torque converter stall test

[shogun]

A "stall test" can be used on many transmissions to check its ability to hold torque and the operation of the converter one-way clutch. Some manufacturers don't recommend using a stall test because it stresses the transmission, so if you use this procedure, do not do it for more than five seconds at a time.

Before conducting a stall test, check the fluid level and condition. Chock the wheels and set the parking brake. Start the engine and place the transmission in drive while holding the brake pedal under firm pressure so the vehicle doesn't move. Then push the accelerator to the floor while holding the brakes on. Note the maximum rpm that the engine reaches. This is the stall speed. If it is lower than specifications, the torque converter one-way clutch is slipping. If the stall speed is higher than specifications, the transmission is slipping. Possible causes include a low fluid level, restricted fluid filter, a sticking pressure regulator valve, slipping clutches, bands, shaft splines or one-way clutch.

Most late-model automatics have some type of lockup torque converter to improve fuel economy. If the lockup fails to engage, there will be some slippage and fuel economy will drop. Causes here include a bad lockup solenoid, incorrect sensor input information to the transmission controller or PCM (typically a speed sensor) and hydraulic control problems. If the lockup fails to release, the engine may shudder and die when coming to a stop. Causes here include a faulty lockup solenoid, a sticking lockup valve, grounded lockup solenoid wiring or a missing lockup solenoid spacer plate screen.


Lockup shudder is another complaint that may be encountered. This refers to a vibration that is felt just before or after lockup occurs. This kind of problem can be hard to diagnose because the cause may be the torque converter, transmission or engine. Bad motor mounts, engine misfire, a bad CV joint or

U-joint, etc. can all cause vibrations that may be felt as a shudder throughout the drivetrain.

Another problem that affects the operation of the torque converter is a condition called "transmission drainback." One-way check valves normally keep the torque converter full of fluid when the engine is shut off. But if the transmission input shaft bushings are worn, it can create a path for fluid to drain out of the converter back into the transmission. The loss of fluid from the torque converter can make the transmission feel as if it is slipping on initial take-off for about five to 10 seconds.

If a torque converter fails a stall test or is leaking, it must be replaced. Many experts also recommend replacing the torque converter if an automatic transmission or transaxle has failed and is being replaced. Why? Because the torque converter acts like a garbage pit and traps a lot of the debris that results from normal wear. The debris may then contaminate and damage the new transmission. Why not just rinse out the old torque converter with solvent? The design of the wheels and large surface area inside the converter make it very difficult to clean.

By the time most transmissions need to be replaced, the friction linings inside a lockup converter are reaching the end of their service life. Reusing a lockup torque converter with worn linings is asking for trouble. And since there's no easy way to open up and clean or rebuild the internal components (doing so requires cutting open the housing on a lathe and rewelding the housing to seal it back up), replacement is your only option.

When replacing a torque converter, the replacement unit should have the same stall-speed rating as the original (unless you're installing a performance converter with a higher stall-speed rating). Too low a stall speed can lug the engine and overwork the transmission, while too high a stall speed can increase fuel consumption. When the new torque converter is installed, pour a quart or two of fluid into the unit before bolting it in place. This will protect the bearings and thrust surfaces during the initial startup until pressure from the transmission refills the unit.

AUTOMATIC TRANSMISSION REPLACEMENT TIPS
If a diagnosis reveals internal transmission problems that require replacing the transmission, here are some tips that can prevent comebacks:

Flush out the ATF oil cooler lines to make sure they are clear and contain no debris (very important if the transmission has failed due to overheating or contains contaminated fluid).

Recommend adding an auxiliary ATF cooler if the vehicle is used for towing, off-roading or racing. Keeping fluid temperatures within safe limits will help prolong the life of the transmission.

Use the type of ATF specified by the vehicle manufacturer when refilling the transmission. Honda, Mercedes-Benz and others all have their own unique fluid requirements. Make sure the ATF you use meets OEM specifications.

Read the installation instructions that come with a reman transmission. Some applications may require special care to align dowel pins, a special adjustment procedure for the throttle valve cable, etc.

On applications with diesel engines and mechanical vacuum pumps, make sure the pump is working correctly and that all vacuum lines are correctly routed.

On rear-wheel-drive cars and trucks, inspect the U-joints in the driveshaft. On front-wheel-drive cars and minivans, inspect the CV joints and boots. Replace any parts that are worn or damaged.

