Does anyone know what my mityvac reading should be on the transmission line from the blue vacuum amplifier on my 85TDT. I'm getting readings of 5-7.5 The trans is downshifting extremely hard. I'm not sure if I have a leak or my pump is on its way out. Do pumps slowly degenerate or do they all of a sudden quit?

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85 300TDT 456,000 orig. miles