Initial Inspection and Diagnostic Overview
TORQUEFLITE DIAGNOSIS AND TESTS
DIAGNOSIS-GENERAL
Automatic transmission malfunctions may be caused by four general conditions: poor engine performance, improper adjustments, hydraulic malfunctions, and mechanical malfunctions. Diagnosis of these problems should always begin by checking the easily accessible variables: fluid level and condition, manual linkage adjustment, and throttle linkage adjustment. Then perform a road test to determine whether the problem has been corrected or that more diagnosis is necessary. If the problem exists after the preliminary tests and corrections are completed, hydraulic pressure tests should be performed.
Fluid Level and Condition
If a failure of any kind has contaminated the transmission fluid, the oil cooler and cooler tubes must be reverse flushed (see "Oil Cooler and Cooler Tubes Flushing.")
Before removing the dipstick, wipe all dirt off of the protective cap and top of the filler tube. Since the torque converter fills more slowly in the "P" Park position, place the selector lever in "N" Neutral to be sure that the fluid level check is accurate. The vehicle must be on level ground. The engine should be running at idle speed. The fluid should be at normal operating temperature (approximately 175 F). The fluid level is correct if it is between the "Full" and "Add" marks on the dipstick.
Low fluid level can cause a variety of conditions because it allows the pump to take in air along with the fluid. As in any hydraulic system, air bubbles make the fluid spongy, therefore, pressures will be low and build up slowly.
Improper filling can also raise the fluid level too high. When the transmission has too much fluid, the gears churn up foam and cause the same conditions which occur with a low fluid level.
In either case, the air bubbles can cause overheating, fluid oxidation, and varnishing, which can interfere with normal valve, clutch, and servo operation. Foaming can also result in fluid escaping from the transmission vent where it may be mistaken for a leak.
Along with fluid level, it is important to check the condition of the fluid. When the fluid smells burned, and is contaminated with metal or friction material particles, a complete transmission overhaul is needed and because the torque converter cannot be flushed, it should be replaced. Be sure to examine the fluid on the dipstick closely. If there is any doubt about its condition, drain out a sample for a double check.
After the fluid has been checked, seat the dipstick fully to seal out water and dirt.
OIL COOLERS AND TUBES FLUSHING
When a transmission or lock-up clutch failure has contaminated the fluid, the oil cooler(s) should be reverse flushed to insure that metal particles or sludged oil are not later transferred back into the reconditioned transmission.
(1) Disconnect both cooler lines at radiator.
(2) Dislodge any foreign material at the inlet side of the cooler with a small screwdriver.
(3) Reverse flush the cooler with a combination of mineral spirits and pulsating air under pressure (shop air).
(4) Treat the cooler lines separately and insure they are clear by flowing mineral spirits or automatic trans mission fluid through them.
(5) Remove leftover mineral spirits from cooler and cooler lines by flowing automatic transmission fluid through them.
(6) Cooler flow should now be checked by connecting the cooler tubes and placing the rear cooler tube into a 1 quart container. Overfill the transmission by 1 quart. Watching a clock, start engine (run at curb idle) and run in neutral for exactly 20 seconds. If cooler flow is less than 1 quart in 20 seconds, replace the radiator or have the radiator bottom cooler professionally reconditioned.
Manual Linkage
Normal operation of the neutral safety switch provides a quick check to confirm proper manual linkage adjustment.
Move the selector lever slowly upward until it clicks into the "P" Park notch in the selector gate. If the starter will operate the "P" position is correct.
After checking "P" position move the selector slowly toward "N" Neutral position until the lever drops at the end of the "N" stop in the selector gate. If the starter will also operate at this point the manual linkage is properly adjusted. If adjustment is required, refer to "Gearshift Linkage Adjustment" in "Maintenance and Adjustments".
Throttle Linkage
The throttle rod adjustment is very important to proper transmission operation. This adjustment positions a valve which controls shift speed, shift quality and part throttle downshift sensitivity. If the setting is too short, early shifts and slippage between shifts may occur. If the setting is too long, shifts may be delayed and part throttle downshifts may be very sensitive. Refer to "Throttle Rod Adjustment" in "Maintenance and Adjustments".
Road Test
Prior to performing a road test, be certain that the fluid level and condition, and control linkage adjustments have been checked and approved
.
During the road test the transmission should be operated in each position to check for slipping and any variation in shifting. Note whether the shifts are harsh or spongy and check the speeds where the upshifts and downshifts occur. Approximate shift speeds for the various modes of operation are shown in the "Automatic Shift Speeds and Governor Pressure" chart. Observe closely for slipping or engine speed flare-up. Slipping or flare-up in any gear usually indicates clutch, band, or overrunning clutch problems. If the condition is far advanced, an overhaul will probably be necessary to restore normal operation.
