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Discussion Starter #1 (Edited)
I did the swap to Mercon V (including TC) a good while back to cure the original shudder, as per the TSB. That fixed it for a while. Then micro shudder (more subdued than the original) began and when I called a tranny shop, the owner was reluctant to do another fluid change (I couldn't do it myself for various reasons at the time) and instead recommended I try a friction modifier. That helped for a while.

The shudder eventually returned and became more pronounced in short order. I noticed the fluid level was a tad low, so I topped it off and NOW I'm getting random tranny hop (pulsing).

Shift points are normal, there doesn't seem to be any lag or other anomalies, it just pulsates (intermittent slip) after a gear has engaged (yes, shudder during engagement and pulsing the rest of the time).
It occurs regardless of speed or gear. It's also inconsistent with acceleration -- sometimes I can punch it and there will be no pulsing; other times there will be a major effect; same goes for casual acceleration.
If I back off on the accelerator, the pulsations stop and often don't return when I again apply pedal (gingerly).

It usually, but not always, occurs after the tranny has reached nominal operating temp.

Is this likely a case of the Castrol Mercon V breaking down, losing its viscosity already or am I looking at more involved problem$ like friction plates? I suspect the fluid, but I suppose the friction plates could be acting up only after they warm up -- but wouldn't they be more likely to produce prolonged and consistent slippage?
Also, I did not perform a flush at the TSB change, I just drained the tranny (unplugged TC and yanked the pan). I know if there's old non-V fluid left it can cause shudder to return, but this more severe pulsing effect? I did not pull the VB, either; would enough fluid remain in the VB to lead to this?

I've purchased enough Motorcraft Mercon V for a system refill and a new Fram filter, but I would hate to see that $75+ in fluid gone to waste if it won't fix me up.
So, would you recommend the fluid/filter change or should I hold the material in my personal inventory and head straight to a tranny $hop instead for a thorough flush and/or who knows what else?

FWIW, I've done an overhaul before (on a different make), and I'm a consumer electronics tech for 25+ years, so I'm comfortable around servo-mechanisms.
However, this is my DD and it's my only transportation ATM; I can't be out a car for the length of time it'd take me to do major work on it, if I could even manage to safely drop the whole tranny on my own -- I also don't have a flush machine.

edit: forgot to mention this tranny has 83,800 miles on it..
 

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The shudder is coming from the Torque Converter Clutch when its slipping during lock-up just like the old E4OD's in the earlier ford trucks which can be caused by low lock-up fluid pressure or worn Tor Con Clutch linings So either rebuild the trans and get a new/rebuilt Tor Con or gamble with just replacing the Tor Con but there maybe "flakes" of clutch lining in your trans mainly in the valve body area . I would search the forums or contact Dirty Dog. Hope this helps
 

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Discussion Starter #3
Pardon the delayed response.

Prior to posting here, I searched the forums and read hundreds of posts. The threads were discussing the usual, garden-variety Mercon-related shudder or other symptoms which don't exactly match mine.

Anyway, an update:
Having noticed the fluid level was a little above normal, I used a hand vac pump w/cup to pull out about 1.5-2 quarts via dipstick and refilled to correct level using some Castrol Mercon V that I had remaining from the TSB change.
I checked it hot after 20 miles driving, topped up to level, then test drove again. This modest amount of new fluid made a noticeable difference.
I suspect the Castrol fluid is broken down and a complete refill might help a lot more, if not cure it.
I may have gotten my hopes up for nothing, but it's looking like the fluid is at least a huge part of the problem.
 

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Discussion Starter #4
Btw, can anyone tell me how much fluid is left in the valve body after you drain the TC and drop the pan?
A quart? An ounce?
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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You'll get roughly 6 quarts from the TC and another 2-3 from dropping the pan. Plan on 8-10 fresh quarts if you don't drop the VB or cooler/lines.
 

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Discussion Starter #7
Wow! Considering the capacity is spec'd at 13.9 quarts, if you guys are right, nearly 4 quarts stays in the VB and cooler! That's way more than I expected.
 

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Maybe 5 quarts in the TC and another 5 if you drop the pan .. when you drop the valve body, the TC drains back if there is any fluid remaining .. I usually get up to 12 quarts dropping the VB and draining the TC.
 
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