Mercomatic Park and Reverse

[RalphG]

Had the 52 Merc out for a short run today to test out the carb clean up and the new front shocks. It definitely rides and idles nice and slow now but has hesitation and almost stalls on acceleration . The accelerator pump seems to give a good shot of gas visually on both venturis so I don't think that is the problem.
Another oddity, on a cold start in park it seems to be partly in reverse too as when the engine fires up it tries to roll in reverse unless I have a block behind the wheel. Linkage adjustment maybe?

[40 Deluxe]

That would be the first thing to check. Next would be band adjustment. These early automatics also had some quirks in their oil flow circuits. I vaguely recall there being some kind of aluminum insert in the back of the input shaft that did something weird if it rotated out of position. Old shop manuals should describe this (too lazy to dig it out tonight!).

[40 Deluxe]

Oops! Reread your post. If it moves while the lever is in "Park" position, the parking pawl is not engaging. This is a linkage problem unless the pawl is broken off.

[51 MERC-CT]

Originally Posted by RalphG

Another oddity, on a cold start in park it seems to be partly in reverse too as when the engine fires up it tries to roll in reverse unless I have a block behind the wheel. Linkage adjustment maybe?

If you are saying that you are starting it while engaged in 'park', this should not happen. It should start only while engaged in 'neutral'.
If it is starting in 'park' then the neutral safety switch is either out of adjustment or is not functioning at all.

[rotorwrench]

The old Borg-O-Warner transmissions do not have vacuum modulation. It is all performed by linkage from the throttle control. The shift linkage is different than all later transmissions too. Both have to be properly adjusted for operational & smooth shift characteristics. The FoMoCo manuals and some early Motors manuals have info for adjustments on the O-Matics. When in good condition and well adjusted, they perform very well. Even better than some modern transmissions. If not adjusted well, they can get scary.

[JSeery]

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Originally Posted by 51 MERC-CT

If you are saying that you are starting it while engaged in 'park', this should not happen. It should start only while engaged in 'neutral'.
If it is starting in 'park' then the neutral safety switch is either out of adjustment or is not functioning at all.

The Merc only starts in neutral, that is interesting and I wonder why that was considered a good idea? And it doesn't have a parking pawl in park?

[rotorwrench]

The Park feature was only selected after shutting the engine off according to the OEM instructions. It has a locking pawl and should keep the car from moving while parked. Parking on a steep incline is a pain sometimes with these old trannies. They sometimes don't want to shift out of park when you get ready to start them up after parking on a hill. They will shift out of park but you always wonder if your going to break something when yarding on the selector lever. The instructions also mention that the car might creep a bit in neutral after starting a cold engine & trans. After they warm up off of fast idle the creep should go away.

[RalphG]

The neutral start switch was disconnected years ago and I thought park was a safe setting to start, more so than neutral. It could be a little dangerous when starting it standing by the fender when it tries to reverse on start up. Hence the block behind the wheel. . Busy with other stuff today but next rainy day...

[JSeery]

I had never heard of an automatic only starting in neutral, did some reading and that's the way they were designed. Seems like a poor design to me but apparently they had a reason at the time.

[51 MERC-CT]

Originally Posted by JSeery

The Merc only starts in neutral, that is interesting and I wonder why that was considered a good idea? And it doesn't have a parking pawl in park?

It's not only Merc's that have the same feature it's just about all brands that have this feature (at least all that I know of)
Witnessed two crashes, one into a wall and one into the car in front of it.
Both were early cars that the owners chose to disable the 'neutral only feature'
They found out the hard way why it's a good idea.

[JSeery]

NSS should always be used, but why the neutral start only, that seems like a safety issue to me. So your saying all the early automatics had start in neutral only? Strange. I rebuild trasmissions (mainly C4, C6, AOD, 350, 400 & T5s) and never seen that type of setup.

