Wifley, you could be right. I am not 100% sure about the missfire but I did 3 tests and all pointed to TC O/D lock up problems:
1. While shuddering at 80 km/h, tap the brake and shuddering was gone.
2. While shuddering, pushed in the O/D button (OD off), shudder gone.
3. Take the O/D off, drove all day with no shuddering.

My ex neighbour was a local Ford dealer parts Dept. manger ( he passed away recently) and he introduced me to some honest mechanic as well as the manager of the service dept.

To make the story short, today I went to see this service manager and told him about the tranny shudder problem. He immediately recongised the problem and said the first step is to complete flush the tranny and if problem still presist, then look for low grade missfire. I asked for other maintenance services and he turned down half of them. Don't want me to "waste" the money. That really is a true friend.

I welcome any suggestions and advices. I will update the post when the problem is fixed.

 

I see this a lot with these, the customer complaining about the transmission or TCC shuddering. It is possible for the converter to shudder and changing the fluid usually takes care of it, but.. 90% of the time its the engine, cylinder misfires.

The tests that I see you guys talking about with driving it at using the brake or the shifter to release lock up and "if the problem goes away its the converter" can be misleading.

When the converter is NOT in lock up the converter is driving the trans by "fluid coupling" what that means is fluid is being used to drive the input shaft of the transmission and there is no mechanical or direct connection to the crank. When the converter is in this state engine misses or slight surges are absorbed in the fluid and not transmitted through the trans. When the converter "locks up" the stator inside the converter that drives the input shaft is no longer driven by fluid but by a mechanical connection to the crank by locking the stator to the back cover that is connected to the flywheel and crank, "lock up". Sometimes under heavy acceleration from a stop you can feel the engine surging or missing with the trans out of lock up if you pay close attention.

The best way to figure out if you are dealing with a converter problem or engine miss is by using a scanner that is capable of monitoring engine misfires. Mine can do it in the on board monitor section of the functional tests in the scanner. I would assume that most scanners that are not used professionally may not have this function. Also TCC slip can be monitored on some vehicles, so if its in full lock and the TCC slip is not steady somewhere around 0 rpms you could have a slipping converter. Most noticeable but minor engine misfires will not set a code or the check engine light.

We had a Navigator in the shop yesterday, she said her mechanic told her that the converter was shuddering. I took it out and felt the "shudder" and my scanner told me that on my one road test that cylinder 8 missed 38 times and cylinder 3 missed 12 times. Replaced those two coils and plugs and the shuddering was gone.

I would recommend finding a scanner and someone who knows how to use it and what to look for before doing anything, especially replacing the converter. I cant remember the last time I replaced a converter due to shuddering.

 

my shudder problem seems to differ from all of these, I have an 04' 150, 90k 5.4l

my shudder seems to come from my rear end only when accelerating at a turn from a stop, seems to be worse when the truck and the air temp is colder.

most posts I read pint me to clutch packs in the rear diff. anyone know the cost of replacoing those? and I see a lot of people changing the fluid or adding the limited slip stuff but with so many mixed reviews im not sure what to do. I suppose I should change the fluid first off