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Lock up torque converters

Submitted: Sunday, May 04, 2003 at 14:22

crowie

I have an auto Nissan ZD30 GU Patrol which like most autos these days has a lock up torque Converter ( LUTC). I presume that this, like most other things on this vehicle is electronicaly controlled via the engine management system. Fromresearch it seems that LUTC only lock over about 40kph and disconnect at about the same speed.

I found a site on the internet relating to Dodge Ram diesel which said that there is a simple aftermarket kit kit which allowes the driver to over ride the ECU and turn the LUTQ on and off with a switch in the cabin. Very handy I would think for additional engine braking on slow downhillers and for towing up slow steep hills, situations when the torque conveertor is not nornally locked..

Has anyone tried this with any auto and in partiular the ZD30 Patrol. Could it be done do you think there any potential dangers. Sounds like a simple and handy 4wd assist for offroad autos. but then again why hasn't it ben offered? Perhaps the Patrol does it anyway, I haven't tested it.
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AnswerID: 19148   Submitted: Monday, May 05, 2003 at 09:58

yarda replied:

In theory it would work, but the danger is that you would put excessive load onto the auto and without having a clutch, you would be able to stall the vehicle easily, also the engine tune for autos usually involves a higher idle setting and this would impede the ability to crawl downhill, the auto is actually pretty handy at climbing hills as you can use the slip of the torque convertor to your advantage, but downhill of course they aren't much good. Hope this gives you some usefull info, Brad
Reply 1 of 3
AnswerID: 19159   Submitted: Monday, May 05, 2003 at 10:48

GUPatrol replied:

Do some research and you will find that (like the Land rovers) the torque converter pattern is changed by the ECU as soon as you go into low range.
Once in low range and as soon as the rpm are higher than ?? the torque converter is locked by the ECU.
Most modern autos do that.
Will
Reply 2 of 3
AnswerID: 19178   Submitted: Monday, May 05, 2003 at 17:33

crowie replied:

Thanks for the responses. Will I'm sure your probably rightl and that preconditions for lock up are changed electronically in low range. I little bit more experimenting is needed. Perhaps Nissan has thought of everything!!! Its also right that the vehicle would stall like a manual if the TC was not unlocked at very low speed, though in the conditions I was thinking of, low range steep downhillers i guess the driver would just have to remember to switch the lock up off (like depressing the clutch) or change up a gear if and when engine braking overcame the slope and the vehicle started to stal.

I have read that most TC's unlock when the accelerator is released. For example going down hill in overdrive, foot off accelerator and so a certain amount of engine braking is lost. It would be nice in this situation to be able to keep the transmission locked and get a bit more engine braking in these sort of situations without the need to resort to brakes..

Apparently GM diesels with Allison overdrive autos have two modes: normal and tow/load. In normal mode lockup occurs in 4th and 5th but presumably in tow-load in lower gears and speeds.

I will experiment to asertain when lockup is occuring in different modes and try and get some techinical guff from Nissan or from someone with the official GUII manual.

Thanks again.
Reply 3 of 3