99 F-150 5.4L automatic, 4x4, 3.73 limited slip diff, 125K miles

The truck shudders (almost exactly like driving over a rumble strip) when accelerating at low speeds (0-10mph) with a load (uphill or especially towing uphill).

I am not sure what this could be. At first I wondered torque converter. But upon further research I've heard it could be a coil misfire, limited slip clutch, or the differential slip yoke needing grease (per the TSB 0416).

But upon much searching, I can't find anyone else with the exact same symptoms (shuddering on very low speed accel).

I experience this at no other time than stated above. I don't experience any other symptoms and the computer doesn't show any codes.

 

My old truck would shudder and it was due to a bad torque converter, however it would only do it when changing gears (usually between 3 and 4). I went to O'reilys and bought some "Lubegard Dr. Tranny Instant Shudder Fixx - Tranmission Treatment" and that solved my issue.

That doesn't sound like your issue to me, it sounds like something is out of balance. Possibly your drive shaft isn't balanced right? It's not uncommon for a weight to fall off. Of course this issue would be RPM dependent so before checking that, make sure the ruble is RPM dependent.

 

Thanks Red-Ford. I feel like if it was an imbalance issue, I would feel it at other speeds, and particularly at higher RPMs when it's rotating faster. The issue I'm describing occurs around 1000-2000 RPMs in 1st gear only.

 

MY LINK MIGHT HELP
https://www.f150forum.com/f6/shudder...-joint-247865/

 

Thanks. I did see your thread and just posted there. Sounds like your problem remains unresolved like mine.