Transmission Bang

[John Ward]

2008 Expedition 119,000 miles. Transmission work fine around town. on highway in overdrive at 40/ 60 MPH if I hit the accelerator pedal lightly to gain speed there is a loud bang before it downshifts and gets up to desired speed. Once at desired speed trans works fine unless it tries to downshift to accommodate an uphill grade. No diagnostic codes/ Any ideas appreciated.

 

[metaldrgn]

It would be helpful if you knew when gear you were downshifting to. Should be 4-3 or 3-2.

 

[deweysmith]

Check your differential support bracket and its bushing. Details here. It can wear out on the other side so it only clunks when engine braking or downshifting.