Effect of the Torque Converter in Real Life?

[carbon60]

I've been studying how my '96 FZJ80's A343F transmission works, including how the little buttons (O/D, PWR, 2ND) and the transfer case effect me in real life. And I'm confused about when the torque converter is needed?

Example A:

Driving fast [as I can] through twisty trails, generally staying between 20 kph (12 mph) and 50 kph (30 mph).​

Conclusions and questions during example A:

1. Transmission runs much warmer in HI than in LOW, pretty much 90ºC (194ºF) in HI and 50ºC (122ºF) in LOW; (I have a gauge on it.) The engine temperature is also affected by about 8ºC (14ºF) in this case. Does this temperature difference matter at all?
2. Disabling overdrive should allow the torque converter to lock up in third, but what effect should that have in real life? I don't fully understand when I want torque multiplication.
3. Does having higher shift points via the PWR button result in less load on the engine and less transmission heat since the torque converter is not working as hard?
4. If in LOW, enable 2ND makes for smoother starts when I don't actually need the low gear.
5. What is going to result in the least fuel consumption, or will it make any real difference?

Example B:

Low speed work on obstacles, in LOW.​

Conclusions and questions during example B:

1. I generally keep the transmission in L, but maybe I should be leaving it in D and using PWR to avoid quick upshifts while still benefitting from the automation?
2. Since I'm never going to get to 4th in the case, I should leave O/D disabled to benefit from the lock up while in 3rd? Or do I actually want the torque multiplication in most cases, anyway?

General notes:

My rig is heavily loaded almost all the time, weighing around 3000 kg (6600 lbs).

Thanks for any and all input.

A.

 

[Wayne]

carbon60, this sounds like a mechanical engineering question. I'll admit, I don't know. I'm going to watch this thread and see what some of the more enlightened Mudders have to say. Sorry, no help here.

 

[hammerheadfistpunch]

The Converter is doing to do its thing the way its going to do it and there isn't going to be much risk of burning it up unless you are out of stall for a long time (going up a long steep hill at low rpms or in heavy mud), in which case you want to find a way to bring the rpms up so the converter is closer to stalling if not locked. i.e. its not worth trying to manipulate the converter artificially, just use your noodle; lots of load? use revs. The torque multiplication really only comes into play moving away from rest, as that's when the highest slip in the converter occurs. Think of it sort of like riding a clutch; more slip means more revs means more power. its not technically a torque multiplication as much as its just trading distance for engine speed - like regearing - in that you aren't getting more torque from the engine, but your engine is allowed to spin faster than its gearing would normally allow meaning you get more power (hp =(torque x rpm)/5252) which means more force applied to the road. More slip means more friction which means more heat. So if it was a standard transmission your brain would learn and adjust to what the slip/heat tradoffs would be and you would use it when you needed and avoid it when you don't. The converter does the same thing but automatically.
I don't know much about the A343f converter, but I don't seem to hear a lot of burnt out converters or burnt out transmissions from overheat. The A343F is pretty stout and well matched for our trucks. Yes, a heavy truck will generate more transmission heat but its all pretty well controlled.

General rule of thumb:

To keep trans heat low, stay about 2500 rpm with a heavy load. typically speaking, stall speed on a converter should be 700 rpm lower than the torque peak, which is between 3000-3200 for the 1fz depending on which source you think is accurate and so the converter should be hydraulically stalled or close to stalled above 2500 or in locked mode, minimizing heat build up. above 1st gear speeds, the energy needed to move the truck is less than from a stop and so there is less need of torque multiplication and less heat build up. Long story short - don't worry past 1st gear too much

FYI - The Transmission locks out OD in low range anyway so there is no need to turn it off.

 

[Howard705]

The torque converter always has slip UNLESS LOCKED (which came out to increase effeciency and save fuel) The PERCENTAGE of slip is higher under lower rpms (and under more load)-like a boat prop-you can hold the boat at idle (all slip) but try that when it's at peak rpm. The "slip" goes down as the rpm goes up. (and the load down) The head generated is wasted energy also.

 

[hammerheadfistpunch]

The torque converter always has slip UNLESS LOCKED (which came out to increase effeciency and save fuel) The PERCENTAGE of slip is higher under lower rpms (and under more load)-like a boat prop-you can hold the boat at idle (all slip) but try that when it's at peak rpm. The "slip" goes down as the rpm goes up. (and the load down) The head generated is wasted energy also.

This is true, but at stall its slip is very small.

 

[Howard705]

A few percent but enough to warrant lockup converters. Never had a scanner on my 80 but on gm 4l60e. Towing as soon as the tc unlocks heat starts rising fast. If i downshift it ahead of time on hills the tc stays locked and temp doesnt budge. Heat is your enemy.

 

[SJWantsADiesel]

My LX450 has 35” tires and moderate load with an ARB style bumper and rear metal bumper. Going up on windy roads, in H, the tranny temp gauge went up to 150F. Usually hangs around between 90-110F on the freeway. Is that normal? And, how should I be driving on hills/windy roads to keep the temp low? Thanks.

