Monitor when auto torque converter locked up

[peter2904 Junior Member Find all posts View Profile Close peter2904]

Does anyone know if it is possible to monitor when the auto torque converter is locked up?
Guess there should be a signal to or from gearbox form the computer for torque converter status. If this could be monitored with a light on the dash then on big hills a lower gear could be selected or revs increased until torque converter is locked up to reduce chance of overheating.
(my first post on the forum)

[leachy_9 Advanced Member Find all posts View Profile Close leachy_9]

Re: Monitor when auto torque converter locked up

You should be able to tell just by watching the Tacho.

Leachy

[StormyKnight Advanced Member Find all posts View Profile Close StormyKnight]

Re: Monitor when auto torque converter locked up

Which lockup are you refering too?

The one around 1500-2000 rpm when the hydraulic efficiency of the torque converter means that nearly 100% of the power is being transferred thru OR

When the electronic clutch engages resulting in 100% power transfer..?

The first occurs at the same rpm no matter which gear, but is overriden by the second when it is engaged.

On the 4 speed auto (like mine), only in 3rd & 4th does the electronic lockup occur. It is easily seen on the tacho when accelerating & a gear change occurs. If the gearbox changes out of 4th into 3rd, the rpm will rise as expected & then a short time after the change (.5 sec or so) the revs will drop by about 500rpm. This is because the auto needs to disengage the lockup clutch before changing gears to make the change as smooth as possible, but it reengages it again after the gear change.

So basically if you are in 3rd or 4th, the lockup clutch will be enabled all the time even at full throttle, 2nd & first it will not be.

The 5 speed would be very similar but I'm not sure if the 3rd gear locks up or not.

Cheers

[peter2904 Junior Member Find all posts View Profile Close peter2904]

Re: Monitor when auto torque converter locked up

Thanks StormyKnight.
Other people have been saying to select a gear that keeps the revs over 2500 to prevent the slip heating up the gearbox.
Was trying to work out an easy way to tell if there is slip.

[StormyKnight Advanced Member Find all posts View Profile Close StormyKnight]

Re: Monitor when auto torque converter locked up

Well in 3rd & 4th (on the 4 speed) there is none at all. Please research for the 5 speed for your own piece of mind

Also whilst you can pull from 1800rpm, the auto usually won't let you stay that low under any sort of load anyway, so basically whatever the car chooses in terms of what gear its in you can be assured it is well within the safety guidelines for auto & engine longevity.

[cobbo150 Lurker Find all posts View Profile Close cobbo150]

Re: Monitor when auto torque converter locked up

Well in 3rd & 4th (on the 4 speed) there is none at all. Please research for the 5 speed for your own piece of mind

Also whilst you can pull from 1800rpm, the auto usually won't let you stay that low under any sort of load anyway, so basically whatever the car chooses in terms of what gear its in you can be assured it is well within the safety guidelines for auto & engine longevity.

The best useful instrument in this instance would be an automatic transmission oil temperature display, with high temp audible alarm. Early warning system.

An A/T oil temperature rise, would indicate torque converter slip. The engine temperature sensor has to much time lag to be of use in this case.

I have had two A/T oil temp episodes so far. Both circumstances were almost identical.

Different days, and different roads. Ambient temp 15c and 10c.

Both episodes involved long steep inclines, with low forward speeds.......about 30kph. (NOT towing).

First time.......auto was selected......allowed the box to do it's thing and change when appropriate.

Second time.....box was in manual (4th)......and box was allowed to do it's thing and change when appropriate.

During both episodes, engine temperature was normal and engine RPM was around 2000. Both roads were sealed.

Once the A/T oil temp light came on......I selected a gear to give 2500RPM and continued the climb (no where to pull over and blind corners). After 30/40 seconds the A/T oil temp light went off and continued the climb without problems.

From what I have observed, there seems to be a 200RPM difference between the A/T being locked or unlocked.

To confirm the above, I went over a similar road, using the gearbox in manual mode and keeping a forward speed of around 30kph and RPM at or above 2500, without any problems. No torque converter slip, due to box being locked.

Be aware the A/T oil light comes on, without any warning of temperature increase.

I feel sure, the heat build-up is linked to slow forward speeds and torque converter slip.

Once the box is locked, even at the same (low) forward road speed, temperature quickly drops and the A/T oil light extinguishes.

I feel that Toyota are onto the A/T oil temp issue and a field upgrade to the gearbox software will fix the sluggish change pattern. Read as.......A/T oil temp goes up, box downshifts to increase RPM.

The above comments are what I have experienced.

Regards,

[drecked Lurker Find all posts View Profile Close drecked]

Re: Monitor when auto torque converter locked up

Hi Peter I have a Ford Fairmont Ghia which has a button which slows down the auto gear change so it goes longer before changing gear
this is mean to be more economical ! but under normal circumstances the torque converter does not lock up in a vehicle because
than it would not operate properly !

[lawrance Senior Member Find all posts View Profile Close lawrance]

Re: Monitor when auto torque converter locked up

Was trying to work out an easy way to tell if there is slip.

An easy way to tell if the transmission's torque converter is locked or not is to curl your toes on the accelerator pedal and observe the tacho. If the revs don't flare up but is in a steady state, then the Torque Converter is locked up.

Lockup on the auto is only available in 4th and 5th gears, to the best of my knowledge.

Oh, and if you take your foot completely off the accelerator, say, when you are cruising steadily on the highway, the Toyota auto gearbox will automatically disengage the torque converter. You can observe this by the way the rev counter drops away to above idle. Stepping gently on the accelerator pedal sees the revs rise up to match the gear and then the torque converter locks again.

[barajak Senior Member Find all posts View Profile Close barajak]

Re: Monitor when auto torque converter locked up

I have been using a Scanguage to monitor water temps to get as early a signal that the auto is overheating. One of the few things the Scanguage cannot tell you is the transmission oil temp. I have noticed that the 150TD is using more fuel (up to 15%)below 1800rpm doing the same work under the same conditions than using a lower gear and keeping the rev up a bit. At the time the box overheated running uphill, were the revs below 1800? I now leave the box in S4 whenever I am going less than 90kmh and A when going faster. No more hesitation at intersections, no more vibrations at 1500rpm and better fuel economy.