Cruise Control towing (D3) ??

[gps-au]

Hi Folks,

I am currently traveling up the east coast from Sydney to Cairns.
Whilst in Brisbane I picked up a 12 x 6 fully enclosed "furniture" van (tandem) trailer.

Apart from the shock of fuel consumption with dragging a large slab sided box, its currently empty (It will be full going south to Sydney in a week of so). Trying to maintain speed limit, I notice that the cruise is having trouble on some of the long hills, kicking down from 5th to 4th, & a few times the cruise control dropping out. (It seems that it wont even try to drop to 3rd (I have been manually dropping it).

Is this usual behavior ?

My previous heavy towing really didn't have the hilly terrain and was much more streamline.

[Rockylizard]

Gday...

I tow a 2600kg van full time. When towing on flat to slightly undulating terrain I use Cruise Control in Drive set at 1900rpm @ 89-90kph. At that speed the auto sits in 5th and only changes down to 4th (2500rpm @ 89-90kph) on the uphill bits.

However, in anything hilly, I have found it is best not to use Cruise Control and just drive it on the tach. I then hold it around 2000-2500rpm and let the auto determine what gear it wants and let the speed drop to whatever the auto's gear choice is. If that means 2000-2500rpm means 40kph on very long hills then so be it.

I use Command Shift and hold it in 3rd (and sometimes 2nd) on down hill runs to help hold the speed. Occasional dab on brakes is required, but better than riding brakes in Drive and wearing/overheating them out.

D3 (TDV6) gives me an average of 14.5ltr/100km with a best of 12.1ltr/100km on long fairly flat run - to 16.0ltr/100km in very hilly country (or strong head winds).

I reckon the D3 pulls the weight effortlessly really. Very little throttle pressure needed to hold 2000rpm up hills (although it may get down to 40kph on really long ones)
.
Cheers
John

[roamer]

Check the wheel bearings and brakes on that trailer, empty you should barely know its there.


Cheers Ken

[peterall]

I agree with the Lizard...Cruise control seems a bit too aggessive when towing so I use auto on the flat country and Command Control on the hilly areas. The auto also tends to hold 5th a bit too long so a quick flick on the command control to maintain 2000-2500 is good and easy.:)

[KOOS BEST]

After I have owed 2 x Patrols fitted with EGT gauges, and now a D3 TDV6 I will never tow with cruise control again.
The EGT climbs miles high even in nearly flat terrain to maintain the set speed. What actaully happens the systems starts overfueling to stay at the speed even in long not so steep inclines.
My experience is that you never tow a heavy load with a diesel powered engine using cruise control.
The D3 D4 have fantastic ECU that controls the EGT , so when it gears up and down and hardly gets to 6th gear there is a reason, the reason is its controlling the EGT.
You guys down under have the same scenario as us here , high ambient temperatures, so if you have ever driven a diesel vehicle in 35 deg C and above and set it on cruise control, you wont believe your eyes looking at the gauge, the engine operate far above the normal threshold it can tolerate.
Luckily the D3 D4 ecu as said controls that , but I rather tow without using the Auto box to decide except downhill I will use command shift.

[RichardK]

If I recollect correctly the manual does not recomend towing with the cruise control

[gps-au]

Thanks ALL of you.

I jacked up each side of the trailer today (its a hire) and checked brakes and bearings, one axle was a bit on the dry side, whilst the second I could only say was fine.

I then took it for a 50km run and the "slabness" was definitely apparent, I then adjusted my tow ball height (about 50mm higher) to get the trailer level, and bingo all the "apparent" drag seemed to disappear and the cruise control then acted more "normal".

I would never had thought that leveling the trailer would have had such a dramatic effect.

At least the majority of the run home is "flat" in comparison to the run up as I'll be going inland (much shorter).

Yes it would be a lot more economical to slow down, but by necessity, this is a quick trip, not my more leisurely "holiday" drive.

Only problem so far to solve is my adjustable height tow tongue, which when raised interferes with opening the rear due to being in the way of the wheel carrier locking handles (Kaymar), looks like I'll just grab another tongue in the morning. (Actually I just realised that if I hadn't shortened the square section, I probably wouldn't have the problem, but I just hated then extra 8 inches it pushed the ball back.

<edit>
Silly me, I forgot the trailer will ride lower once loaded, so I can drop the ball height a notch which will then clear the wheel carrier handles (BTW, its a mitch hitch so much higher).
</edit>

[Preacher]

I read this post last week before going to the Flinders with my new to me 12 ft poptop offroad van.

All up weight under 1800kgs - averaged 18lt /100km travelling between 90 - 110 km/hr - flat to undulating countryside.

Most of the time it travelled in 5th (on cruise control) in manual was the same, very occasionally I'd drop it into 6th going downhill or on a long flat - but mostly it liked 5th.

Tyre pressure was 35psi front 38psi rear and 35 on the van (also with muddies)

18lt/100 seemed very heavy to me, however with a rooftop tent and 265 65 17 Maxxis bighorn muddies on (normal fuel is 12.5 -14) I guess it's not too bad.

Any thoughts

[gps-au]

my final wash on this one...

Night drive south of Roma to Surat.
Overtook semi, and cb burst to life...

"hey did you know your left front wheel is sparking ?"

Me: "I hope your refering to the trailer, or else I am in big trouble !"

"yeah, the trailer"

Me: "thanks"

OK, so its a tandem, so whats the worst which could happen over the next 20km to surat ? that I arrive with the trailer on 3 instead of four wheels.

OK upon arrival met with that particular burnt metal smell we all just luv (not).

Next morning had a look, seems the wheel was only held on by the brake disk. Took it down to Bayly's and had the front wheel bearing replaced.

Now I was intrigued to also notice that some time in the past the left front spring had been replaced,,,, mmmm

Ok Getting back to Sydney, put full trailer on weighbridge, 2.08t, unhitched, hitched 2.04t WHAT 40kg ball weight !!

next day weighed empty trailer 1.1t.

So it definately wasn't overloaded.

funny how the hire mob wasn't surprised about the bearing (& refunded).

[Redback]

I read this post last week before going to the Flinders with my new to me 12 ft poptop offroad van.

All up weight under 1800kgs - averaged 18lt /100km travelling between 90 - 110 km/hr - flat to undulating countryside.

Most of the time it travelled in 5th (on cruise control) in manual was the same, very occasionally I'd drop it into 6th going downhill or on a long flat - but mostly it liked 5th.

Tyre pressure was 35psi front 38psi rear and 35 on the van (also with muddies)

18lt/100 seemed very heavy to me, however with a rooftop tent and 265 65 17 Maxxis bighorn muddies on (normal fuel is 12.5 -14) I guess it's not too bad.

Any thoughts

If you have a TDV6, then I would say that's a bit high, you should be getting around 14l to 15l/100k, going on other TDV6 owners on here.

Baz.

[gghaggis]

With muddies and the roof-rack, I don't think you'll get much better than 16 to 17l/100. If you sit at a constant 90kph as opposed to 110kph, you'll be surprised at how much fuel you save, but it does seem to take forever to get anywhere!

Cheers,

Gordon

[gps-au]

If you sit at a constant 90kph as opposed to 110kph, you'll be surprised at how much fuel you save, but it does seem to take forever to get anywhere!

Especially on the open road and at night (with no animals or other vehicles in sight) !!

[Duck's Guts]

Gordon & Baz areright on the money...

My experience is: 2.7TD, Bighorns, 3/4 roof rack, single axle offroad poptop c/van with A/T tyres =

14-15l/100kms at 90km/hr
16-17l/100km at 100-110km/hr