trying to improve towing performance of 3l di auto

We have had the patrol for 3 years now as the tug for our caravan.
It is not a light van at 2400kg inc towball mass.
We are slowly leaning the peculiarities of the automatic transmission.
As most would be aware it 'hunts' constantly with overdrive on.
Also locks and unlocks constantly in 3rd with o,drive switch on (even though it is not overdrive) but stays locked better in 3rd with o-drive off.
Up a more than a modest hill i shift the lever back in 2 and stays locked even under acceleration.
So when we are towing we usually keep overdrive off and stay in 3, locked if possible. But this means higher engine revs and more noise especially over long trips.
On fairly level terrain i can usually keep the transmission locked in overdrive until i cant maintain speed above 77 to 80 ks.
I dont think there would be a large difference in the economy of towing locked in 4th or locked in 3rd as obviously the engine (and trans) has to work harder in 4th.
But which is better in the long run for the motor and transmission?
Do torque lockers make a discerable saving in diesel due to lower engine revs, longlivity of transmission oil and transmission itself due to cooler temperature of the transmission fluid?
Any comments, advice or personal experiences both positive or negative would be appreciated.
I plan having a transmission oil temperature gauge installed soon, so any advice along this line would also be appreciated
Cheers
Peter

Do you have an EGT gauge? I think you may find that the EGT will be lower with the OD off, it is with mine, and My camper is lighter at 1500kg.

No EGT gauge

I imagine by questioning if i have an egt gauge fitted implies that generated exhaust temperatures are more of a concern. I think the exhaust was upgraded or the turbo t off upgraded to 3" .
Sorry both were upgraded, so I'm told!

I don't tow a caravan or camper, but a trailer with all our camp gar on board. I have had the same issues that you talk about and find it best to always switch off the od, especially when passing, even more so on a hot day with the aircon running. I have had a couple of wake up calls half way past a truck on a hot day uphill, when it decided it didn't know which gear it wanted to be in. It's like going into limp mode and is really quite interesting. I get about 12 to 13 ltrs per 100 k and it doesn't really change much with or without od, although when the road is good and there is no traffic to navigate I put it in od. Seems to work ok for me. 2005 3ltr auto.


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The ZD 30 can be prone to high EGT, which may shorten its life.
Mine will go over 550c which is a safe limit, when towing up a hill, I also tow with the OD off.

So it seems the way i am driving at the moment is about the best way, economy is about 18l/100, so not the best. That really doesnt trouble me though i would like a little better, especially on the planned loop in a couple of years.
I gather by reading some forum topics that there are both pros and cons of the installation of a torque locker. Read mention of installing a resister, or changing the current one to help maintain lockup. But whereas this keeps the transmission fluid temperature down it would seem to have a negative impact on the exhaust temperatures?
Sorry if i sound naive but i am on a (steep) learning curve,!
Thanks paulyg and 4bye4 for your replies

Quote:

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Originally Posted by watto1416

So it seems the way i am driving at the moment is about the best way, economy is about 18l/100, so not the best. That really doesnt trouble me though i would like a little better, especially on the planned loop in a couple of years.
I gather by reading some forum topics that there are both pros and cons of the installation of a torque locker. Read mention of installing a resister, or changing the current one to help maintain lockup. But whereas this keeps the transmission fluid temperature down it would seem to have a negative impact on the exhaust temperatures?
Sorry if i sound naive but i am on a (steep) learning curve,!
Thanks paulyg and 4bye4 for your replies

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I would agree that driving it the way you are is probably the best way. Think about fitting a EGT gauge and a boost gauge and also a NADS before your big loop. The 3 ltrs seem to be prone to self destruction particularly on long towing trips. I say this in complete honesty in that I own one. I believe that looked after properly they can be as reliable as any other engine, but you should help it as much as you can. When reading the horror story's about these motors, remember that the people who have no problems seldom write up on the forums about it.

See my father inlaw has the converter lock up installed in his Prado and he locks it in 4th (5 speed auto box).
Hills etc he turns off the lock off but flat open road it's on..
This is with his 17' van..

Maybe worth installing a manual converter lock up and lock it in 3rd when towing..

I would have thought that you would never have the over drive on when towing.
I have a manual, I chose it because I tow a boat or car trailer, I never use 5th gear when towing.
A lower gear makes sense, less torque on input side of the gearbox for same power.
Graham