If your engine RPM is reasonable (ie around 3000/3500@ 60 MPH) maybe what needs work is your exhaust system?
Another thought to see how many transmission gears you have access to. Put gear selector in LOW. speedup to 20MPH then shift to drive (quickly after it upshifts pull gear selector BACK to LOW) this locks the transmission into second gear. Accelerate to 35MPH and then put gear selector back into drive. That should access third gear. This WILL NOT HARM ANYTHING. Tell us what happens. Pete

I was mistaken and gave false info.

The MERC-O-MATIC (medium main case) was introduced in 1951 along with the FORD-O-MATIC (small main case).

Sorry if I caused any confusion.

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Nicely said darrell. In these days of 1500rpm cars we do tend to forget.

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

your not going to hurt your engine.back in the day as they say we drove these things 70 and 80 all day.we forget what they run like when i got my 56 after 40 years i took it down the road and i thought the motor was going to come through the firewall.i cant drive this thing. 2 days later i had the window down stuck the arm out and let her fly.

Here’s a link to getting the rear end ratio. Note the cautions-blocked wheels, jack stands, this is not a bumper jack operation.
It can be difficult to tell the difference from a 3.5 to 3.7, (or a 4:11 to 4:30 whatever) but careful marking will get you real close.

http://www.how-to-build-hotrods.com/gear-ratio.html

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

I’ll suggest first verifying the rear end ratio.  What should be there versus what actually is there after 60+ years may not be the same.  Once you know that for sure, then post both the rear gear ratio and your tire size and someone here on the site can do the calculation to determine a given rpm for a given speed.

Lorena, Texas (South of Waco)

Merc. Matic blues! Well I’ve been told by many of you on this site that my 54 takes off in second,then shifts to 3 rd.I guess I thought these cars would run at 70 mph all day and now 55 mph is my limit without ruining my engine. Any thoughts guys?

Actually what you need is the Lincoln/Mercury manual.  It will cover everything from 1951 through 1958 on the Merc-O-Matic and 1955 trough 1958 on the Turbo-Drive.  I have one that I've scanned.  It does have an excellent trouble shooting quite.  

Until you can get the engine RPM from an accurate tach o meter it is just a big guessing game. For reference my 55Tbir ( FOM and 3.31 rear axle ) reads about 3000RPM at 60 MPH. Pete

Read This Again-

"Your transmission style is known as a SINGLE RANGE FORD-O-MATIC and it starts in 2nd gear mainly for fuel usage reasons. It starts in 2nd and goes into 3rd making one think a gear is missing. If you want a 1st gear start, you either pull the selector lever into L or use WOT (wide open throttle) from start."

If you feel two shifts, it is either a FOM or possibly a later COM (or even FMX for that matter). Can you get under the car to find the TRANS ID PLATE?

If the car does reach 3rd (direct) and you are experiencing high RPM, then the rear axle ratio is too low for highway cruising.

Is is possible the car was assembled with a 3/S/OD from the factory and the previous owner installed an AT?

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