I appreciate all the help, folks!

That's the first thing I did on my '94 mustang, was a fluid & filter & Mercon V.

NO difference AT ALL.

Then I added the Dr. Tranny stuff and it made a huge improvement. I added a 2nd dose and it's almost completely gone.

Yeah it doesn't fill me with a lot of hope for the future either, but it's still working and WAY better than it was.

How does this Dr. Tranny lubeguard work? Just what does it do to stop the shutter?

Mercon V is known as an HFM fluid...Highly Friction Modified. It was developed by Ford primarily to address the shudder issue caused by a phenomenon called "stiction" in the torque converter clutch. Stiction is where the clutch material alternately slips then grabs, producing the "rumble strip" feeling and is caused by a breakdown of the fluid/friction material interface. Ford's solution was to increase the amount of friction modifiers in the fluid. These are the same friction modifiers used in gear lube for limited-slip differentials. It's one of the primary improvements over plain Mercon.

Dr. Tranny is a concentrated dose of FM.

A few fragments of info in this clip...

Interesting,thanks. I just like to know how and why things work. Thanks again.

Just thought I'd add that I went and bought the Dr. Tranny stuff so I could form my own opinion.

I know nothing about the history of my fluid and I'm not changing it until spring - if then. It did appear decent on the stick, though. Anyway, I bought 2 tubes of DT, dumped one in and went for a drive. The shudder I'd noticed over the past few months could not be felt anywhere, and although I tried, I could no duplicate it even once.

Also, previously when going up hill the transmission shift was kinda hard and noticeable. Now it's incredibly smooth. The kick-in feels almost effortless.

Just my observations, judge for yourself.

I have put it in, and have noticed a difference already, but it's been several days now. However, I did notes definite improvement almost right away.

I emailed the company with some questions about the product and the representative said that it was OK to add 2 tubes if you don't experience the results you desire, but to never add any more than 2 tubes. I bought 2 but just used 1.

x200, definitely sounds like a misfire. 4.6s can be really soft with misfires, feels more like a trans issue but happens under different circumstances. But the fact that its "shuddering" when accelerating under load (ie: accelerating without downshifting) sounds much more like a misfire from a weak coil/plug. [/quote]

man, you guys are dead on with this. i had a bad (no. 7) plug wire a few months ago. under hiway cruise conditions, the car would shudder badly. i was scared that it was the tranny because it felt SO much like it was slipping and grabbing. the CEL came on and i read the code. i did a plug and wire change and all gone. the correct word for these misfires is "soft". well put.

just in the last few days it has come back. but i think that the intake finally let go at the rear water hose fitting. i think it is leakint into the plug hole and shorting out the plug. time to change the intake.