Note. Incorrect operation of the automatic transmission can be caused by five main reasons: engine failures, incorrect adjustment, hydraulic malfunctions, incorrect operation of the mechanical part, or incorrect operation of the computer or its sensors. The inspection should always begin with detecting easily correctable problems: the level and condition of the hydraulic fluid (see chapter 1, section 4), adjustment of the lever mechanism and throttle travel. Then perform a road test to determine if the problem has been corrected or if further inspection is required. If after completion of preliminary checks and repair work the fault has not been corrected, then additional diagnostics must be carried out in the workshop.
Preliminary checks of technical condition
1. Drive the vehicle to warm up the transmission to operating temperature.
2. Check the fluid level as described in chapter 1, Section 4:
- a) If the fluid level is below the required level, add the required amount of fluid and then check for leaks.
- b) If the fluid level is excessively high, drain the excess and then check whether the drained hydraulic fluid contains coolant. The presence of coolant in the automatic transmission hydraulic fluid indicates that there is damage to the internal walls of the radiator separating the coolant and transmission fluids.
- c) If the transmission fluid is foaming, drain it and fill it with new fluid, then check it for coolant and see if the fluid level rises.
3. Check the idle speed. Note: If the engine runs rough, do not continue with the preliminary checks until it has been repaired and is running normally.
4. Check if the throttle cable moves freely. Adjust it if necessary (see chapter 4).
Note: The throttle cable may work normally when the engine is off and cold, but may not work properly when the engine is hot. Check its operation with the engine cold and warmed up to operating temperature.
5. Check the gear shift cable (see section 5). Make sure it is properly adjusted and that the linkage operates properly.
Checking for fluid leaks
6. Most fluid leaks can be easily detected visually. Repair usually involves replacing the seal or gasket. If the leak is difficult to find, the following procedures may help.
7. Make sure that it is transmission fluid that has leaked out, not engine oil or brake fluid (automatic transmission fluid is dark red).
8. Try to pinpoint the source of the leak. Drive your car for a few miles, then stop and place a large sheet of cardboard under the car. After a minute or two, you should be able to locate the leak area by the stain on the cardboard.
9. Carefully inspect the suspicious node and the area around it. Pay particular attention to the mating surfaces of the seals. In places inaccessible for direct inspection, you can use a small mirror.
10. If the leak is still not found, clean the suspected surface with a degreaser or solvent and dry it.
11. Drive the vehicle for a few miles, changing gears and maintaining normal engine operating temperature. After the trip, inspect the suspicious unit again.
12. After a leak is detected, before repairs are made, it is necessary to establish the cause of the malfunction. If you replace the gasket and leave the sealing flange deformed, then even a new gasket will not stop the leak. In this case, it is necessary to straighten the flange first.
13. Before attempting to repair a leak, check that the following faults have been corrected, as they may cause a new leak.
Note: Some of the faults described below cannot be repaired without experience and special equipment. Such faults need to be repaired in a transmission repair shop.
Leaking through gaskets
14. Check the crankcase periodically. Make sure the bolts are tight, none are missing, the gasket is in good condition, and the crankcase itself is not deformed (dents on the crankcase may indicate internal damage to the housing).
15. If the crankcase gasket is leaking, it is possible that the fluid level or pressure is too high, the vent is clogged, the crankcase mounting bolts are overtightened, the crankcase sealing flange is warped, the sealing surface of the gearbox housing is damaged, the gasket is damaged, or the cast parts of the gearbox are cracked. If a sealant is used instead of a gasket between the crankcase and the gearbox housing, it is possible that the wrong type of sealant was selected.
Leaks through seals
16. If the transmission seals are leaking, the fluid level or pressure may be too high, the vent hole may be clogged, the seal bore may be damaged, the seal itself may be damaged or improperly installed, the shaft protruding through the seal may be damaged, or the bearing may be "loose" and may allow excessive shaft movement.
17. Make sure the dipstick tube is in good condition and installed properly. Periodically check the area around the gear or speedometer sensor for leaks. If you notice transmission fluid leaking, check the O-ring for damage. Also check for leaks at the side shaft oil seals.
Leaks on the body
18. If the housing starts to leak, this means that pores have appeared in the cast parts and the housing needs to be repaired or replaced.
19. Make sure the oil cooler hose fittings are tight and in good condition.
Hydraulic fluid leaking through vent or filler tube
20. If this happens, it is possible that the transmission is overfilled, coolant has entered the transmission hydraulic fluid, there are pores in the housing, the dipstick readings for measuring the fluid level are incorrect, the vent hole is clogged, or the drain holes are clogged.
(The article was reprinted from the website «chevyman.ru»)