When does torque converter lock up?

4

4x4 Nut

Member
Location
OH
Car
2004 FX35 AWD
Hello, A while ago I purchased a 2004 FX35 AWD w/ 245K on it that was in need of some mechanical repairs. The vehicle is in really nice clean condition for the miles. The damage was this- the front driveshaft U-joints had worn to the point the one connecting to the front differential broke free & the shaft started flopping around. It broke the transmission bell housing & a piece on the engine oil pan. I have everything repaired including some new engine parts (timing chains, rod bearings, gaskets, water pump, etc...) & all new fluids. Anyways, with all that said I have the vehicle running/ driving & other than trying to get the idle speed to calibrate proper (haven't been successful on the learning yet), it runs really nice.

My question is for you FX35 owners. How do you find the torque converter lock-up normally works? Mine shifts great all the way up into 5th gear, but the converter isn't locking. I can tell this because when cruising say 60-70 MPH, I can press the throttle slightly to accelerate & the engine RPMs will jump up a few hundred RPM immediately. With a locked converter the RPM's should rise gradually just as the vehicle speed increases. I've looked through the factory service manual I've found online, but haven't found a description of how it's supposed to shift. If anyone who understands what I'm asking & can describe how your's functions I'd appreciate the insight. Maybe it's normal, but just doesn't seem right to me. Thanks much.
 
Mine locks up around 30-35mph, but only if the engine is at full operating temperature and I've been driving at least 10 minutes. I can't tell whether the convertor lockup is related to engine temp or transmission temp, or both.
 
Thanks for the reply. I continued to drive it (have 900 miles on it now) & it may have just been that I hadn't driven it long enough yet. A day or 2 after posting this we took it for a 40 mile trip. It did start locking up after good & warmed up. It seems more to do with transmission being warmed up as the engine reaches operating temp quicker than that. Anyways, it's working, but not like you describe yours to do. Mine won't lock until cruising (probably 50-55 minimum) & then it's only when at light throttle. If I roll into the pedal to increase my speed or start going up a hill, it will kick out of lockup. Then locks back up once leveled out & a light cruising throttle position is used again. I read in the shop service manual (found online) that the lock-up specs are based on the throttle being 1/8 or less open so with that info & because it is locking I assume it's working correctly. There are specs at 1/2 throttle too, but the vehicle speed at which this happens is roughly 115 MPH..... Probably not going to happen with that scenario... LOL. All seems good now though. Thanks
 
I've paid more attention to it since this thread. It definitely appears to be related to transmission temperature. Engine can be fully warmed, but the converter will not lock up. I could be driving for a period of time, and it still will not lock up, but that time period changes with outside temp.
 
Found this on the G35 forum, but it's the same transmission. It is temperature dependent as most transmission controls are highly dependent on fluid temperature which affects fluid volume and viscosity.

"TORQUE CONVERTER CLUTCH SOLENOID VALVE

'• The torque converter clutch solenoid valve is activated, with the gear in D3, D4, D5, M3, M4 and M5 by the
TCM in response to signals sent from the vehicle speed sensor and accelerator pedal position sensor (throttle
position sensor). Torque converter clutch piston operation will then be controlled.

• Lock-up operation, however, is prohibited when A/T fluid temperature is too low.

• When the accelerator pedal is depressed (less than 1.0/8) in lock-up condition, the engine speed should not
change abruptly. If there is a big jump in engine speed, there is no lock-up.

-------------

and

-------------

Vehicle Speed at Which Lock-up Occurs/Releases

Lock-up - Closed Throttle 31-36 mph

Lock-up - Half Throttle 86-91 mph

Released - Closed Throttle 29-34 mph

Released - Half Throttle 65-70 mph

• At closed throttle, the accelerator opening is less than 1/8 condition. (Closed throttle position signal OFF)
• At half throttle, the accelerator opening is 4/8 of the full opening."
 
Yes, that is about the same info I had found in the Infiniti shop manual. Only thing that seems odd is how easy it will kick out of lockup (throttle opened more than 1/8 the way). It doesn't take much of a incline or speed increase to cause that. But, it's working according to Infiniti description so all is well. Thanks guys.

---------- Post added at 11:01 AM ---------- Previous post was at 10:54 AM ----------

I have another issue that just started over the last couple weeks. On rare occasion after I've backed out of a parking place & shift into drive it will pause in neutral & take a few seconds to actually go into gear. This has only happened when cold & only a handful of times. My fluid & filter was changed when I had things torn apart for repairs & I've put about 2000 miles on it so far. Fluid level is still ok. It shifts & functions good otherwise. Anyone else ever experience this?
 
You must log in or register to reply here.
Back
Top