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By Threat51 - 11 Years Ago
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Hey guys I have a 1956 mercury 312 eng didn't think my tranny was going in to high gear hears what I got used tack and gps for speed at 55! I was at 3000 rpm .At lower speed was watching tack no fluctuation in rpms thinking its in second ? Need help .
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By Hoosier Hurricane - 11 Years Ago
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If you can give us the actual tire diameter and the rear axle ratio, we can calculate what rpm should be at a given speed.
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By Pete 55Tbird - 11 Years Ago
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If you are really going 55 MPH and your tack is reading right you are not in second gear. Aside from that it is hard to figure out what you are asking. Can you spend more time explaining your issue. Pete
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By oldave57 - 11 Years Ago
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I believe you are correct that 3000 RPM is too high for 55 MPH, but it would be helpful to know your exact tire size and axle ratio. I have made some assumptions based on the 56 Ford axle ratios in my Fordomatic manual and based on an approximate tire size of a 6.70 X 15 tire (the 56 Fords still had 15 inch tires).
At 55 MPH, you are traveling 4840 feet per minute. If your 6.70 X 15 tire has a 27.50 diameter, your wheel travels 7.199 feet per revolution. If you divide 4840 by 7.199, you get 672.3 RPM for the tire. If your axle ratio is 3.22:1, the driveshaft (and engine in high gear) would be turning at 2164 RPM. One of the tables that I have shows that second gear has a ratio of 1.47:1, so the RPM at 55 MPH in second gear would be 3182 RPM, so that is fairly close to what you measured. Of course, these calculations are approximate, but I believe that 3000 is too high for the engine to be in high gear (3rd gear) in the Fordomatic.
When you are driving the car, you should be able to tell when the transmission shifts from 2nd to 3rd, even if it is at a fairly low speed. Sometimes it is hard to tell when the shift occurs, but it should be noticeable and if the shift never happens, you are probably staying in second gear at road speed.
Hope this helps. Good luck with your diagnosis.
Dave
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By Threat51 - 11 Years Ago
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Will get tire size tommrow. I also adjusted the linkage as the manual said made no difference in the rpms still 3000 .good down shift if you put it in low gear also good up shift when
you put it in drive just not a third gear up shift I don't be leave.used my gps for accurate speed.
Some one suggested pull the govener ? Car is not a overdrive tranny.Running out of ideas lol
Thanks
Bob
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By Threat51 - 11 Years Ago
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Pete what gear would I be in?
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By steinauge - 11 Years Ago
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I hate to belabor the obvious but is the rear end original to the car? I was thinking of someone somewhere having installed one of the 4.10 (or thereabout) overdrive gearsets??
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By Threat51 - 11 Years Ago
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As far as I no its the original rear end .
The tires are 215-75-15
Manual says the gears are for the car 3.15 or optional 3.54
The rest of the car is original as far as I can see.
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By Threat51 - 11 Years Ago
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Dave you are on with the rpms that's about what I am at.
Bob
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By charliemccraney - 11 Years Ago
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Threat51 (8/27/2014)
Manual says the gears are for the car 3.15 or optional 3.54
The rest of the car is original as far as I can see.
The car is 58 years old. It can have anything installed and look original from the outside at this point. To get any concrete answer, you need to determine, positively, the gear ratio.
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By Daniel Jessup - 11 Years Ago
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With the original Fordomatic, if you place it in Dr, and then pull off under normal driving conditions (in other words, don't "tromp" it lol), you should only have ONE shift from second to third. That is the way to tell very quickly whether or not you are really in 3rd gear. Starting in Lo, and then shifting to Dr will take you from 1st and then to 2nd. Leaving the car in drive and continuing to accelerate will eventually put you in 3rd gear.
I know we have been all over the place here, but all of the tire calculations are not worth a hill of beans unless you have shifted into 3rd gear. The original Fordomatics took OFF IN SECOND GEAR from a stop and in the Dr position on the selector.
I believe you are in 3rd gear at 3000 rpm at 55 mph. Have you had a shift when take off in Dr? If you have then YOU ARE IN 3RD GEAR, if not then you ARE ONLY IN SECOND.
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By Threat51 - 11 Years Ago
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I have not felt a shift and the tack never drops off at all you would think that there would be a little fluctuation of the shift right ?
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By Threat51 - 11 Years Ago
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I still think I'm am not getting a shift
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By Pete 55Tbird - 11 Years Ago
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( I have not felt a shift and the tack never drops off at all you would think that there would be a little fluctuation of the shift right ? 
Try this. Start in manual low. Shifter in L. Speed up to 15 MPH and read the tach. It should be higher than idle RPM. What do you see? TELL US WHAT YOU SEE.
Then let off the gas. Do you have engine braking, yes or no? TELL US.
Now start in L and at 15/20 MPH shift to D. Read the tach before and after the shift. TELL US (RPMs)
It is possible that the governor is stuck at full open and oil pressure is preventing your FOM from going into second gear. This is not very likely but it is possible. What is also unlikely is that you can go 55MPH in second gear at 3000 RPM. So check your equipment and your numbers. Pete
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By Daniel Jessup - 11 Years Ago
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Threat51 (8/27/2014)
I have not felt a shift and the tack never drops off at all you would think that there would be a little fluctuation of the shift right ?
