I have an 07 lariat 4x4 crew cab with the 5.4 flex. The issue that I am having is when I am driving in traffic, if I accelerate easy and the transmission downshifts, I get this slight rumble that almost feels like I just drove over a rumble strip. It only happens for a brief 1/2 second and then it will shift into the lower sear just fine. But it only happens when I accelerate easy. If I accelerate fast, it downshifts just fine. I don't have any other issues with shifting other than that. Does anyone have any suggestions please.

 

Hi.

May not be the tranny - could be low-grade misfires:

https://www.f150online.com/forums/tr...le-strips.html

More ...

https://www.f150online.com/forums/tr...ghlight=rumble

https://www.f150online.com/forums/20...rumble+misfire

Good luck!
MGD

 

How many miles on it?

Have you ever changed the spark plugs or the tranny fluid?

 

It's got 99k on the truck. I replaced the spark plugs about 10000 miles ago.

 

This sounds like the old torque converter mechanical lockup slipping. This was a common problem on the older 4r70W trannys. I had the problem with my 95 Mark VIII. A transmission fluid change fixed my problem. So, my recommendation is to change the trans fluid if it hasn't been changed recently and don't use any additives.

 

Don't just drop the pan - get a shop to do a complete exchange with a machine - WITHOUT using any flush chemicals.