towing tips

[crack]

gday fellas

just chasing some tips for towing with my 2010 d40 st auto dualcab.

towed a trailer today with a weight probably in total of 2000kg. when towing i sat on about 100km and turned overdrive off when going up hills etc, and turned back on when on down hill runs and flat road. did close to 200km and used half a tank.

cheers jack

 

[Old.Tony]

I don't fiddle with the overdrive in mine (2009 D40 auto dualcab). In overdrive, the torque converter will lock if the accelerator is held under 50%, which means every revolution the engine does is directly transmitted to the rear wheels. If the thing unlocks, it returns to its "fluid drive" state.

Torque convert lockup is done by the TCC solenoid, controlled by the TCM that rests inside the bottom of the auto box, plugs are on the side with connection to the ECU to provide signals re speed, engine load, accelerator position etc.

At 75km/h or more, with throttle <50%, in overdrive, the TCM will activate the TCC and gradually lock the converter. It takes about 5-10secs for this to occur.

I really like it when it happens, because it's a direct drive. It also means I'm not pushing hard and I'm saving fuel.

The Navara seems to like about 95km/h - about 100km/h indicated on the speedo, give or take - or RPM at about 2,000, which is about where the engine's torque climbs up rapidly due to the turbo coming on strong at that point (give or take a little).

Still, we're using 17-18LPHK when towing our full van (1.8T, pics in my garage). It's a double axle, electric brakes with proportional controller - a must have with heavy tows. I'm not unhappy with that, but would like to try being even more gentle. At Christmas we're doing over 7,000km in a round trip, I hope I can improve on those figures!

 

[crack]

whats the torque converter? and TCC, TCM? what do you mean by direct drive?

sorry but im new to autos this is the first ive owned apart from the commodore buti rarely drive that. the guys at the local nissan say dont tow with O/D on, but they also thought there was child anchor points, so im a bit scepticle on their knowledge.

jack

 

[Old.Tony]

Sorry for dumping the jargon like that, I'll clear that up now.

The torque converter is the liquid clutch in an auto. It performs the same task as the clutch and pressure plate in a manual, but instead of being a solid connection, it uses the automatic transmission fluid (ATF) to provide friction to partially translate the rotation of the engine into the gearbox. This is why automatics ALWAYS use more fuel than manuals - one revolution of the engine is NEVER one revolution of the gearbox.

The TCC is the Torque Converter Clutch, which is operated by a solenoid valve that locks the input and output sides of the torque converter together, effectively making the connection solid so that each revolution of the engine is directly transferred into the gearbox. It makes the thing more efficient, so the more often you can get your auto to do this, the more efficient it will be as the engine isn't losing revolutions.

The TCC (and the whole automatic gearbox) is controlled by the Transmission Control Module (TCM) which is a computer that lies in the bottom of the gearbox (yes, in the oil). It talks to the main computer to get information about vehicle speed, throttle position etc and decides what gear it should be in.

I hope I've explained that better.

As for towing in overdrive, you can easily - we hauled our 1.8T van through the desert last year in 40C+ heat in overdrive, it didn't have any trouble.

 

[crack]

thanks tony. so how do i know when the TCC locks? i thought the reason behind not towing in overdrive was the same as with manuals and towing in top gear, being to much load of the smaller gear?

 

[KraftyPg]

Coming in late but I agree with Tony, and the overdrive selection. I was towing 3.6t the other day and didn't once bother taking it out of over drive. On the flat it's barely an issue, you could tow an ocean liner if you could get it moving. On the hills it does make a difference but even hauling the 3.6t up the hill to the farm wasn't an issue and I never bothered taking out of OD. The Prado with the 2.5T limit and the 4L petrol is the same, stick it in drive, forget OD and drive it up the hill.

 

[crack]

i suppose if it cant pull it in overdrive its gonna knock back a gear itself anyway isnt it?

 

[KraftyPg]

Or pull the tow bar off the back of the ute and leave the trailer sitting on the road.

 

[Old.Tony]

Haha yes if the car can't haul in overdrive it will knock back a cog on its own.

To know when your torque converter is locked or not, try this easy experiment.

Go for a drive, leaving the car in overdrive the entire time. Cruise along at 50km/h, release the accelerator and look at the tacho. Now lightly press the accelerator just enough to maintain speed - the tacho will register a change in RPM.

Repeat the activity in the previous paragraph, but this time start at 80km/h. As you release the accelerator, the tacho won't move (it should sit around 1600rpm). As you depress the accelerator, the tacho again won't move much - it will only move slightly in exact proportion with vehicle speed.

Finally, while you're cruising at 80km/h, start to depress the accelerator more. As you pass 50% throttle, the torque converter should unlock, the car should kick down a gear and you will accelerate harder.

 

[crack]

ah righto i got ya. i have noticed that. thanks for all your help tony and krafty. now to just experiment a bit i suppose.

 

[Beergutz]

Crack,

I tow a scissor lift quite regularly all over the country side.(approx 2.5t. If you tow alot you may notice your rear suspnsion will sag. I recently had air bags installed to compensate and have notice a big difference in handling now that its back side isnt dragging on the ground. You must be careful not to over inflate though, something that has been brought up quite regular on here due to cracked chassis. I think common sense prevails there though. There are also other methods to help with rear suspension.

