The oil level is low.

Add oil in order to acquire the proper oil level. Refer to Transmission Fluid Check .

Restricted or leaking oil cooler lines.

1. Check the lines for kinks or leaks.
2. Reroute or replace the lines as necessary. Refer to Transmission Oil Cooler Line Replacement .

The transmission is excessively leaking oil internally.

Check other pressures. Check valve body mounting bolts.

Refer to the applicable Allison Transmission Manual.