Pulsing Pulling a Load at 50 MPH, 2,000 RPM in 4th Gear

[skibum13]

Whenever I'm going up hill or pulling a load, my truck pulses back and forth. It almost feels like it's missing, but the engine noise doesn't change and I'm almost positive it's transmission-related. The pulsing feeling is like driving on a bumpy road, but instead of an up-and-down motion, it's a foward-and-backward motion. It pulses fairly quickly; maybe 2 times per second.

It only happens in 4th gear at around 50 mph and 2,000 rpm when I'm going uphill or pulling a load. The bigger the load, the more it pulses.

I think that's when the torque converter is supposed to lockup, but i'm not sure.

I have a POS transmission from Phoenix Hard Parts that supposedly came with a heavy-duty TC, but who knows what I actually have. I only have maybe 5k on the new tranny.

Any ideas what could be causing the pulsing sensation?

[Rick2001]

hmmm I would agree with you that is is tranny related. I just had a similar experience with my truck. I had the very same driveability issue.


It ended up flashing me the OD light. When i scanned the truck the code was for the convertor not locking up. It can be one of these two items. the OD switch on the gear shift selector or chaffed wire at the same. Or your VSS can be acting up. If it is your VSS your speedo shoul dbe acting up also.

It may also be in your shift seleniod pack.Try driveing the truck with the OD locked out. If everything is working fine then I would say it is the switch or wires being chaffed and touching intermittantly.


A new selector with OD switch should be about $50.00 from Ford. It took maybe an hour to change it. That was in the driveway with a flash light. No special tools were needed.

Assuming the switch is the problem I would change the fluid soon after driving it. It will clog the filte if not.