Contents: Preliminary check ↳ Diagnostics of fluid leaks ↳ Gasket leaks ↳ Seal leaks ↳ Housing leaks ↳ Fluid is leaking from the vent tube… ↳
Note: failure of the automatic transmission can be caused by five main reasons: poor engine performance, incorrect adjustment, failure of the hydraulic system, mechanical problems, or failures of the computer and its supply network. Diagnostics should begin with checking the fluid level and its condition (see chapter 1), adjustment of the switch mechanism and the throttle mechanism. Then a "route" test is carried out to determine whether the problem has been correctly identified and whether further diagnostics are necessary.
Preliminary check
1. Warm up the gearbox to normal operating temperature.
2. Check the fluid level as stated in chapter 1.
a) if the fluid level is too low, add as much as needed, then check for external leaks (see below);
b) if the fluid level is too high, drain the excess, then check the drained fluid for contamination with coolant. If the automatic transmission fluid contains coolant from the engine, then the walls of the internal radiator separating the transmission fluid from the coolant are damaged;
v) if the fluid foams, drain it and refill the box, then check the presence of coolant in the gearbox fluid and its level.
3. Check the engine idle speed.
Note: Do not perform any checks if the engine is faulty - repair it first and get it running properly.
4. Check how freely the throttle cable moves. Adjust if necessary (section 6).
Note: The throttle cable may work fine when the engine is off and cool, but may fail when the engine is hot. Therefore, check it with the engine cold and normally warm.
5. Check the drive control mechanism (section 5). Make sure it is adjusted correctly and the mechanism operates smoothly.
Diagnostics of fluid leaks
6. Most fluid leaks are easy to spot visually: repair in this case involves replacing the seal or gasket.
Gasket leaks
7. Check the pan periodically Make sure all bolts are in place and tight, gaskets are in good condition, and the pan is flat.
8. A pan gasket leak can be caused by too much fluid level or pressure, blocked vents, pan bolts that are too tight, torn pan seal edges, damage to the sealing surface or the transaxle housing itself, damage to the gasket itself, cracks or defects in the castings of the transaxle itself.
Seal leaks
9. If the transmission seal is leaking, the cause may be too high a fluid level or pressure, clogged vents, damage to the seal bore, damage to or improper installation of the seal itself, a damaged surface of the shaft passing through the seal, or a loose bearing.
10. Make sure the dipstick tube seal is in good condition and the tube is installed correctly. Periodically check the area around the speedometer output for leaks. If transmission fluid appears, check the integrity of the O-ring. Also check the side gear shaft oil seals for leaks.
Housing leaks
11. If the housing itself is leaking, replace it.
12. Make sure the oil cooler hose ends are tightly installed and in good condition.
Fluid is leaking from the vent tube or filler pipe
13. Possible causes: the box is overfilled with fluid, there is coolant in the transmission fluid, the dipstick is faulty, the ventilation or drain holes are clogged.
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