'88 Grand Marquis - AOD

Has the standard issue 5L V-8 and AOD. This is my parents car and has about 40k on it. If I have the story right, it first lost passing gear. Linkage
ends are OK and tight. It stopped shifting and now stays in first gear. Forward engagement is harsh and sudden in any forward position. Reverse engagement is normal. I can detect no slippage and the fluid seems OK and doesn't smell bad. There seem to be no shops in their town that do automatic transmission work and no Ford dealer for 50 miles.
I suspect the valve body is geezed but I am 200 miles away. I am sure I can obtain a valve body from a recycling yard, rebuild it, and put it in but I'd like to pick the brains of the group to see if it looks like I am headed the right direction. I have read that the AOD's of this vintage also had some accumulator problems. Since I have to travel 3 hours to get to it - I'd like to have as many options covered as possible before I get there.
The town has an AutoZone and a NAPA. I think the local AutoPro dealer is still in business, too, but I live in Dayton, OH - car parts stores and recyclers are everywhere over here.
Please give advise, suggestions, or just commisserate. I appreciate them all.
Thanks!
Paul E - Dayton
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I had a similar problem (89 Grand Marquis) although my symptoms were not quite as severe. The Problem was the Throttle Valve Grommet which I obtained from the dealer and replaced myself (Thanks to people's help in this newsgroup) This website also helped me replace the TV grommet and tune it. [BLOCK TYPE-TV CABLE ADJUSTMENT] : http://tnmotorsports.com/aod.htm
Pooya

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Thanks folks. I figured all of the symptoms pointed to the kickdown linkage but I have checked the kickdown linkage at both ends. The top grommet was replaced about a year before trouble began. I do not think the car was driven with a bad grommet because I broke it while doing a throttle body cleaning and fixed it before I allowed it to go anywhere.
The tranny lever moves as it should and seems tight. I guess I will have to go over and drop the pan before I can figure out what happened. This will be a backyard job - there is no garage. I can put it up on ramps and do some exploration. My folks aren't anxious to drive right now so it can sit there for a while. As long as I put the pan back on before I crawl out from under it everything should just sit safely.
I was trying to work it out before I got into it but it's a bit too strange.
I appreciate the suggestions... any more?
Thanks - Paul

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I'm a week late but perhaps you'll see it. Are you saying the tranny problem began with not downshifting? There's no such thing as a 'passing gear', that term merely refers to a forced downshift from a higher to a lower gear. The AOD will downshift to 1st gear under 35 mph when the throttle is floor boarded from a higher gear, over 35 and under 55 will shift down to second gear. Above 55 the downshift will be 4th to third. To me it sounds like a throttle valve (TV) positioning problem. AOD's are very sensitive to this.

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