12-06-2002, 05:36 AM
There are eight major mechanical "clutch" components in the 91-94 A4LD. There are three bands (overdrive, intermediate & low/reverse), three clutches (overdrive, reverse/high,& forward), and two one way clutches (overdrive & rear). The following simple tests can begin to isolate the problem. Prior to performing these tests, check for correct transmission fluid levels when the engine is warm. Look for discolored fluid with a burnt odor.
1. Does the vehicle move with the shift lever in reverse? This tests the overdrive clutch, overdrive one way clutch, reverse/high clutch, and the low/reverse band. This is a primary a test for Low/Reverse band.
2. Does the vehicle move with the shift lever in manual low (1) position. This tests the overdrive clutch, overdrive one way clutch, forward clutch, low reverse band, and the rear one way clutch. This is a primary a test for Forward clutch.
3. Does the vehicle move with the shift lever in manual second (2). This tests the overdrive clutch, overdrive one way clutch, intermediate band, and the forward clutch. This is a primary a test for Intermediate band.
4. Find a fairly steep hill and point the vehicle in a downward direction. Place the vehicle in manual low(1). Remove your foot from the brake and do not touch the gas pedal. Allow the vehicle to accelerate on it's own. There should be significant engine braking as indicated by the tach going to 2-3K. This is the primary a test for Low/Reverse band servo leakage.
5. Find a level section of highway and travel at a steady speed of 55-60. Observe the reading on the tach. Now, gently apply the brake with your left foot. You only want to apply enough pressure to operate the brake light. The rpm on the tach should increase 300-400 rpm. This will disengage the torque converter clutch. If the rpm does not increase, the torque converter was not engaged prior to applying the brake. This likely indicates a valve body or TCC solenoid problem. If you see a rpm the TCC is working.
6. At highway speeds, the tach is where it always used to be. If a lot higher, then this indicates a problem in the overdrive section of the transmission. This tests the overdrive band, reverse/high clutch, and the forward clutch. If tach rpm is normal then the overdrive is still working.
7. The transmission has a later shift point than it used to have in drive out of both first and second. This indicates a problem with the vacuum modulator. Check the vacuum hose going to the modulator at the vacuum tree for signs of transmission fluid.
8. The transmission has a later shift point than it used to have in drive only out of first. This indicates a problem with the speed governor.
9. When the vehicle is cold, the transmission is slow to go into forward or reverse when you first try to remove it. This is likely a clogged filter and very old fluid. This is a precursor to other problems. The pan should be dropped and inspected for debris. This is only a partial list of diagnostics but it will identify many problem areas. The ATSG manual has 15 pages of diagnostics.
