Low EPC in Drive, fine in Reverse, Manual 1-2 | Ford Explorer Forums - Serious Explorations

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Low EPC in Drive, fine in Reverse, Manual 1-2


New Member
July 11, 2014
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Year, Model & Trim Level
Ford Ranger
Have a '98 Ford Ranger 4.0 5R55E 4WD. Has a little over 300,000 miles, engine has been replaced but transmission is original as far as I know.

Anyways, lost 4th and 5th gear. 1st, 2nd, and 3rd are fine. Got P0734 and P0735 codes. If you drive it over ~40 MPH or so for a few minutes, eventually the O/D light still start blinking, and 4th/5th will actually come back and engage, presumably because its commanding maximum line pressure.

Reverse for the most part is fine, with a slight delay in engagement.

I've just been driving it in Manual 2nd in the meantime, as my commute doesn't require any highway driving.

I just hooked a pressure gauge up to the EPC port (I would have done mainline, but my line is only rated for 140 PSI). The results of the test were interesting.

EPC Reverse Idle: 60 PSI
EPC Reverse WOT : 120 PSI
EPC Drive Idle : 31 PSI

Now EPC Drive WOT is where things get interesting, when you first floor it, the pressure will build to about 60 PSI by around 2500-3000 RPM, however as the RPMs climb past that point, EPC actually starts to fall to around 45-50 PSI.

I also noticed that when you engage reverse at idle, you will feel it engage, but the EPC will remain at ~30 PSI for roughly 1.5-2 seconds, then you will feel a pulse in the line and pressure will suddenly jump to 60-65 PSI.

Any ideas what is up with this thing?