Lock Up Torque Converter

placidarc · Mar 29, 2016

Hi.
I have a 2002 V6 Narvara. When travelling at about 2200 RPM in overdrive the rev counter fluctuates by about 200 RPM. It feels as though the TC keeps locking and unlocking. If I select 3rd gear for a while then go back on O/D the problem vanishes for a while then returns. It only seems to happen when there is little load on the engine, when it goes up slight hills it behaves perfectly. Rather than keep changing gears is there any way I can disable the TC when the problem occurs.
Regards.
Mike

Old.Tony · Mar 29, 2016

The TC lock function is automatic but depends on several variables (light engine load, engine at normal operating temp, gearbox in certain gears, vehicle travelling at or above specific speed).

I've never heard of a V9X (RE7R01B gearbox) having this problem. Early (2006-2009) D40s with the YD25 ( and RE5R05A) had TCC engagement issues which were caused by the clutch itself not being able to properly engage. Nissan were replacing the entire torque converter to resolve the issue. That's not to say that the problem might have been easily resolved by removing a piece of excess metal left behind after fabricating the unit or something else, but that's how they do it.

However, surging isn't uncommon on our CR diesels. Mine has done it twice now, each time fixed by adding a can of Liqui Moly Fuel System Treatment to the fuel tank. 100-200km of driving and everything was back to normal. Under moderate to high loads the surging wasn't noticeable because there's a lot more fuel and air moving through. Under light load the engine is more sensitive to small changes. Might be worth a try? The worst you could do is spend $25 to make sure the fuel system is clean!

Dion · Mar 29, 2016

I think the OP is talking about the V6 petrol, D22 with VG30, judging by the 2002 year. And being auto, I think it must be 4x2 to have that engine and an auto trans?

RE4R01A I think but I never did much with the 4x2 V6s.

Based on the dither you describe, the first thing I would replace is the AT oil temp sensor; the control logic bars TC lockup until the oil is at temp; if your temp reading is incorrect and variable from the sensor it might dither... the extra temp from running in 3rd for a while may push you into a temp range where the sensor works well enough.

100% guesswork there... YMMV

There's not a whole lot you can change externally besides that and fluid level check and fluid replacement. So start with those, and failing that, you can hardwire a TC lock switch to keep you going a while longer and save you cracking open the valve body or taking out the TC

bods · Mar 30, 2016

I'd go with the above suggestion, but if you're not sure when the fluid was last changed (if ever) I'd start with that.

placidarc · Apr 3, 2016

Dion said:
I think the OP is talking about the V6 petrol, D22 with VG30, judging by the 2002 year. And being auto, I think it must be 4x2 to have that engine and an auto trans?

RE4R01A I think but I never did much with the 4x2 V6s.

Based on the dither you describe, the first thing I would replace is the AT oil temp sensor; the control logic bars TC lockup until the oil is at temp; if your temp reading is incorrect and variable from the sensor it might dither... the extra temp from running in 3rd for a while may push you into a temp range where the sensor works well enough.

100% guesswork there... YMMV

There's not a whole lot you can change externally besides that and fluid level check and fluid replacement. So start with those, and failing that, you can hardwire a TC lock switch to keep you going a while longer and save you cracking open the valve body or taking out the TC

Hi Dion.
Thanks for your reply. Where would I find this AT oil temp sensor.
Regards.
Mike

Dion · Apr 3, 2016

I remembered it being externally accessible, but it's actually not. So, as an idea, obtain a new temp sensor, new AT fluid, a new filter plus a new sump gasket, and hit it all in one go.

Google images for helpful pictures.