Ford Repair: 1989 Mercury Grand Marquis(crown Vic), mercury grand marquis, 1989 mercury grand marquis

Question
HI,
 I have a 1989 Grand Marquis, 302 with OD tranny. My original problem was the trany ran great except it would not shift into a lower gear when you punch it. I took it to a tran repair shop and they opened the pan and found a few metal shavings and an original plug that was part of the manufacture process. They said the tran was in need of a complete rebuild ($1800).  I almost went with it but decided to look a little more myself. I found that the grommet on the throttle body was gone and the assy was just hanging connected to nothing(wondering whey they did not find this?). I fixed that. Now it works fine when you punch it. The problem now is that when it shifts to overdrive it does not want to engage.(slips) In drive it seems to be ok. Problem is worse in OD. I had the tran flushed thinking that they had contaminated the fluid when they dropped the pan. The flush and new fluid did not improve the problem. The car has 120,000 but is in excellent condition and NEVER driven hard. It was my Father in  Laws car. His Baby. Is it posible that they did something else to the tran (except missing the loose throttle body) Is it possible that I need to adjust the Throttle if so which direction.Please help.

Thanks,
Mike Woehrle

Answer
Hello and thanks for the question...I'll try to help.
I can't see any shop "doing" anything other than being a poor repair place. I don't think they would knowingly do something to damage the transmission, or at least I hope not.
What I would suggest to you is that you get a transmission pressure gauge and hook it up to the test port and take some readings with the transmission warmed up, in park, reverse, neutral, OD, drive and 1.
What I try to aim for in throttle valve adjustment is when in drive, to have the gauge read at 35-40 psi.
Hope this helps,
Erik