[rotorwrench]

There were a few automatic shift transmissions developed for production prior to the Ford-O/Merc-O-Matic types by other auto manufacturers and they all had weird operating procedures. This time frame was the infancy of production automatics so they were coming up with changes to the systems all the time. In 52 or 53 they finally put a dip stick in the engine compartment. I think the vacuum modulator came out in 54 or 55 then oil coolers were added and improved things a good bit. On the 51 cars you had to take the carpet out to get to the dip stick since it was under a cover plate there. I guess it took them a while to figure out that it might be safer to start in park under some circumstances. It was neutral start for several more years before the switches were made so they could be started in both park and neutral. The two stage Cruise-O-Matics came out in 57 or 58 and made a real 3-speed out of them.

[RalphG]

Have to admit I never knew or remembered about the "neutral only" start on the Mercomatics. This 52 has the floor panel (original missing and replaced) to check the trans. oil. It does not have an oil cooler but is air cooled with the intake on the left side and outlet on the right. I hear a few odd noises from the transmission , kind of a buzzing sound at times. Other times nothing. Just solid engagement and shifting. No sign of slippage or problems.
http://oldcarmanualproject.com/manua...rs0005_jpg.htm

[51 MERC-CT]

Originally Posted by RalphG

This 52 has the floor panel (original missing and replaced) to check the trans. oil.

This is strange because every '52-'53 Ford or Merc, I have seen has the oil pan on the trans. that connects to a tube with a dipstick in the engine compartment.
Maybe it's an early car or someone installed a '51 trans. in it.

[donald1950]

i bought a 53 car foth a ford-o-matic and it took some linkage adjustment to match the shift linkage nuteral switch position with nuteral in the transmission....

[RalphG]

Originally Posted by 51 MERC-CT

This is strange because every '52-'53 Ford or Merc, I have seen has the oil pan on the trans. that connects to a tube with a dipstick in the engine compartment.
Maybe it's an early car or someone installed a '51 trans. in it.

As far as I know it is all original but my dad bought it in 1959 so can't say what may have been changed prior to that.
Also remember that this is a Canadian built car and there are often differences from a U.S. built.

[V12Bill]

I had a 1951 Merury in about 1956, and it had a three speed transmission. Drive started the car moving in 2nd gear and low started the car in 1st gear. If you started in low, shifted into drive and pulled it back into low, it would stay in second gear until you shifted into drive again. I do recall it started in neutral only. I thought this strange , until I stalled it when starting across an intersection. It was safer to shift into neutral and restart the engine as the car coasted, than to come to a complete stop, shift into park and then restart the engine.

[RalphG]

Originally Posted by V12Bill

I had a 1951 Merury in about 1956, and it had a three speed transmission. Drive started the car moving in 2nd gear and low started the car in 1st gear. If you started in low, shifted into drive and pulled it back into low, it would stay in second gear until you shifted into drive again. I do recall it started in neutral only. I thought this strange , until I stalled it when starting across an intersection. It was safer to shift into neutral and restart the engine as the car coasted, than to come to a complete stop, shift into park and then restart the engine.

Most automatics I was familiar with always had the option of starting in park or neutral. Fords seemed to need a little jiggling of the shift lever in park to make starter contact sometimes.
Another interesting feature of the old Merc/Fordomatics, they could be push started if you could get them rolling up to 20 mph and drop into drive or low.

[rotorwrench]

The Borg Warner transmissions had front and rear pumps up until 66 or 67 so they could be pull started if so equipped. I bought a salvage yard special medium case Cruise-O for a 64 T-bird I used to have. It was from a pickup or a mail Jeep from later years and it had no rear pump. After I got the trany back together with all the good parts I found that it had a deleted pump. They just blocked off the oil ports and took the gear out. It was a small price to pay to get a working medium case trany going again. I never pull started it anyway. The car was way to low to even get under it to hook up a chain for towing.

[Motorhead6]

Originally Posted by JSeery

The Merc only starts in neutral, that is interesting and I wonder why that was considered a good idea? And it doesn't have a parking pawl in park?

All FoMoCo A/Ts started only in neutral through '56. Yes they have a parking pawl. I would guess that the linkage inside the tranny has come loose and not allowing the thing to fully engage as selected by the shifter. A quick removal of the pan and check nut torque may fix the issue.