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The reason I ask is that I often get 5HP24s to repair where the transmission behaves normally after starting from cold but then after around 20 minutes (which is how long it takes for the transmission fluid to get up to temperature) the transmission failsafe message appears & the transmission goes into limp-home mode (4th gear + open converter). On cooling down again, normal operation is restored.
This is invariably linked to a seal leakage problem. When the fluid is cold and viscous the leakage is small enough that the pump flow is sufficient to maintain pressure on the particular clutch. Once the fluid warms up and the leakage increases the pump cannot maintain pressure and the clutch slips. The ECU detects the slippage via the two speed sensors and drops into failsafe.
Similarly, if the transmission fails to engage either Reverse (C & F clutch) or Drive (A clutch) at tickover, but then slams the clutch(es) on when the engine revs are increased, this could also indicate that the additional pump flow produced by increasing the engine speed was overcoming a seal leakage problem.
Phil
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03-21-2011, 05:45 PM
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