears installed and impressions

Still haven't gotten the diff back from the shop. Should be ready some time this week; I told him no hurry and I guess he took it to heart...
Looking at next weekend for the installation; right now I'm on my way to London for work.

Well not sure if model year matters or not, but my '03 5AT with 3.7 gear, I have no CC. I turn it on and the light just flashes.

But I wouldn't change it back at all. I love have the 3.7 gear because you really get to take advantage of the low-end torque if you have supporting mods. Just take'er easy for a couple of weeks even after break-in. It'll take some getting use to depending on how heavy your foot is, haha.

Thanks for the feedback, Waldo. It's my understanding that the CC issue only occurs in 2003-2004 Z's, with 2004 1/2 being the approximate cutoff. I guess I'll find out soon enough.

It will be tough to baby it at first but maybe just a few short bursts won't hurt...;-)

Did you swap out the LSD as well or stuck with OEM?

swapped with an '05 VLSD, gave the shop a rebuild kit with bearings and seals, and had them install the 3.7 gears.

Differential is ready. $500 for the rebuild. He said he had to pull it apart 4 or 5 times to get the shaft run-out right with shims, not a simple procedure...

I'll pick it up when I get back from the UK, then slap it in. Stay tuned.

OK, it's done!

Took us 9 hours...three of which were just getting the rear diff bushing out. I used the Z1 removal tool and the rubber part of the bushing came out pretty easily, but the steel sleeve took a long time and many, many wrench strokes in the tight space. Got it out finally, though. Replaced all three stock bushings with Z1 solid urethane bushings. I did not need to remove any of the stock exhaust or loosen the anti-sway bar to do the removal or installation; it was tight but with two people holding it and maneuvering it we managed.

I'm still in the break in phase so no stomping on it yet. But after 60 miles so far (in 2 separate trips with cool down in between) I can say cruise control still works! That is, at up to 60 mph, which is as fast as I've gone so far.

One BIG difference I've noticed is from the bushings - I love them! Since the Transgo kit installation I've noticed that sometimes shifts (especially 2-3 and 3-2) are accompanied with a thud from the rear...NOT ANYMORE. All shifts so far have felt very smooth and solid, the drivetrain feels much tighter and slop-free. I like it.

There is a very low gear whine on and off at 55-60 mph when the car is coasting, which I attribute mostly to the solid urethane bushings. Perhaps break in will reduce this, but it's not at all loud. I hear it because I'm listening for it.https://cimg6.ibsrv.net/gimg/my350z....ed819bb527.jpg
https://cimg7.ibsrv.net/gimg/my350z....1f32ba10c0.jpg


That's it so fa​​​​​​r. I've attached pics of the Z underside with the diff out and also after rear bushing removal.

Update: after 130 break-in miles, 20 or so at a time with cool-down in between, the little bit of gear whine around 50 mph is greatly diminished. It sounds maybe 5-10% louder than the stock 3.3 gears. At all other speeds below 50 it's just like stock. Completely acceptable. Whether it's the gears, the bushings or some combination of the two breaking in, who knows.

Now that I'm past 100 miles I can take it up to 65 to 70 mph. At 500 miles I'll change the gear oil and then it's fun time! Cruise control still working.

Good to hear on the progress. How are the rpm's at 50mph are they that much higher then stock?

Did you clean up your magnetic drain plug to see how much metal you will accumulate during break in?

71MPH is right at 3000 RPM. The drain plug was cleaned, so whatever is on there was from my gears. At about 280 miles now. Should be at 500 by the end of the week, then I'll change my gear oil and see what's on the plug.

Hmm...seems like I made a mistake in the installation of the new bushings. There is a black metal "tophat" washer on top of the stock front bushings that isn't mentioned in the directions. I put it back on top of the new bushings. I asked Z1 about it and Russ just told me that it should be left out, so I guess I'll pop those out when I change the diff fluid at 500 miles. Hopefully I can just pull one bolt at a time, tilt the diff a little and slide them out. Not a huge disaster.

Hey, I had a 50:50 chance with my guess...

If you don't have vibration from the driveline it's probably not an issue but try it and see if it changes anything.

I do notice a little bit of vibration some times, not a huge amount but sometimes I get a low chugging when I'm accelerating, although it is not consistent. Sounds kind of like the engine but out of sync with it. Hoping that removing the plate will eliminate that. Doing it today after work.

That was easy enough. About a 10 minute job to loosen the three diff bolts, remove the front bolts one at a time, and slide the black washers out. No problem. The intermittent minor vibrations are gone, not that they were very noticeable anyway.

Still some increased gear noise at certain speeds (45 and 65 mph, other speeds quiet as stock), but I guess that's the price for having solid poly mounts. I think I'll dynamat the trunk and then it should be pretty quiet..

Changed the gear oil today at about 575 miles. Break-in was done with Pennzoil 80W90 dino oil. Just changed it to Redline 75W90 synthetic. I must say, the Redline significantly reduced the gear noise! I'd say the rear is now just as quiet as stock except for a very slight whine around 45mph - I'm sure a little Dynamat in the trunk will take care of that. At highway speeds of 70-75mph there is no gear noise at all.

Cruise control still works fine, tested up to 75mph.

The drain plug magnet had a coating of fine black particles on it, likely the worn material from the gear teeth breaking in. No big pieces or chunks (see picture).

https://cimg2.ibsrv.net/gimg/my350z....b7f561a0af.jpg

Performance-wise I love the 3.7 gears. Acceleration feels significantly quicker than stock, and with the poly bushings and Transgo kit the shifts are fast and firm to keep me pushed back in my seat. These three mods go very well together.

Glad to hear you are enjoying your new gears. How is it when you stomp on it from 0mph? DO you get a lot of wheel spin?

My 3.9 rear diff project is put on hold until i can figure out why my oil pressure is low at idle. Cant seem to come up with an answer. Already changed the sensor and dropped pan. Engine sounds fine no ticking. Either pump decided to just randomly give up, or motor is toast after sitting for majority of last 2 yrs.
Fu$king hate idea of spending all the money to get the parts for upgrade and motor is toast.