A/T - Pump Damage After Overhaul
January, 1994Technical Bulletin # 203
^ Transmission: A4LD
^ Subject: Pump damage
^ Application: Ford, Merkur, Mazda
After overhaul, you may experience a problem which results in the pump gears being welded to the pump plate. This problem can occur during start-up immediately after overhaul, or may happen when the transmission reaches full operating temperature such as during a lengthy road test.
The most common problem is a warped bellhousing in the area around the bushing bore. If the bellhousing is warped, there may be no pump gear to face clearance when the pump is bolted down. With extreme warpage there may even be preload against the face of the gears. This causes excessive friction resulting in the gears welding to the plate.
To check for warpage, place a suitable straightedge across the bellhousing as shown (Figure 1). See if the straightedge has a gap at the outside edge (Figure 2). Ideally the bellhousing should be totally flat.
If it is warped it will be necessary to have the housing machined or replaced.
Note:
Make sure the pump bolts don't bottom out after having the bellhousing machined.
Note:
Replacement pump gears that are too thick for the depth of the pump bore could also cause this problem. If you replace the pump gears, be sure to check the gear to face clearance before assembling the pump. The clearance should be .0075"-.0025".