Good afternoon ,
We are working on a 1955 Mercury 292 with Ford o matic three speed transmission .
This is a well maintained automobile with all new ignition , Holley carb , and new edelbrock fuel pump . 
This car was running great untill it suddenly was not able to accelerate the car forward or backward with out full throttle . really not good .
Feels like it went from 200 hp to about 20 hp wide open , like a trans brake ???
All brakes inspected car stops great .
It feels like the exhaust is blocked up big time but the exhaust is a year old and feels fine .Dual exhaust and flowmasters .
No backfiring , no exhaust blockage , compression test at 120 psi , valves adjusted to .019 .Motor appears new inside valve cover .
Static vacuum cranking test pulled a wopping  TEN  inches of vacuum . Starts right up , SOUNDS great .
The owner did do a BURN OUT on concrete right before this girl changed her personality immediately .
We believe we may have failed a converter or a sprag or welded the clutches ????
Any thoughts on this sudden change in behavior are thanked !!!
Happy and safe travels to all. 

What's the condition of the transmission fluid? 

Fluid full and red , have not yet pulled pan in do any other inspection ....yet 

when shifted into drive or reverse it is sure and crisp 

It sounds like bad news-maybe the converter or pump. Noise? 

there is no noise that either of can here , and I think you are correct 

was hoping a member who had this unfortunate experience before could chime in , by I do think this is rare!!!

Amazing what makes them run , amazing what makes them QUIT

Did you ask how many rpm he was turning when he dropped it into low for the burnout? Sounds like something I might have done about 60 years ago.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

not exactly the same , but my buddy has a 56 pontiac with hydromatic ,. after a couple mild panic stops to check for front end pull, to my surprise the tranny would not shift out of low gear no matter what . I looked and looked and thought , we added more fluid to no avail . He said lets take it out and drive the snot out of it , to no avail . Then we stopped he reversed to about 30 mph and stopped , put in gear and it worked fine,, I think the governor in the tranny must have stuck.. Wow what a surprise 

yeah I do not mind breaking a 200 or 2000 or 10000 dollar automobile being reliving the events of yesterday , It is fun! 

I do not get doing a burnout with a 60,000 Mercury Montclair Convertible the minute you roll it off the transport truck ., just not a good idea .

I was not there to see the burnout but he said it was a good burnout , and he would certainly know .

thanks to all 

Thanks for that info on the Pontiac !!!

I blew up the torque converter on a GM 200R4 , behind a Corvette L82 and the results were I had to punish the car just to get the two miles to my driveway , felt the same as the Mercury , bound up like brakes on full . 

Expensive mistake lead by watching reality TV. I had to do the same thing with 55 Slant Pan Hydramatic in the mid 60’s. It would not start in 1st. Good luck. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.