In most cases, the clutch or band that is slipping can be determined by noting the transmission operation in all selector positions and by comparing which internal units are applied in those positions. The "Elements in Use Chart" provides a basis for road test analysis.
By observing that the rear clutch is applied in both the "D" first gear and "1" first gear positions, but that the overrunning clutch is applied in "D" first and the low and reverse band is applied in "1" first, if the transmission slips in "D" range first gear but does not slip in "1" first gear, the overrunning clutch must be the unit that is slipping. Similarly, if the transmission slips in any two forward gears, the rear clutch is the slipping unit.
Using the same procedure, the rear clutch and front clutch are applied in "D" third gear. If the transmission slips in third gear, either the front clutch or the rear clutch is slipping. By selecting another gear which does not use one of those units, the unit which is slipping can be determined. If the transmission also slips in reverse, the front clutch is slipping. If the transmission does not slip in reverse, the rear clutch is slipping.
This process of elimination can be used to detect any unit which slips and to confirm proper operation of good units. However, although road test analysis can usually diagnose slipping units, the actual cause of the malfunction usually cannot be decided. Practically any condition can be caused by leaking hydraulic circuits or sticking valves.
Therefore, unless the condition is obvious, like no drive in "D" range first gear only, the transmission should never be disassembled until hydraulic pressure tests have been performed.
An engine tachometer can be used to determine if the lock-up clutch, in the torque converter, is functioning. An instantaneous rise in engine speed of more than 150 rpm at 45 mph (72 km/h) when the throttle is opened just short of kickdown, indicates that the lock-up clutch is slipping more than normal.
HYDRAULIC PRESSURE TESTS
Pressure testing is a very important step in the diagnostic procedure. These tests usually reveal the cause of most transmission problems.
Before performing pressure tests, be certain that fluid level and condition, and control linkage adjustments have been checked and approved. Fluid must be at operating temperature (150 to 200 degrees F.).
Install an engine tachometer, raise vehicle on hoist which allows rear wheels to turn, and position tachometer so it can be read under the vehicle.
Disconnect throttle rod and shift rod from transmission levers so they can be controlled under the vehicle.
Attach 100 psi gauges (C-3292) to ports required for test being conducted. A 300 psi gauge (C-3293) is required for "reverse" pressure test at rear servo. Transmission and Converter Removal
Test port locations are shown in (Figs. 1 and 2
Selector Lever
Fig. 1
Fig. 2
Shift Speed and Governor Pressure Chart
Test One (Selector in "1")
(1) Attach gauges to "line" and "rear servo" ports.
(2) Operate engine at 1000 rpm for test.
(3) Move selector lever on transmission all the way forward ("1" position).
(4) Read pressures on both gauges as throttle lever on transmission is moved from full forward position to full rearward position.
(5) Line pressure should read 54 to 60 psi (372 to 414 kPa) with throttle lever forward and gradually increase, as lever is moved rearward, to 90 to 96 psi (621 to 662 kPa).
(6) Rear servo pressure should read the same as line pressure within 3 psi.
(7) This tests pump output, pressure regulation, and condition of rear clutch and rear servo hydraulic circuits.
Test Two (Selector in "2")
(1) Attach gauge to "line pressure" port and "tee" into rear cooler line fitting to read "lubrication" pressure.
(2) Operate engine at 1000 rpm for test.
(3) Move selector lever on transmission one "detent" rearward from full forward position. This is selector "2" position.
(4) Read pressures on both gauges as throttle lever on transmission is moved from full forward position to full rearward position.
(5) Line pressure should read 54 to 60 psi (372 to 414 kPa) with throttle lever forward and gradually increase, as lever is moved rearward, to 90 to 96 psi (621 to 662 kPa).
(6) Lubrication pressure should be 5 to 15 psi (34 to 103 kPa) with lever forward and 10 to 30 psi (68 to 204 kPa) with lever rearward.
(7) This tests pump output, pressure regulation, and condition of rear clutch and lubrication hydraulic circuits.
Test Three (Selector in "D")
(1) Attach gauges to "line" and "front servo release" ports
(2) Operate engine at 1600 rpm for test.
(3) Move selector lever on transmission two "detents" rearward from full forward position. This is selector "D" position.
(4) Read pressures on both gauges as throttle lever on transmission is moved from full forward position to full rearward position.
(5) Line pressure should read54 to 60 psi (372 to 414 kPa) with throttle lever forward and gradually increase, as lever is moved rearward.
(6) Front servo release is pressurized only in direct drive and should be same as line pressure within 3 psi (21 kPa), up to downshift point.
(7) This tests pump output, pressure regulation, and condition of rear clutch, front clutch, and lock-up clutch hydraulic circuits.
