For info of GU 3.0Di AUTO owners who tow

Submitted: Friday, Jun 10, 2005 at 12:08
ThreadID: 23750 Views:2952 Replies:6 FollowUps:3
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Since I do a bit of towing I thought it would be useful to get one of those torque converter lock-up switches. In conversation with Rodney at Wholesale Automatics, he suggested I first fit a tranny temperature gauge so i could monitor what was happening and perhaps modify my driving style. So I did.

On Monday a mate and I had to do a quick trip up from Sydney to Warwick to deliver a race car on an open trailer and return next day with the empty trailer. The trailer loaded would have been approximately 2T and empty about 800Kg.

We found that the most heat is generated in the transmission towing at relatively low speed around town, particularly slowly climbing steep grades (50/60 KPH zones)where you are unlocked in second or third. Also on very steep highway grades where you are un-locked in 3rd at or below 80KPH. In any case the temp never rose beyond 90-100 Deg C.

On the highway using the correct driving style the temperature was well down to just registering on the gauge at 55-60 Deg C. Simply, do not engage overdrive until you have reached your cruising speed. At this point when you do, the converter will lock in 4th almost immediately. When you come to a lower speed zone or a grade where the converter unlocks 4th, simply disengage overdrive immediately the lock comes off. At speeds over 80 KPH the transmission will lock in third almost immediately and will hold lock in third above 80 KPH unless amost full throttle position is applied or speed drops below 80KPH. We were amazed at the grades we were going up locked in third at 90-100 KPH. The temp of course went nowhere because the converter was not in play. You only use around 400RPM more from being unlocked in 4th to being locked in 3rd and at 100 KPH this is still only 3000RPM which is a snack for the 3.0Di.

FWIW the trip was 800KM each way and we did it in 10Hrs each way including stops for meals, "relief" and fuel. We were definitely not driving for economy, striving to maintain the legal limit at all times. The New England highway has it's share of up hill and down dale as well. On the trip up (towing 2000KG) we averaged 15.07 L/100KM, on the return trip (800Kg) 13.6L/100KM. We only filled the tanks twice.

Of course you don't need the temp gauge to do any of this but it did help focus us on what was happening and determine the best driving style for this particular transmission. The added byproduct is that you are making best use of the power available and optimise your overall economy.

With this combo I don't think a lock-up switch would be of any real benefit because it was not really "hunting" by dropping lock in 4th unless there was a decent need for it. With a heavier trailer or one that pushes more air perhaps it would; so the jury is still out until I can test with a different trailer.
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Reply By: DEANO WA - Friday, Jun 10, 2005 at 15:04

Friday, Jun 10, 2005 at 15:04
cheers mate, just about to fit a lock up and youve done the research for me. towing a 16ft c/console around top end i'll think i'll need one.
AnswerID: 115253

Follow Up By: Outbacktourer - Friday, Jun 10, 2005 at 15:13

Friday, Jun 10, 2005 at 15:13
No worries, I'm not sure if I was clear in the note but I have not yet fitted the lock-up switch. The conclusion we came to was that with this particular trailer it was not worth it. Just simply toggling in and out of O/D with the standard button did the trick..
FollowupID: 370993

Reply By: motherhen - Friday, Jun 10, 2005 at 15:50

Friday, Jun 10, 2005 at 15:50
We tow a heavy van (18' Bushtracker). Nissan handles towing well but chews through the diesel. We went to have trans temp gauge fitted, but they said it already has an over temp warning light, so didn't fit it. They did fit the exhaust temp gauge (see previous posts re these gauges and temperatures people run at). Yet to try it towing the van and shudder at what temps it will reach; yet to ascertain "time to stop" temperature. We general put up with the high fuel consumption, and tow with OD off, unless on a real flat easy run. We bought the Nissan before the caravan; in hindsight probably should have chosen a bigger towing vehicle, but it is a heavy van. When we are not towing - which is most of the time, we have a nice comfortable vehicle.
AnswerID: 115264

Follow Up By: flappa - Friday, Jun 10, 2005 at 15:59

Friday, Jun 10, 2005 at 15:59
The problem with the warning light is by the time it comes on , its almost too late. Nothing better then actually being able to watch what IS happening.

