I've got an 02 f150 4x4, 130K+ miles, limited slip diff.

At speeds between 45 and 65 depending on grade, usually around 1500 RPM, when accelerating from a coast, I get a quick shudder (similar to a washboard.) It is very quick, and is accompanied with a short, small spike in RPM.

Changed the rear diff fluid and added modifier about 200 miles ago, no difference.

Leaning towards the torque converter, solenoid, etc. but not sure where to start first.

Any thoughts or suggestions?

 

do you have the 4r70w or 4r100??

 

4r70w

 

what is the condition of the fluid? when was it changed last? is the engine running correctly, (no low grade misfire). the fluid tends to break down and in the 4r70w unit it will cause a lock-up chatter, i would get it scanned through mode 6 to see if they can see the misfire count if there are not, and to confurm that it is a lockup chatter, and if it is try a fluid and filter change( tc drain if you, still possible for you to have a drain plug on it)

 

I agree. One other thing you can try while you are trying to pinpoint the problem is to get the truck to where this happens and 2 foot drive it. What you do is just barely apply the brake pedal just enough to turn on the brake light but not enough to apply the brake at all. This will unlock the torque converter and if the problem goes away right there then you know it's converter shudder.

From that point if you determine that it is the converter then I would go with changing the fluid to Mercon V. Maybe even a full synthetic version other than any of those super high dollar fluids. IE: Royal Purple, Amsoil, Red Line, etc... Don't waste your money there for this. Keep it simple.

Darrin

 

the same shudder happened to me. change your spark plugs(MotorCraft) and you should be good.

 

I was about to post the same. I learned not too long ago that what I thought was transmission issues was really a miss or detonation. Replaced plugs\COP's and good to go!!