 

[baldilocks]

My LX450 has 35” tires and moderate load with an ARB style bumper and rear metal bumper. Going up on windy roads, in H, the tranny temp gauge went up to 150F. Usually hangs around between 90-110F on the freeway. Is that normal? And, how should I be driving on hills/windy roads to keep the temp low? Thanks.

150 up hill is normal. My A442f usually runs 130-140 until the going gets tougher. I’ve seen 170 on the trail; a short break brings it down quickly.

The pick-up in my signature runs a trans temp of 150 on the easiest of drives. The fluid needs to warm up enough to evaporate moisture.

There is a lot going on in you’re opening post and perhaps too much t be concerned about. I do have an answer to your 5th question: drive a different vehicle.

 

[Marco Lau]

keep in mind the super hot tranny oil is first entered into the bottom of the radiator for cooling prior to entering the transmission oil cooler. This will most likely results in increase in coolant temp. when you are already struggling to keep the engine temp low during these slow wheeling conditions.

 

[baldilocks]

A few percent but enough to warrant lockup converters. Never had a scanner on my 80 but on gm 4l60e. Towing as soon as the tc unlocks heat starts rising fast. If i downshift it ahead of time on hills the tc stays locked and temp doesnt budge. Heat is your enemy.

This is exactly why I love my Cummins. Keeping the TC engaged at all times above 25mph is possible and she hunkers down to get the job done with real torque while the trans temp stays low.

 

[Gilles75]

The Converter is doing to do its thing the way its going to do it and there isn't going to be much risk of burning it up unless you are out of stall for a long time (going up a long steep hill at low rpms or in heavy mud), in which case you want to find a way to bring the rpms up so the converter is closer to stalling if not locked. i.e. its not worth trying to manipulate the converter artificially, just use your noodle; lots of load? use revs. The torque multiplication really only comes into play moving away from rest, as that's when the highest slip in the converter occurs. Think of it sort of like riding a clutch; more slip means more revs means more power. its not technically a torque multiplication as much as its just trading distance for engine speed - like regearing - in that you aren't getting more torque from the engine, but your engine is allowed to spin faster than its gearing would normally allow meaning you get more power (hp =(torque x rpm)/5252) which means more force applied to the road. More slip means more friction which means more heat. So if it was a standard transmission your brain would learn and adjust to what the slip/heat tradoffs would be and you would use it when you needed and avoid it when you don't. The converter does the same thing but automatically.
I don't know much about the A343f converter, but I don't seem to hear a lot of burnt out converters or burnt out transmissions from overheat. The A343F is pretty stout and well matched for our trucks. Yes, a heavy truck will generate more transmission heat but its all pretty well controlled.

General rule of thumb:

To keep trans heat low, stay about 2500 rpm with a heavy load. typically speaking, stall speed on a converter should be 700 rpm lower than the torque peak, which is between 3000-3200 for the 1fz depending on which source you think is accurate and so the converter should be hydraulically stalled or close to stalled above 2500 or in locked mode, minimizing heat build up. above 1st gear speeds, the energy needed to move the truck is less than from a stop and so there is less need of torque multiplication and less heat build up. Long story short - don't worry past 1st gear too much

FYI - The Transmission locks out OD in low range anyway so there is no need to turn it off.

I'm coming back to a very old topic but I'm experiencing some issues with the stall speed. My 1HDFT combined with A442F trans stalls at 1400 rpm (this is obviously way before the turbo kicks in and therefore its difficult to climb hills from standstill). I have replaced the torque converter with a new one (heavy duty bought from Wholesale Automatics) but not much change. Could there be any other reason for the engine to stall at too low rpm? The engine is quite strong and powerful from 2000 rpm upwards.

 

[baldilocks]

Is the converter stalling or is it being told electronically that it’s time to lock the convert clutch when, actually it’s too soon.

It would seem that the converter itself was never the problem to begin with.

 

[Gilles75]

Yes so it seems. But where to look now for the issue? Stall speed at 1300 rpm isn’t correct, right? Any pointers or suggestions are highly appreciated.

 

[Gilles75]

Hello all,
anyone have some suggestions on where to look for the issue that I have? The torque converter is all fluid based with no electronics. Is it gearbox or engine related that my car stalls at 1300 rpm (instead of 1900 rpm which is factory specification).

 

[Lumpskie]

Hello all,
anyone have some suggestions on where to look for the issue that I have? The torque converter is all fluid based with no electronics. Is it gearbox or engine related that my car stalls at 1300 rpm (instead of 1900 rpm which is factory specification).

I would post over in the diesel section for more/better answers. I think the fully hydraulic A442f may have only came with the diesels... I also have the same transmission as you (Wholesale Automatics A442f). All I can tell you is that stall on mine occurs around 2000 RPM (as you called out as in spec). I'm not sure on how to answer your question... this is my first automatic vehicle.