91 grand marquis transmission mystery solved

[jjamty]

(please read i know its long winded)

i have owned grand marquis for past 5 years and do all my own repairs under my shade tree. the first i had i ended up wrecking and although still very drivable it was ugly with its crushed front end. about a year later i happened on an identical vehicle and since it was in better shape i decided to keep that one, one problem, the new one had a trans prob that you all have heard described a hundred times.

"every time i go above about 38 or so miles an hour the engine free revs like it is slipping"

ever heard that one?? i had a solution at hand though. the original marquis with its sound transmission. so, on a saturday with help from my wife we swapped the two tranny's and guess what??

same problem! now i am ticked so i think to myself it must be harness going to electrical connections on tranny, the computer isnt getting a signal it needs from there and i am just out of luck.

well as luck would have it i was replacing valve covers and as you know it requires pulling the plennum to get the covers off.
i went to unhook the throttle cables from the carb and lo and behold the secondary or kickdown cable wasnt hooked up.

i finished the repair and connected BOTH cables to carb and it shifted and ran like a champ.evidently the computer detects your accelerator position with that cable as well or something and knows when to shift, i dont know i just know it worked and except for changing a healthy tranny i am happy.

good luck to all

jjamty

[6502dude]

Good solution! Hope you kept the removed transmission as a spare.

I did something similiar, years ago.

I changed transmission in 76 Maverick, in the middle of winter, in an unheated garage, using only jackstands to raise car.

Laying on a cement floor in clothes soaked with transmission fluid during Canadian winter is no fun.

I later found problem vacuum line was cause of shift problems.

I tend to learn from my mistakes (I make many) and now don't make assumptions without doing more diagnoisis up front before starting big projects.