Pay close attention to the condition of the motor and transmission mounts, especially fluid-filled hydroelastic mounts. Replace any mounts that are cracked, loose or leaking.
AUTOMATIC TRANSMISSION FLUID (ATF) SERVICE TIPS
Many transmission experts say most transmission problems can be prevented by changing the transmission fluid and filter regularly as preventive maintenance. How often depends on how the vehicle is driven. For some vehicles, this might be every 30,000 miles or two years.

The harder the transmission works, the hotter the fluid runs. The life of the fluid drops quickly once its temperature gets up above about 200° F. ATF also becomes contaminated with normal wear particles from the clutch plates, bushings and gears. The filter will trap most of this debris before it can cause problems. But many older Asian transmissions only have a plastic or metal screen that does little to protect the transmission against internal contaminants and nothing to keep the fluid clean. On these vehicles, changing the fluid is the only way to get rid of these contaminants.

Changing the fluid by dropping the transmission pan can leave up to three or four quarts of old, oxidized fluid inside the torque converter. A better way to change ATF is to use equipment that exchanges new fluid for old while the engine is running. Such equipment can usually replace up to 90 percent or more of the old fluid.


More info under this link:

Automatic Transmission Related Links:
AAMCO transmission shops
ATK Remanufactured Transmissions
Automatic Transmission Rebuilders Assn. (ATRA) (Search for ATRA member shops in your area)
BMW Transmission Service Information
Ford Transmission Applications
Jasper Transmissions
Transmission Digest magazine technical articles
Transmission Rebuilders Network Worldwide
Transmission & Torque Converter Application & Identification Guide
Valeo Transmission & Clutch Troubleshooting Tips

http://www.aa1car.com/library/2003/ic60340.htm

[WolfStrong]

Interesting. Never did a test, but I can already tell you mine is on the end of its life. This is exactly what mine seems like:

Another problem that affects the operation of the torque converter is a condition called "transmission drainback." One-way check valves normally keep the torque converter full of fluid when the engine is shut off. But if the transmission input shaft bushings are worn, it can create a path for fluid to drain out of the converter back into the transmission. The loss of fluid from the torque converter can make the transmission feel as if it is slipping on initial take-off for about five to 10 seconds.

If I start it right up, and start to drive, the car has to rev a bit before it starts moving. However, let it idle for maybe 30 seconds to a minute and it is up to what I consider normal. Regardless, my next one will be a stick as I am very disappointed in the auto performance.

[LouieD]

Very good info.

[m60b30530i]

glad to know that the 530ia's torque converter is still good.

[shogun]

we cut one off from an E32 Alpina B12, here the pics
http://www.bimmerboard.com/forums/posts/538360/

We have a small shop here in Yokohama/Japan which rebuilds them for us.
The symptoms were slippage under sudden strong acceleration and occasional juddering
looks as if the clutch material had completely disintegrated and it was direct steel on steel contact

[shogun]

Did somebody ever make such a stall test?
Here is another instruction for the WRX http://ken-gilbert.com/wrx/STi_Manua...all%20Test.pdf
Attempt to finish the stall test in as short a time as possible, in order to prevent the automatic transmission from sustaining damage.

Torque Converter Stall Test

If the torque converter stators one way clutch is suspected of slipping or being seized a torque converter stall test should be performed before bench testing the converter. Always check with vehicle manufacturer before performing this test.
http://www.freeasestudyguides.com/to...tall-test.html


More trans related info/bulletins here http://www.europeantransmissions.com...MWtechinfo.htm

[locknload]

Might also put this in the FAQ under, "How can I tell if my guibo will need replacing soon?"

[shogun]

stall test 4HP22_24 for Landrover, which also has the 4HP22_24

Testing
1. Chock the wheels and fully apply the handbrake.
2. Start the engine and run it until it reaches normal operating temperature.
3. Apply the footbrake and select 'D'.
4. Fully depress the accelerator pedal and note the tachometer reading. The figures should be as given below. Do not carry out stall test for longer than 10 seconds, and DO NOT repeat
until 30 minutes have elapsed.

V8: 2200 to 2400 rev/min
Diesel: 2600 to 2800 rev/min
5. A reading below 1300 rev/min indicates a torque converter fault, ie stator free-wheel.
6. A reading between 1300 and 2200 rev/min (V8) or between 1300 and 2600 rev/min (Diesel) indicates reduced engine power.
7. A reading above 2400 rev/min (V8) or above 2800 rev/min (Diesel) indicates clutch slip.
NOTE: The figures quoted above were measured at sea level with an ambient temperature of 20°C (68°F). At higher altitudes or higher ambient temperatures, these figures will be reduced.

http://workshop-manuals.com/landrove...ts/stall_test/