Gearbox jumps back to "D" … TCL pulls in all the time

[allaroundoz]

Hi,
we are a traveling family and I have just introduced us as new members here.

I will have to start a few posts as various issues on engine, drive train and electronics occur regularly.


#1 GEARBOX JUMPS FROM Manual to DRIVE
Since Kakdu NP I experience the gearbox to jump from 4th (our preferred gear for towing). Especially after long drives, hilly & winding roads or sometimes without any further notice. No mather what I do with the gear lever, I can not switch back to "manual automatic" as gearbox stays stubbornly in "D". Pulling over, restarting the engine solves the issue – but sometimes only for 3 minutes.

#2 TORQUE CONVERTER LOCKER PULLING IN/OUT
At the end of crossing Nullabor our car has developed a strange behavior. When driving in 4th gear (automatic) I experienced the revs going up by roughly 300 every 2 seconds, dropping again and going up again. As far as I have found out it the Torque Converter Locker that is pulling in and out all the time. Annoying, is there anything we can do about it?

Any idea on issue #1 as changing gears is vital for us – especially when approaching a hill as towing a van requires 3rd gear.

TIA!

***
driving a Nissan Navara D40 2010, ST (Spanish model), 4WD, automatic, Diesel
167.000 km, all services done, ex-mining car, not a rocket while towing our van

 

[Old.Tony]

We tow a 2.5T van a lot too, and I usually just leave mine in drive. There was a glitch with the STX550 gearbox programming where it would slip to auto mode from manual but that was usually only when 4LO was engaged. It is possible the glitch occurs for other reasons. There's no real reason why you can't drive (on flat ground) in top gear. When climbing hills, I manually change to a lower gear, but it's 'D' for everywhere else.

The TCC engagement depends on several factors, usually the most important ones are vehicle speed and engine load. Engine temperature does play a part and this might be where yours is struggling. After the temperature problem is solved, you might find this one fixed too.

 

[allaroundoz]

I can tell that the engine gets warmer in "D" (maybe it uses 5th gear) than driving in manual 4th, that's why I prefer manual AND I am better in charge dropping a gear when approaching a hill. But maybe it's also because all my car I ever owned where manuals rather than automatics ;-)

 

[KevinE]

Yes, the drive line will get hotter towing in D, because the torque converter will keep unlocking, generating slip, which generates heat. I think that you're wise to tow in manual mode.

There are a number of things that could be causing it to jump into D when you are in manual mode, the most likely of which are; 1) your AT fluid is too low, or needs changing (flushing), along with the filter being changed. 2) you have a switch playing up somewhere, or bad wiring, in the AT, or in the PRND/manual selector.

The 1st thing I'd do is check that all of your tyres are the exactly the same & that the tyre pressures are exactly the same. Then I'd drive it where it's safe to do so, in reverse (not towing) in 2WD for at least 50 metres.

Good luck with it!

 

[allaroundoz]

I just had the entire transmission flushed (not just a oil change) to provide good viscosity to the system. Didn't help much ;-(