Hmmm. Not wishing to be too pessimistic but, as a worst case scenario (& hopefully it will turn out that there’s a simpler and less costly electrical/electronic cause), you may have had an A-clutch drum failure. These were all the rage with the 5HP24 until the end of 2000, when a strengthened A-clutch drum was introduced, and clearly your 2002 vehicle should have the upgraded drum. However, the later drums do still occasionally fail.

The A-clutch is used in 1st, 2nd, 3rd and 4th gears so the control system immediately selects 5th gear (B-clutch & D-brake) if it detects unexpected slip across the A-clutch. Reverse uses the C-clutch & F-brake, so is unaffected by this failure.

Small parts of the broken drum would most likely end up in the sump, stuck to the magnets, if this were the cause.







We really need to determine if your transmission is failing safe to 4th gear or to 5th gear.

Phil