During a recent interstate vacation I did the following.When I reached freeway speed in "D" I shifted to manual and then shiftedup to "5". The revs dropped by about 500 rpms. If I then shifted back to "D" the engine stayed in 5. If, however , I shifted back to "M" from"D" the engine automatically went into 4th.So that is my overdrive. It can be used at any appropraite speed.Comments?

tromnai wrote:During a recent interstate vacation I did the following.When I reached freeway speed in "D" I shifted to manual and then shiftedup to "5". The revs dropped by about 500 rpms. If I then shifted back to "D" the engine stayed in 5. If, however , I shifted back to "M" from"D" the engine automatically went into 4th.So that is my overdrive. It can be used at any appropraite speed.Comments?

Welcome to NICO!

I am not sure which model M35/45 you are referring to. So, I will answer the question from my experience on my 2003 M45.

Yes, moving from D to M takes the car into 4th gear as a start. I think the software programmer's assumption was that you wanted more responsiveness in M, rather than lugging the engine at lower speeds. As well as the ability to move up and down yourself.

When I am driving around town, or going up long hills, I drive in 4th to prevent excessive shifting. Only when I get onto the highway, do I put it into 5th manually or back into D.

Also, as I recall, when using the M modes, the shifts points programmed in (remember that the selection is not the actual operating gear, merely the maximum it will shift into) the transmission is more aggressive than when the car is in D.

Hope that clarifies (assuming I understood your comments correctly.)

Note that some of the recent loaner G35's I have driven had a different Manual programming approach, where the car would actually drop the selection as it slowed. Making it closer to a true manual than the way it operates in my M, where it simply sets the maximum gear it will shift up and down to. I have an old thread about this somewhere ...

Z

Thanks for the repy.I am driving the 06 M35x.The reason for posting was that shifting into manual from"D" and then to 5th gear reduces the rpm's and therefore the mileage per gallon.I am assuming that it is the same as "D" shifting into overdrive.

tromnai wrote:Thanks for the repy.I am driving the 06 M35x.The reason for posting was that shifting into manual from"D" and then to 5th gear reduces the rpm's and therefore the mileage per gallon.I am assuming that it is the same as "D" shifting into overdrive.

Yes, it should be. The normal 5th gear overdrive in D should be the same gear as 5th in M for sure.

If you are on the highway in D, at a steady speed, note your rpm's and then when you shift to M and then up to 5th, the rpm's should be at the same value.

Z

"If you are on the highway in D, at a steady speed, note your rpm's and then when you shift to M and then up to 5th, the rpm's should be at the same value."

That is the point I am trying to make. When I shift to M and then up to 5th the rpm's -DROP-.At freeway speeds the DROP is about 400rpm's.Therefore the 35Mx does have an overdrive. You just have to get to it via manual.

tromnai wrote:"If you are on the highway in D, at a steady speed, note your rpm's and then when you shift to M and then up to 5th, the rpm's should be at the same value."

That is the point I am trying to make. When I shift to M and then up to 5th the rpm's -DROP-.At freeway speeds the DROP is about 400rpm's.Therefore the 35Mx does have an overdrive. You just have to get to it via manual.

Ah! Okay. Now I understand what you are saying (pardon my denseness), and that is weird! If I might summarize, in essence, the only way you seem to get to the lowest rpm's at a steady, constant highway speed is via 5th in M and not while in D.

Whereas, in my 2003 M45, when crusing steadily on the highway (so, the car is presumably in overdrive automatically), the rpm's in D are exactly the same as when I put it into 5th in M.

Anyone else see the same thing as me? Or is the new 2006 M (or at least the M35x) behaving differently? Like for tromnai?

I wonder if there is some TCU programming situation in the new M (or the new M35x) that requires this. Or perhaps it is a bug in the TCU. I would also ask the dealer to check it out, tromnai.

Let's hope we get other answers to this question from some other folks here. If this is a common occurrence, it might be worth taking it up with Infiniti Corporate.

Z

"Ah! Okay. Now I understand what you are saying (pardon my denseness), and that is weird! If I might summarize, in essence, the only way you seem to get to the lowest rpm's at a steady, constant highway speed is via 5th in M and not while in D."

szhosian, exactly. No pardon nescessary, a poor explanation at the start.I will talk to my dealer. "TCU"?I hope other M35x owners will comment on this thread.

tromnai wrote:"TCU"?

Transmission Control Unit. The computer inside the transmission that sets all the shift points, etc. Very closely linked (and communicates with) the ECU or Engine Control Unit.

tromnai wrote:I hope other M35x owners will comment on this thread.

Yes, please, other folks! Please try this out and comment.

Z

The purpose of the original 4 speed AT [around 1980] was to introduce overdrive. Definition of which is a less than 1:1 gear ratio.

Many modern 6, 7, and 8 [LS460] gear automatics have two [or 3] overdrive ratios.

It was easy when the speed limit was 55 mph, now with routine cruise at 80 mph you need 2 overdrive gears to optmize cruise rpm/mpg to suit different drivers/state locations.

I remember a few years ago when the 5AT came out how many people didn't read owners manual and drove on highway in 4th with the resulting 20% lower fuel mileage.

I have an '06 m45. I will try it tomorrow and report back.

BJB wrote:I have an '06 m45. I will try it tomorrow and report back.

That will be great! Thanks!

Z

OK. Just took a trip down the interstate and tested this. I set the cruise at 80mph in auto mode. The RPMs were right at 3k. I then shifted into manual which put me in 4th gear and the RPMs obviously went up...around 3.8k. Once I manually shifted into 5th gear, the RPMs were actually the same as in auto mode. I tried it at 60mph, at 100mph all with and without the cruise on.

I think O/D is the same in auto and manual.

Your thoughts?

BJB wrote:OK. Just took a trip down the interstate and tested this. I set the cruise at 80mph in auto mode. The RPMs were right at 3k. I then shifted into manual which put me in 4th gear and the RPMs obviously went up...around 3.8k. Once I manually shifted into 5th gear, the RPMs were actually the same as in auto mode. I tried it at 60mph, at 100mph all with and without the cruise on.

And when you shifted the lever back to "D", the rpm's stayed the same without budging or blipping at all, right? If so, all of the above is exactly what happens to me in my 2003 M45 too!

So ... the question is then: why is it different in tromnai's car? Weird!

Thanks for checking it out in your vehicle!

Z

Right. Same RPMs in Manual 5 and auto O/D. Maybe we are just misunderstanding what our fellow Mster is saying.

BJB wrote:Right. Same RPMs in Manual 5 and auto O/D. Maybe we are just misunderstanding what our fellow Mster is saying.

Possibly!

Or else his car is indeed behaving very differently from what we would all expect.

Or his M35x AWD model is different in some way.

Z

Yeah Interesting.

OK. Enough about transmissions. I am having the K40 radar and laser difusser installed this weekend. From all of the research that I have done, it is an awesome detector. The really cool thing is that the components are connected via bluetooth so there are very few wires to run. It will be easy to remove at the end of my lease. Additionally, it is virtually undetectable and no cabin clutter, nothing hanging from the windshield. Just two small LEDs to let you know when you are being hit with radar or laser.