Test four (Selector in Reverse)
(1) Attach 300 psi gauge to "rear servo apply" port.
(2) Operate engine at 1600 rpm for test.
(3) Move selector lever on transmission four "detents" rearward from full forward position. This is selector "R" position.
(4) Rear servo pressure should read 145 to 175 psi with throttle lever forward and increase gradually to 230-280 psi as throttle lever is moved rearward.
(5) This tests pump output, pressure regulation, and condition of front clutch and rear servo hydraulic circuits.
(6) Move selector lever on transmission to "D" position to check that rear servo pressure drops to zero.
(7) This tests for leakage into rear servo, due to case porosity, which can cause reverse band burn out.
Test Result Indications
(1) If proper line pressure, minimum to maximum,is found in anyone test, the pump and pressure regulator are working properly.
(2) Low pressure in "D, 1, and 2" but correct pressure in "R" indicates rear clutch circuit leakage.
(3) Low pressure in "D and R" but correct pressure in "1" indicates front clutch circuit leakage.
(4) Low pressure in "R and I" but correct pressure in "2" indicates rear servo circuit leakage.
(5) Low line pressure in all positions indicates a defective pump, a clogged filter, or a stuck pressure regulator valve.
Governor Pressure
Test only if transmission shifts at wrong vehicle speeds when throttle rod is correctly adjusted.
(1) Connect a 0-100 psi pressure gauge, to governor pressure take-off point, located at lower left side of extension near the mounting flange (Fig. 2).
(2) Operate transmission in third gear to read pressures and compare speeds shown in chart.
If governor pressures are incorrect at the given vehicle speeds, the governor valve and/or weights are probably sticking. The governor pressure should respond smoothly to changes in mph and should return to 0 to 1-1/2 psi (10 kPa) when vehicle is stopped. High pressure at stand still (above 2 psi) will prevent the transmission from downshifting.
Throttle Pressure
No gauge port is provided for throttle pressure. Incorrect throttle pressure should only be suspected if part throttle upshift speeds are either delayed or occur too early in relation to vehicle speeds. Engine runaway on either upshifts or downshifts can also be an indicator of incorrect (low) throttle pressure setting.
In no case should throttle pressure be adjusted until the transmission throttle linkage adjustment has been verified to be correct.
CONVERTER STALL TEST
WARNING: During test let no one stand in front of vehicle.
The stall test consists of determining the engine speed obtained at full throttle in "D" position only. This test checks the torque converter stator clutch operation, and the holding ability of the transmission clutches. The transmission oil level should be checked and the engine brought to normal operating temperature before stall operation. Both the parking and service brakes must be fully applied and front wheels blocked while making this test.
Do not hold the throttle open any longer than is necessary to obtain a maximum engine speed reading, and never longer than five seconds at a time. If more than one stall check is required, operate the engine at approximately 1,000 rpm in neutral for 2 seconds to cool the transmission fluid between runs. If engine speed exceeds the maximum limits shown, release the accelerator immediately since transmission clutch slippage is indicated.
Stall Speed Above Specification
If stall speed exceeds the maximum specified in chart by more than 200 rpm, transmission clutch slippage is indicated. Follow the transmission oil pressure and air pressure checks outlined in this section to determine the cause of slippage.
Stall Speed Below Specification
Low stall speeds, with a properly tuned engine, indicate torque converter stator clutch problems. A road test will be necessary to identify the exact problem. If stall speeds are 250-350 rpm below specification, and the vehicle operates properly at highway speeds, but has poor through-gear acceleration, the stator overrunning clutch is slipping (lock-up and non lockup torque converters).
If stall speed and acceleration are normal, but abnormally high throttle opening is required to maintain highway speeds, the stator clutch has seized (non lock-up torque converter only). Both of these stator defects require replacement of the torque converter. Noise A whining or siren-like noise due to fluid flow is normal during stall operation with some converters; however, loud metallic noises from loose parts or interference within the assembly indicate a defective torque converter. To confirm that the noise originates within the converter, operate the vehicle at light throttle in "D" and "N" on a hoist and listen under the transmission bell housing.
CLUTCH AND SERVO AIR PRESSURE TESTS
A "NO DRIVE" condition might exist even with correct fluid pressure, because of inoperative clutches or bands. The inoperative units, clutches, bands, and servos can be located through a series of tests by substituting air pressure for fluid pressure (Fig. 3).
The front and rear clutches, kickdown servo, and low-reverse servo may be tested by applying air pressure to their respective passages after the valve body assembly has been removed. To make air pressure tests, proceed as follows: Compressed air supply must be free of all dirt or moisture. Use a pressure of 30 psi.
