Join Date: Jul 2011
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First let me say forgive me for my terminology I'm new to Powerstrokes and Fords, so please correct me if necessary. However I am not new to fixing broken stuff, so I'm willing to learn.
I'm having a very similar problem in my girlfriend's truck. It feels like some kind of driveline vibration. I'd say the best way to describe it is like driving on rumble strips, but only with enough throttle to sustain a speed over 40mph. Let off the throttle, coast, or go wide open it's not as bad, give it "sustain speed" throttle and it's horrible. Put it in neutral at speed and it's not as bad. Free revving the motor at speed in neutral does not affect it. It almost has a binding feeling. I pulled the front driveshaft as well to eliminate some factors, but it did nothing.
I checked and changed the diff fluid and found some gear glitter and a few small nail clipping size shavings. Very thin. Not sure if that's enough to be alarmed about but I figured I'd note that. From my research her 03 F350 SRW has the sterling 10.5", correct? I'll post pictures of my findings.
Today I'm going to check the fluid in the transfer case, I just rebuilt 2 transfer cases in my Dodge, so pulling and rebuilding another one won't bother me. Putting it in 4HI yielded the same vibration, 4L0 I got nothing, but didn't go over 40mph in 4LO.
I was also thinking TCC [torque converter clutch] maybe a possibility, does anyone know how to force lock or unlock of the TCC to eliminate that as well? On dodges we just ground a wire in the PCM.
I also noticed the 7.3L "injection clicking" stops when you let off the throttle, but it starts again to sustain speed. Could that have any affect on the vibration? I'm wanting to rule this out since in neutral and free revs the problem isn't as bad. Not sure if the motor being put under load could change anything.
I'm committed to figuring this out, so let's start knocking down the possibilities.
Any guides to sterling rear ends on here?