Stutter/shudder at WOT kickdown: transmission or engine ? Diff chattter ?

me2 · May 21, 2014

2008 F350 6.4 5R110. Totally stock, 160K.

It cruises fine at 65MPH. Sometimes when I floor it to pass another vehicle it surges and studders like crazy. If I back off the throttle a bit it works fine.

Is this a transmission problem or an engine problem ?

I haven't changed the transmission fluid in 70,000 miles. I'm afraid to. I've heard they have a hard time learning to shift again, triggering a rebuild.

Also, I get a constant "jiggle" from the driveline somewhere. I'm pretty sure its the limit slip in the rear diff catching. I had this problem with my 1999 as well. I think it comes from turning sharp corners while pulling big trailers on pavement. Could this vibration be causing the transmission to have issues shifting ?

Thanks

sootie · May 21, 2014

when is the last time the fuel and air filters were changed?

me2 · May 21, 2014

sootie said:
when is the last time the fuel and air filters were changed?

The air filter is perfectly clean. The suction indicator isn't getting set, at least not when I am in a snow storm.

The fuel filter was replaced about 30,000 miles ago. Its due.

Csilva187 · May 21, 2014

&#55357;&#56883; yikes. Maintenance.

me2 · May 21, 2014

Csilva187 said:
�� yikes. Maintenance.

????

Doodie · May 21, 2014

So, the TC is unlocked at 65 mph or locked?

me2 · May 21, 2014

Doodie said:
So, the TC is unlocked at 65 mph or locked?

I haven't hooked up a scanner, but it seems to be locked like it should be when cruising. I certainly doesn't feel like its slipping and the tach confirms that.

Mark Kovalsky · May 21, 2014

me2 said:
Is this a transmission problem or an engine problem ?

I believe it is an engine problem.

me2 said:
I haven't changed the transmission fluid in 70,000 miles. I'm afraid to. I've heard they have a hard time learning to shift again, triggering a rebuild.

That's a new one that I've not heard before. It's not true.