I have 2 Maximas that have topgear lockup once the tranmission warms up. I've looked in my owners manual for my '06 G35x and can't find any mention of this feature. The X's trans doesn't lockup in 5th. Is this the way it is or do I have a problem.
Also, in another thread the road speed vs. engine speed calculated to almost 27mph per 1k rpm, same as my '05 Max. My G35X is going 25mph per 1k rpm with stock 215/55-17's. Anyone see the same thing?

 

I see the same MPH. ~80MPH i'm approx 3000-3100RPM on the tach.

As for 5th gear lockup, i'll check on my ride home today how it behaves. I beleive it locks up, but not completely. Not like a manual trans really. Even in tiptronic mode i don't beleive the converter is fully locked. I'll reply later after my commute home

 

The JATCO 5AT can/will lock in 3rd, 4th, and 5th. If your tranny wasn't doing this, it would throw a code related to lock-up clutch/unit. The 5AT is very responsive, the gearing is deep, and the TC has a higher stall therefore the TC lockup isn't nearly as obvious. The lock-up mechanism is quick to release and is quite smooth.

As for the engine vs road speed, there are simply too many factors like overall tire height plus are you factoring in that the G35X has a deeper final drive than the standard RWD G automatic (3.3 vs 3.5)?

 

3100 RPM at 80MPH on my '06X with stock 215/55's.


As for locking in 5th, it does. It's just not tight like a manual. If i stab the gas it blips up maybe 100RPM. If i let off, it drops maybe 100RPM.

At lower speeds, it drops to idle though, as soon as i give it gas, it blips up to around 2000RPM or so and then locks up again

 

Sorry to disagree with you DaveB. There are NOT too many variables. The internal trans ratio is known. The final drive ratio is known. The solling circumfrance of a known tire size is known. I think it was Mustang5L5 that posted an XL spread sheet that calculated the road speed in each gear and engine speed. I have it saved on the computer at work otherwise I'd post it again. If it wasn't you Mustang I can't remember who it was and I can't find it now.

I'm pretty sure that the engine speed drops to about 1k on the highway when I take my foot off the gas. I will double check and report back.

In 5th 2.0Krpm= 50mph, 3.0rpm=75mph 3.2K=80 in my car.

 

The coupling is so loose I would hardly call it "lock up." If I tap the throttle at 80mph I will see 500-600rpm rise before the speedometer moves. 2004 G35x.

 

Variables I was alluding to were tire size which means not all 215/55R17s are the same height plus you've got to factor in tire wear. Overall, you could be talking about a difference of nearly 1" because a new "tall" 215/55R17 and a worn out "short" 215/55R17. Then there's throttle position when recording road speed vs rpm. Are you at a steady speed with the torque converter locked or are you accelerating with the TC unlocked?


Engine speed won't drop to 1K when letting off the throttle on the highway. Assuming you're not accelerating when you let off the gas, the rpms will remain the same as the engine braking feature of the auto is engaged. Not until you're at much slower speeds (I believe below 20mph), will you see the rpms fall to near 1K if you're in a tall gear as the tranny starts to downshift and the engine braking feature disengages to keep the motor from stalling.

 

At 80 MPH i'm right at 2875 RPMs. 2003 5AT.

 

No it wasn't me who posted it. Someone posted it for me when i was asking about final drive ratios for the X and RWD.

 

Here's the table again with the values for an '06 X.

SPEED vs RPM CALCULATOR

User entries here: (stock)
Tire width (mm): 215 215
Aspect ratio (%): 55 55
Wheel diam (in): 17 17
Axle ratio: 3.538 3.538
5th gear ratio: 0.834 0.834
4th gear ratio: 1 1
3rd gear ratio: 1.471 1.471
2nd gear ratio: 2.264 2.264
1st gear ratio: 3.54 3.54


Results:
Tire diameter (in): 26.3 26.3
Tire circum (in): 82.7 82.7
Tire revs/mile: 766.5 766.5
MPH/kRPM: 26.5 26.5

RPM: 5th 4th 3rd 2nd 1st
0 0.0 0.0 0.0 0.0 0.0
1000 26.5 22.1 15.0 9.8 6.2
2000 53.1 44.2 30.1 19.5 12.5
3000 79.6 66.4 45.1 29.3 18.7
4000 106.1 88.5 60.2 39.1 25.0
5000 132.6 110.6 75.2 48.9 31.2
6000 159.2 132.7 90.2 58.6 37.5
7000 185.7 154.9 105.3 68.4 43.7

Speedometer error if not corrected:
(- means reads low) 0.0%

I couldn't figure out how to post the actual spread sheet which allowed you to change tire size.

 

https://g35driver.com/forums/4479727-post36.html

 

Thanks for reposting the link Dan.