I've spent the past hour or so researching, so I just want to make sure I have read everything properly.

I have the truck listed below in my sig. Had the tranny fluid changed to Mobil 1 synthetic at 34,000 and installed a shift kit (drain converter). At about 60,000 i pulled the pan and replaced (did not drain torque converter). At 75,000-ish, I took it to Jiffy Lube and had them do a "power flush" on it. Now, at 83,000 miles, the trans started shuddering going into overdrive.

There is plenty of fluid. It's not black, discolored, or any more smelly than normal. So I think it is OK. Is there any way to know without guessing? The tranny fluid is about 1" above the full mark on the dipstick. Is that OK? (Jiffy Lube did that, thanks, guys.)

The torque converter fluid is changed during a "power flush", correct?

After changing tranny fluid, some have had luck with additives. That is what I am about to try (unless I hear otherwise). Heading to get the Lucas stuff now. Any reason not to do this?

After that, the Sonnex valves being changed may help. Am I understanding that properly?

And last resort is some sort of a torque converter issue. How do I tell if its really the TC and not that the sonnex valves will help. Is there an easy way to tell?

Thanks for any help/input.

 

first thing I would co is get rid of that 1" above full mark!! too much fluid in that tranny, maintenace sounds rite on the mark.