I tow a campertrailer with my Auto Patrol and switch in and out of OD when needed.

Being the 4.5 petrol though , I do feel there would be an advantage in being able to lock it up. I do feel like it drops out sooner then it should at times.
FollowupID: 370999

Reply By: 4X4Treker - Friday, Jun 10, 2005 at 21:53

Friday, Jun 10, 2005 at 21:53
We tow a tamden axle Off Road Pratline which is fairly heavy and the way my wife packs it prob tips the scales close to 2T, I have only done one trip up to the Flinders with the new GUIV Auto but I found that the trans was unlocking a bit too soon in overdrive but as you said was OK in 3rd, I will be fitting a manual lock up to the trans as it will assist with towing under power thus reduce temp in trans but more importantly will also assist the engine braking.
A mate of mine (Chaz) has developed a good lock up circuit see 23653 and use link in Chaz's response to see his circuit. I have driven his GUIII with this lockup and it really works great.

AnswerID: 115304

Reply By: Chaz - Friday, Jun 10, 2005 at 22:22

Friday, Jun 10, 2005 at 22:22
Thanks Treker!
Outbacktourer, you are spot on with your temp testing. I had a trans temp gauge in my last 4by with manual lock up, and came to similar conclusions, however the main advantage with the manual lockup is to use it at lower speeds (below 80) in third and of course to eliminate the dreaded hunting that occurs when towing, as well as engine braking. I find myself using it in third at 60km/hour even when driving it around the city. The trans definitely runs cooler and the engine revs drop around 3 to 4 hundred rpm.
As you know your TCU will lock the trans above 80 in third and fourth as well as in Low first, but I find many other occasions where it is handy to lock it, particularly when I need maximum acceleration and engine braking, just like a manual. In short, it just gives you the best of both worlds, and it's a cheep and easy mod to do. If anyone is interested this is the Link to my circuit.

AnswerID: 115309

Reply By: muzzgit (WA) - Saturday, Jun 11, 2005 at 01:51

Saturday, Jun 11, 2005 at 01:51
When on holidays I tow a Jayco Penguin, approx 1200kg, plus gear in the car when loaded. I checked with Nissan and Toyota before I purchased my 3.0 patrol (was also looking at auto prado). Both recommend to NOT use OD while towing or with load over 750kg.

On our first trip we went from perth to broome, around the place and back and only used OD when needing extra speed passing road trains.

We trundled effortlessly up some pretty good hills in 3rd and basically kept speed under 100.

I found that trying to keep locked in 4th I was pushing the pedal pretty hard and the motor seemed to be labouring more, plus the speed kept creeping up over 120. Some people aren't woried by this but I'm ever aware of furry critters that jump out in front of you so I like to be not going so fast. Plus, I like having a license.
AnswerID: 115324

Reply By: angler - Sunday, Jun 12, 2005 at 21:16

Sunday, Jun 12, 2005 at 21:16
Thanks for the info on temperatures reached in the auto box. I have been wondering about what it actually gets up to. We tow a 2.2T van with our 3 litre auto and have found it does a bit af a hunt in and out of ock every now and then . I just keep it in drive most of the time and it seems to sort itself out. We averaged about 15 to 16L/100 towng the van to Darwin last year and the patrol went really well.
I too am looking at a lockup system and will put in the manual one first then shift to an automatic speed sensing one when I get it working. Shouldn't be too long now.

For Chaz, the instructions at the start say to splice into the solenoid wire. I assume you mean to cut it, then insert the relay contacts as per the diagram.
AnswerID: 115482

Follow Up By: Chaz - Monday, Jun 13, 2005 at 17:14

Monday, Jun 13, 2005 at 17:14
Yes, that is correct. I'm sorry, I shouldn't have used the term "Splice"
I may have to change the wording to "Cut"
The whole circuit virtually goes in series with that green wire between the TCU and the converter solonoid.
Good Luck!
FollowupID: 371206

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