Front Clutch
Apply air pressure to front clutch "apply" passage and listen for a dull "thud" which indicates that front clutch is operating. Hold air pressure on for a few seconds and inspect system for excessive oil leaks.
Rear Clutch
Apply air pressure to rear clutch "apply" passage and listen for a dull "thud" which indicates that rear clutch is operating. Also inspect for excessive oil leaks. If a dull "thud" cannot be heard in the clutches, place finger tips on clutch housing and again apply air pressure. Movement of piston can be felt as the clutch is applied.
Kickdown Servo (Front)
Direct air pressure into front servo "apply" passage. Operation of servo is indicated by a tightening of front band. Spring tension on servo piston should release the band.
Low and Reverse Servo (Rear)
Direct air pressure into rear servo "apply" passage. Operation of servo is indicated by a tightening of rear band. Spring tension on servo piston should release the band. If clutches and servos operate properly, no upshift or erratic shift conditions indicate that malfunctions exist in the valve body.
FLUID LEAKAGE-TRANSMISSION CONVERTER HOUSING AREA
(1) Check for Source of Leakage. Since fluid leakage at or around the converter area may originate from an engine oil leak, the area should be examined closely. Factory fill fluid is dyed red and, therefore, can be distinguished from engine oil.
(2) Prior to removing the transmission, perform the following checks: When leakage is determined to originate from the transmission, check fluid level prior to removal of the transmission and torque converter. High oil level can result in oil leakage out the vent located at the top of the front pump housing. If the fluid level is high, adjust to proper level. After performing this operation, re-check for leakage. If a leak persists, perform the following operation on the vehicle to determine whether it is the converter or transmission that is leaking.
Leakage Test Probe
(1) Remove converter housing dust shield.
(2) Position vehicle with front lower than back so that accumulated fluid in converter housing will drain out. Wipe inside of converter housing as dry as possible. A solvent spray followed by compressed air drying is recommended.
(3) Fabricate and fasten test probe (Fig. 4) securely to convenient dust shield bolt hole. Make certain torque converter is cleared by test probe. Tool must be clean and dry.
(4) Run engine at approximately 2,500 rpm with transmission in neutral, for about 2 minutes. Transmission must be at operating temperature.
(5) Stop engine and carefully remove tool.
(6) If upper surface of test probe is dry, there is no converter leak. A path of fluid across probe indicates a converter leak. Oil leaking under the probe is coming from the transmission converter area (Fig. 5).
(7) Remove transmission and torque converter assembly from vehicle for further investigation. The fluid should be drained from the transmission. Reinstall oil pan (with new gasket) at specified torque. Possible sources of transmission torque converter area fluid leakage shown in (Fig. 5) are:
(1) Torque Converter Hub Seal.
(a) Seal lip cut, check converter hub finish.
(b) Bushing moved and/or worn.
(c) Oil return hole in front pump housing plugged or omitted.
(d) Seal worn out (high mileage vehicles).
(2) Fluid leakage at the outside diameter from pump housing "0" ring seal.
(3) Fluid leakage at the front pump to case bolts.
(4) Fluid leakage due to case or front pump housing porosity.
(5) Oil leakage out the vent.
(6) Kickdown lever shaft access plug.
Converter Leakage Fig. 6
Possible sources of converter leakage are:
(a) Torque converter weld leaks at the outside diameter (peripheral) weld.
(b) Torque converter hub weld.
Air Pressure Test of Transmission
Fig. 7-8
Fig. 9
Fig. 10
Fig. 11
Fabricate equipment needed for test as shown in (Figs. 7 through 11). The transmission should be prepared for pressure test as follows after removal of the torque converter:
(1) Install filler tube bore plug, propeller shaft yoke (tie in with cord or wire), flared tube fitting cap (on front cooler line fitting), and a short piece of tubing, flared at one end, on the rear cooler line fitting (Fig. 12 and 13).
(2) Remove necessary front pump housing bolts. Install vent plug (rubber stopper), and vent plug retainer preferably using longer bolts than those removed.
(3) With rotary motion, install converter hub seal cup over input shaft, and through the converter hub seal until the cup bottoms against the pump rotor lugs. Secure with cup retainer strap (Fig. 9), using converter housing to engine block retaining bolts.
(4) Attach and clamp hose from nozzle of Tool C-4080 to tubing which is on the rear cooler line fitting (Fig. 13).
(5) Pressurize the transmission using Tool C-4080 until the pressure gauge reads 8 psi. Position transmission so that pump housing and case front may be covered with soapy solution or water. Leaks are sometimes caused by porosity in the case or pump housing. CAUTION: Do not, under any circumstances, pressurize a transmission to more than 10 psi. If a leak source is located, that part and all associated seals and gaskets should be replaced with new parts.