Zf Transmission Fluid Temperature Max

[nelsonian101]

What is the maximum safe operating temperature for the genuine ZF fluid?

I have done many circuit days with the ZF, but this will be the first I have done in Summer.

(Won't have an external cooler fitted until next year)

I have monitored the transmission temp with the SCT Xcal 3 software from Herrod on my laptop previously but only in winter.

I don't like to push the car to limp mode and prefer to prevent damage with cooldown laps if I catch it early enough.

Have been using a similar one to these Engine Watchdog sensors with Alarm for my coolant for years and will now be setting up a second one to a bolt on the ZF transmission cover to monitor the tranny temp. (Any where else I should put it?)

http://www.ebay.com.au/itm/180851532442?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Any opinions on what level I should set the alarm at for the tranmission temp too?

115 or 130degC?

Thanks.

[relentless xr6]

Hey mate I work on Allison transmission they are a truck automatic gearbox you will see alot of agitators with them we find our transmission operates best at 90 degree c I think at 105 degree c it's time to give it a rest IMO I'm dealing with truck autos which have massive clutch packs I hope I helped maybe it would be better to messure converter temps aswell.

[nelsonian101]

Was just thinking with the ZF oil in direct contact with the engine coolant via the larger F6 Heat exchanger;

could the Coolant be superheating the transmission oil? (or vice versa)

I let my coolant temp get to 115deg (with preset alarm) before coming into the pits.

[relentless xr6]

In truck autos our cooler has water going around the outside of the cooler so the transmission runs at engine temp which between 90-107 degree c I think you would be best putting a external cooler in the right hand fog light hole direct air to the cooler

[nelsonian101]

What ZF oil temp is reached before the car goes into limp mode?

120deg C?

[ScatterBrain]

I've had mine well over 160°c and it's never gone into limp mode, So it must be pretty high.

[arronm]

I am pretty sure it alarms at 120c and limp made at 130c.

[f-wolf]

http://www.4x4community.co.za/

An automatic transmission creates a lot of internal heat through friction: the friction of the fluid churning inside the torque converter, friction created when the clutch plates engage, and the normal friction created by gears and bearings carrying their loads.
It doesn't take long for the automatic transmission fluid (ATF) to heat up once the vehicle is in motion. Normal driving will raise fluid temperatures to 80 degrees C., which is the usual temperature range at which most fluids are designed to operate. If fluid temperatures can be held to 80 degrees C., ATF will last almost indefinitely -- say up to 160,000 Km. But if the fluid temperature goes much higher, the life of the fluid begins to plummet. The problem is even normal driving can push fluid temperatures well beyond safe limits. And once that happens, the trouble begins.

At elevated operating temperatures, ATF oxidizes, turns brown and takes on a smell like burnt toast. As heat destroys the fluid's lubricating qualities and friction characteristics, varnish begins to form on internal parts (such as the valve body) which interferes with the operation of the transmission. If the temperature gets above 120 degrees C., rubber seals begin to harden, which leads to leaks and pressure losses. At higher temperatures the transmission begins to slip, which only aggravates overheating even more. Eventually the clutches burn out and the transmission calls it quits. The only way to repair the damage now is with an overhaul.

As a rule of thumb, every 10 degree increase in operating temperature above 80 degrees C. cuts the life of the fluid in half!
At 90 degrees C., for instance, fluid life is reduced to 80,000 km. At 105 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 40,000 Km. At 115 degrees C., the fluid won't go much over 16,000Km. Add another 10 degrees, and life expectancy drops to 8,000 Km. Go 150 degrees C., and 1,600 to 2,400 Km is about all you'll get before the transmission burns up.

If you think this is propaganda put forth by the suppliers of ATF to sell more fluid, think again. According to the Automatic Transmission Rebuilders Association, 90% of ALL transmission failures are caused by overheating. And most of these can be blamed on worn out fluid that should have been replaced.

On most vehicles, the automatic transmission fluid is cooled by a small heat exchanger inside the bottom or end tank of the radiator. Hot ATF from the transmission circulates through a short loop of pipe and is thus "cooled." Cooling is a relative term here, however, because the radiator itself may be running at anywhere from 82 to 105 degrees C.!

Tests have shown that the typical original equipment oil cooler is marginal at best. ATF that enters the radiator cooler at 150 degrees C. leaves at 115 to 135 degrees C., which is only a 10 to 20% drop in temperature, and is nowhere good enough for extended fluid life.
Any number of things can push ATF temperatures beyond the system's ability to maintain safe limits: towing a trailer, mountain driving, driving at sustained high speeds during hot weather, stop-and-go driving in city traffic, "rocking" an automatic transmission from drive to reverse to free a tire from mud or snow, etc. Problems in the cooling system itself such as a low coolant level, a defective cooling fan, fan clutch, thermostat or water pump, an obstructed radiator, etc., will also diminish ATF cooling efficiency. In some cases, transmission overheating can even lead to engine coolant overheating! That's why there's a good demand for auxiliary add-on transmission coolers.

From:

http://www.4x4community.co.za/forum/showthread.php?t=69384

Edited 12/01/14 06:15 AM by f-wolf

[nelsonian101]

Great info there.

I recently had my ZF tune firmed up for a circuit day. Perhaps this extra friction on the clutch plates and a few WOT changes from 4th to 5th contributed to overheat the transmission quite quickly.

[old_mate]

Firm shifts = less slip = less heat. Last track day at QR in November there were a few 400rwkw cars that went into limp mode running stock exchanger setup, however mine with a external cooler never went above 105 degrees.