Ford 4R100 / E4OD

Ford's heavy-duty rear-drive four-speed — behind the F-250 and Excursion, the Expedition and the Lincoln Navigator.

It is the truck transmission behind the 7.3 Power Stroke, which is most of its reputation: an enormous number of them are still working, and the aftermarket for them is correspondingly large.

Its characteristic failure is heat, and the specific victim is the torque converter. These were fitted to vehicles that tow at their limit, and a converter that has been cooked contaminates the fluid with the material it sheds — which is why a fluid that looks or smells burnt on one of these is a reason to look at the converter rather than only to change the fluid.

The other recurring item is the electronic pressure control solenoid, whose failure defaults line pressure to maximum: every change lands as a bang and nothing has actually broken. A sudden onset of violently hard shifts is that solenoid until proved otherwise — the same fault, and the same reassurance, as on the 4R70W.

The E4OD is the earlier name for the same transmission. Ford renamed it in 1998 with internal revisions; a part listed for one may or may not fit the other, and the model year decides.