Rear Differential Question

[Tampa G35 Sedan 6MT]

Ok went on a 3hr drive and got about 30mpg going 70-85!

I read 2900 rpms for 80mph I was at 3200 for the same speed! Next time I buy tires I will go with a 255 40 19 and that will really give me better MPG!

I don't even feel any difference!

if your in 6th at 60 and you step on it... it used to go better but when your going 80 and you step on it... I would have to say that it is very little different!

Put it this way: if our wives were driving the car before and after they would never know anything changed

To be honest it feels faster.... If your racing it is not faster... But all the gears are more useable! when your shifting between 2700-and 3500 it makes the car much quicker because it does make enough power to move it in the first 4 gears at low RPM's

I just shift like this now when i am getting on the express way

1st 0-15 mph2nd 15-303rd 30-454th 45-605th 60- what ever speed i need to travel6th -TOP GEAR lol... Just use it to cruise!

And I never use

2nd below 203rd below 304th below 405th below 456th below 50

In 6th Gear @ 60mph I pull 2100 rpms and before it was about 2300 rpms. @ 70 2500 was 2800 and @ 80 im at 2900 was @ 3200.

3200 rpms at 90mph and 3500 rpms at 100mph...

So now "theoretically speaking" I can go 100mph when before i was going 85 and i can go 80 where i was approx going 70!

But now i have no cruse control above speeds of 60! WTF

What do i have to do to get the CC to work? I gotta have that!

Is there a relearn trick that I can use to fix this?

Thanks again!

DJ

[joe603]

That's odd...did CC work at high speeds before?

[Tampa G35 Sedan 6MT]

Yes... It only works at 60 mph and below...

I gotta get this fixed! I use the CC every day for atleast 40 mins of my drive!

DJ

[tollboothwilley]

When I went from 3.3 FD to the 3.5 my CC no longer works above 85 MPH. If I travel faster than 85 at any point it will disable my CC from working at all for a period of time. I haven't tested how long that time is.

For you, its probably the same. Don't go faster than 84 MPH and see if the CC will work. It should, without problem.

I'm very surprised that you have any issues at all though, frankly. Most people from 2004.5+ have no issues with different gears, including the 3.3.

Consider also that one of your sensors could be at fault. What year did the diff come out of?

[Tampa G35 Sedan 6MT]

It came out of an 05 350z...

Should i change the sensors

The CC works at 60mph if i go above that it just unsets itself... i can then re-set it at any speed under 60 and it will work until you go down a hill when it would back off the gas it then unsets itself again!

It will allow me to set it at any speed but only for like 1 sec then cuts off...

DJ

[tollboothwilley]

well, if those sensors weren't reading correctly I think you would have a problem with your Electronic Brake Limiting slip. It would probably trip a light. BUT...its pretty easy to swap them. Take them off your stock differential and just swap them and see if that makes a difference.

I've never heard of a 6MT having issues with changing differentials.

[Tampa G35 Sedan 6MT]

Ok still haven't changed the sensors...

but It does allow me to go up to 91 mph in 5th gear and it holds like normal!



DJ

[Tampa G35 Sedan 6MT]

changed them out...

Still the same thing...

Whats next John? Lol

DJ

[Tampa G35 Sedan 6MT]

Do you think if i reset the computer it will relearn it?

See if i set the cruise it will stay set if i have my foot on the gas keeping the car moving. It will also keep the car in cruise with my foot on the gas and i can use the accelerate button on the steering wheel to push the car all the way till the 92mph limiter.

Then it stays set for about 3 seconds and cuts out....

I might take it to the dealer to see what the hell they say... Still got an extended warranty lol

DJ

[tollboothwilley]

Did you try unplugging that sensor? I'd like to know the outcome of that.

Don't tell them you swapped gears and see if they can isolate the problem.

Cruise control was working perfectly normal before the diff swap? Its seems like a CC malfunction seperate of the differential swap. Gearing shouldn't change that at all.

I know there are TONS of people that have swapped gears and I've never heard anybody have any problems if they are 6MT. besides you of course...just your luck! LOL

Let me know if you tried the sensor though.

[ex35->g35]

Was this ever figured out? I'm having the same thing.

[jmann]

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...

Why would this cause a decrease in MPG's? Technically cold air causes more fuel to be added and as a result most people get worse MPGs in the wintertime.