Trans advice sought

2000 XJ Sport 4wd 4.0 automatic 73k miles.

When accelerating gently from a stop to highway speed, it appears to shift into 2nd normally, then when it shifts to 3rd, the TC seems to lock at the same time, and it seems to be locked when it goes into 4th also. I don't like how it lugs the engine.
If I shift manually or step on it instead of driving like a granny, it's fine, or more fine anyway. If I hold it in 3rd until 55 mph or so, then shift into OD, the TC locks immediately whether I'm accelerating or not. Also, it seems like I have to stand on it to get the TC to unlock.

Last fall I changed all the fluids and being ignorant about such things, observed the ATF+4 sticker on the firewall and did a drop and fill with it. I don't drive my XJ every day so it's hard to tell, but tranny slippage seems to have slightly increased since then, but it could just be the voices in my head.

Should I find a place to do a flush with Dexron 3 or do a couple drop and fills to try to get the +4 out? It could get expensive with synthetic doing drop and fills.

You will hear it both ways here.

To make a short story long: until 2007 Chryco specified quite clearly that Dex III ONLY was to be used in the AW4 transmission--a Japanese transmission designed to work correctly with Dex III. Magically, as of October 16th, 2007 ATF+4 was approved for the AW4:

A/T - ATF + 4 Fluid Usage

NUMBER: 21-014-07

GROUP: Transmission

DATE: October 16, 2007

THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 21-010-06, DATED APRIL
14, 2006, WHICH SHOULD BE REMOVED FROM YOUR FILES. ALL REVISIONS ARE
HIGHLIGHTED WITH **ASTERISKS** AND INCLUDES THE ADDITION OF THE ASIAN WARNER
(AW4) TRANSMISSION AND ADDITIONAL MODELS AND YEARS.


Now, a suspicious person might say that since Chryco stopped using the AW4 so long ago they no longer give a damn about any AW4 problems that might come about from using the WRONG fluid--there were no longer any AW4s carried under warranty.


And as we all know, you can simply put any transmission fluid in any automatic transmission and it will work just fine--right? I mean, if you can use ATF+4 in a transmission built for Dex III after a magic date in 2007, then logic says you could use Type F too! Magic dates are, after all MAGICAL!


Do some research, make up your own mind.


Back to your problem.


Have you adjusted the throttle body pressure cable? Read here: http://naxja.org/forum/showthread.php?t=1015963


Have you tested the TPS?