My take - you are NOT shifting from 2nd to 3rd at all
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By PWH42 - 11 Years Ago
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One thing to bear in mind:The speedometers in mid-50s Fords are notoriously inaccurate.An indicated 55 may only be 47-50 MPH.If that's the case,you are staying in second gear.
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By Threat51 - 11 Years Ago
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I had my gps hooked up that's how I got the 55 mph.
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By Threat51 - 11 Years Ago
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I agree but how do I fix that.
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By Threat51 - 11 Years Ago
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Pete
Hers what I got at 15 in L it reads 1200 rpms
At 15 to 20 put in drive felt the shift 1100 rpms
Is eng drag when you leave off gas.
Will cheep tires on a down shift to. L
Put it just keeps going up with no shift to 3000 at 55
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By oldave57 - 11 Years Ago
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It sounds like you have pretty good evidence that the 2-3 shift is not taking place. To determine the cause of the transmission problem is pretty difficult and likely not something you can easily do with the transmission in the car. The following text comes from a 56-57 Fordomatic manual:
The shift from the intermediate to the high ratio is accomplished when the front servo (operating the front band) is released and the rear clutch is applied. This is accomplished by directing governor pressure to the face of the 2-3 shift valve and to the governor plug. As the shift valve moves inward, passages are uncovered to direct control pressure to the release side of the front servo and to the rear clutch. When both clutches are applied, the primary and secondary sun gears are locked to the turbine shaft to provide the high ratio of 1:1.
All of that means that there are several possibilities for a "no shift" condition. The governor could be sticking and not moving as the centrifugal speed increases. The rear servo and or rear clutch could be inoperative or the front servo, front band could be sticking closed. There is a procedure in the manual to remove the governor while the transmission is in the car, but beyond that, it sounds like a transmission overhaul might be in order at some point.
Good luck,
Dave
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By aussiebill - 11 Years Ago
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oldave57 (8/28/2014)
It sounds like you have pretty good evidence that the 2-3 shift is not taking place. To determine the cause of the transmission problem is pretty difficult and likely not something you can easily do with the transmission in the car. The following text comes from a 56-57 Fordomatic manual:
The shift from the intermediate to the high ratio is accomplished when the front servo (operating the front band) is released and the rear clutch is applied. This is accomplished by directing governor pressure to the face of the 2-3 shift valve and to the governor plug. As the shift valve moves inward, passages are uncovered to direct control pressure to the release side of the front servo and to the rear clutch. When both clutches are applied, the primary and secondary sun gears are locked to the turbine shaft to provide the high ratio of 1:1.
All of that means that there are several possibilities for a "no shift" condition. The governor could be sticking and not moving as the centrifugal speed increases. The rear servo and or rear clutch could be inoperative or the front servo, front band could be sticking closed. There is a procedure in the manual to remove the governor while the transmission is in the car, but beyond that, it sounds like a transmission overhaul might be in order at some point.
Good luck,
Dave
Why not try and pull the governer out , clean it and retry, its easy thing to do to rule it out.
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By Threat51 - 11 Years Ago
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Ok thanks aussiebill I guess I'll give that a try and hopefully that will take care of it.
Not much of a tranny guy.
Thanks
Bob
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By 2721955meteor - 11 Years Ago
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you can get the comp govoner out by jacking the rear of car real high,remove drive shaft,block trand pan remove rear mount remove tailshaft housing.if this isue has bin since you owned the car,ther is a posabilaty the govener was installed backwerds.(first fordamatic i did i made that mistake) it will go on the out put shaft ether way.If this isue just hapened you can remove the comp govoner and check for binding etc also ther are some seals on the output wher the govener goes that could be broken. But befor you go this rout has your linkage bin adjusted re the book.to much throttle presure will stop shift to high.also throtle presure lever could be jamed or broken. When did the isue start,since you owned the car or all of a suden.
Start from day 1 and walk us threw how the isue was noticed
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By Threat51 - 11 Years Ago
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I have only owned the car a few months and didn't think it was shifting right when I bought it but never owned one that old before .bought off dealer so no warranty .just thought rpms where to high.addjusted the linkage per manual no change.i have to take the tail shaft off to get to the govenor? Thought it was out side of the tail shaft?
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By 2721955meteor - 11 Years Ago
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if the govoner asembly was instaled backwerds you can not chang that threw the smal cover. if you have a manual you should be abel to id which way the govoner is . i will look in my 1956 motors manual for away to positively id how it should be if you do not have a manual e mail me ct1940@shaw.ca.
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By 2721955meteor - 11 Years Ago
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2721955meteor (8/30/2014)
if the govoner asembly was instaled backwerds you can not chang that threw the smal cover. if you have a manual you should be abel to id which way the govoner is . i will look in my 1956 motors manual for away to positively id how it should be if you do not have a manual e mail me ct1940@shaw.ca.
just looked in the manual,ther is a flat plate on the side of the govener it should face towards the torqeconvertor. if it faces the rear end it is incorect and you will never get 3rd speed,hope this helps. cliff
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By Threat51 - 11 Years Ago
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Hi cliff sent you email don't no if it went could use pic.
My email is
robertpwils@ gmail.com
Thanks for the help.
Should pull right out side right?
Bob
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By 2721955meteor - 11 Years Ago
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sent 2 pictures,cliff
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By 2721955meteor - 11 Years Ago
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2721955meteor (9/3/2014)
sent 2 pictures,cliff just sent some more,let me know,rechecked adress and is corect??
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