(Old.Tony, im pretty sure i ran into you at Kotara Shell the other day? didnt realise till i was driving out that it may have been you. Maybe one day ill catch up with you for a chat)

 

[crack]

cheers beergutz, yeh ive heard problems with airbags etc, and to make sure they ar eset up right. ive noticed the rear has saged allready with the steel tray ive put on. when funds permit ill be doing the suspension all round along with a bullbar etc.

 

[Old.Tony]

That's my local outlet, so it's very very likely it was me. Bonus is they've got cheap diesel and brand spanking new underground tanks - I'm not worried about contamination yet!

Christmas drinks are on this Friday still, I'll have to find the thread and bump it. Come along!

 

[rpm]

Hi Old Tony, Rpm Bunbury. If you drop down to 4th in the auto by locking o/d out, does the torque converter ever lock up????

 

[Old.Tony]

Hi Old Tony, Rpm Bunbury. If you drop down to 4th in the auto by locking o/d out, does the torque converter ever lock up????

It won't, the computer will only do it in overdrive. There are specific rules for it to happen, as you can appreciate the thing doesn't want to lock it up all the time - although I really can't see why not, if the vehicle is going to remain in a particular gear for some time.

I think it's new-ish technology for these guys, and eventually they might add it to other gears as well.

The manual (AT.PDF has a lot on this) basically outlines the following for the lockup to occur. Not meeting any of these will cause the computer to NOT lock up, and once locked, changing any one of these causes it to release:

* Vehicle speed is above 75km/h (roughly)
* Gear selector is in "D"
* O/D switch is ON
* Throttle is at or below 50%

 

[duck]

Gday can you be a bit more detailed about the lockup in 4th gear, I was on the understanding from the dealer that when towing do not use overdrive, I took that to mean press the unlock button on the on the auto leaver. I dont do this as I figured the auto will select the right gear when I am towing so when I feel it change down I then press the button so that the overdrive button light comes on meaning that overdrive is off, I was lead to believe that it now locks up the converter in 4th. Is that correct? I took your post to mean that leaving the button in overdrive would automatically lock the overdrive in 4th when it needed to change down from 5th to 4th. Can you clarify it with me? I assumed the switching off the overdrive the highest gear that it reaches is 4th which is a straight through gear. What position does the button need to be in to lockup the converter into 4th gear?

 

[Old.Tony]

While the dealer might have said "don't use overdrive", you are correct that the car will happily select the appropriate gear as needed and you don't need to worry about it.

Pressing the "Overdrive" button so that the "Overdrive Off" light is lit on the dash and therefore the gearbox is restricted to gears 1 through 4 will mean that the gearbox will NOT lock the torque converter.

The overdrive switch must be ON (dash light is NOT lit), the gear selector in D and the vehicle must be going fast enough for the gearbox to have selected 5th gear.

There is no mechanism that will allow the gearbox to lock the torque converter up in any other gear, unless you break into the TCM software, or intercept the signals going to the TCC solenoid and manually lock it up.

Notes:

The TCM (Transmission Control Module) is actually inside the bottom of the auto box. Drain the oil and remove the sump to get access to it.

If you choose to try intercepting the signal to the solenoid, be aware that there may be a check signal that the TCM needs to receive and any aberration may cause it to send a failure code to the ECU. Given that it's quite an important component, the failure may not just result in a "Limp Mode" condition (rpm limited to 2,000 and vehicle speed limited to 80km/h) but it may completely shut the vehicle down.

 

[duck]

Thanks Tony I will leave it overdrive all the time while towing our van usually all up weight about 2.2 tonnes. I was concerned with the auto not locked up and generating heat and cooking the auto oil which I may have been doing when I took it out of overdrive. I did ask the dealer to change the trans oil for the next service (70,000)as it spends most of the time towing. They say it is life time oil and does not need to be changed unless it is 'extreme' use so I decided not to persue it. It seems that Nissan service centres have this culture of telling D40 owners not to tow in overdrive as each time I have had it serviced in different states (WA, SA & NT) they have advised not to tow in overdrive
Thanks Duck

 

[johng]

There is no mechanism that will allow the gearbox to lock the torque converter up in any other gear, unless you break into the TCM software, or intercept the signals going to the TCC solenoid and manually lock it up.

Tony, I noticed last year that the US Pathfinders and I think Navaras provide Lock-up in the lower gears. Also, the service manual I have says that the Australian Petrol Pathfinders also lock-up in the lower gears. Bit late in the night to check now, but that's essentially what was set out. Pity the TCM can't be interrogated to change the parameters, eh?
John

 

[Old.Tony]

As long as it's the TCM doing the work, I'd be happy with it locking in lower gears but ONLY if I had positioned the lever in that gear (which is how the Pathy is probably configured).

Not that I want a Pathfinder box in my car, I'm happy enough with what I've got! If I get another Navara (which I might do, in the years to come), I'd be looking at this.

I wonder if the 550s lock up their torque converters in more than one gear?