The Ford Barn

Dick Webber · 02-07-2018, 08:50 PM

For years I have been accumulating parts to change my stock 49 Mercury to overdrive.

The completed unit is assembled but with cover off it turns freely in neutral but will only shift into second. When shifting to high, low or reverse it will only turn a few degrees.

The 28 tooth cluster appears New and has the right tooth count. I have have checked the tooth count on all gears. I disassembled and reassembled to check for errors and found none. The overdrive turns freely and will free wheel with lever forward.

After I put it together again today it did the same thing. I'm no mechanic but I've done this a dozen times over 60 years. Had the shop manual in front of me.

I'm stumped. Anyone have any ideas?

Alaska Jim · 02-08-2018, 12:41 AM

I am by no means an expert, but maybe the reverse lock out shift rail is not working correctly. rotorwrench here on the barn is very familiar with the o/d trans. maybe he can give you some ideas

expavr · 02-08-2018, 03:39 AM

“The overdrive turns freely and will free wheel with lever forward. “

If the lever you’re referring to is the one that locks up the O/D and its all the way forward the O/D function should be locked out and the transmission shouldn’t be free wheeling. When you turn the input shaft with second gear engaged does the output shaft turn? I doubt that the shift rail is the source of this problem, but it sounds like there is an issue with how its interacting (or not) with the O/D which should be checked out.

Frank Miller · 02-08-2018, 07:59 AM

Is the solenoid attached? If the balk ring is engaged with the od lever locked out it won't work.

rotorwrench · 02-08-2018, 10:53 AM

The overdrive control should be in the locked out position to test the transmission shift function. The input needs a bit of rotation to get tooth alignment for the gears & blockers to mesh. If the thing won't shift from 2nd to high then there may be a problem with the synchronizer. The reverse gear selection pushes a lever that in turn pushes the lock out rail inside. If the OD is in lock out then reverse should go in. As Frank mentioned, the overdrive will not lock out if the actuator pawl is fully engaged with the balk ring. It has to be in the fully disengaged position. If not, the shift rail can't move to block the pawl.

expavr · 02-08-2018, 12:47 PM

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Attached are photos of the gears and shift forks in my 49 Merc O/D trans. Maybe you can use these photos to compare your final assembly with the one in this trans. I took these photos while bench testing my rebuild and all the gears functioned properly. Note that the O/D shift rail in the upper right corner of the trans case is protruding into the transmission which means that the O/D unit is locked up - no free wheeling. Also when I was bench testing the trans the solenoid wasn't installed in the transmission. The thought had occurred to me that there might be an issue with your solenoid (the pawl bound up or weak spring) that's causing it to stay engaged with the balk ring. Just a thought.

Dick Webber · 02-08-2018, 09:13 PM

Wow! That is a real pretty transmission!

To clarify:
I am testing this unit with the overdrive lever in the lockout position, no solenoid attached, shifting cover off, and out of car. I made a tool to pull the balk ring out and I believe it is in position where I could attach the solenoid

The final drive does not freewheel and the unit works fine in second and neutral.

I am not in 2 gears at once

To test the overdrive for freewheeling I engaged the lockout lever and the output shift will freewheel.

The baffling thing is, if it turns in neutral and second, why doesn't high work? It's not stuck as the main drive will turn, but only a few degrees.

I'm going to try another synchronizer but even if it fixes high that doesn't explain low and reverse.

The cluster is 28-24-16-14 with a 16 tooth main and 29 tooth slider. I hope I remember this right. Notes are at the shop. It all turns smooth in neutral.

And if the synchro change doesn't work I have a conventional tail housing I can install to isolate a possible overdrive problem.

Thank you all for your ideas.

02-07-2018, 08:50 PM	#1
Dick Webber Senior Member Join Date: May 2010 Location: Bowling Green KY Posts: 337	49 Mercury overdrive transmission assembly question For years I have been accumulating parts to change my stock 49 Mercury to overdrive. The completed unit is assembled but with cover off it turns freely in neutral but will only shift into second. When shifting to high, low or reverse it will only turn a few degrees. The 28 tooth cluster appears New and has the right tooth count. I have have checked the tooth count on all gears. I disassembled and reassembled to check for errors and found none. The overdrive turns freely and will free wheel with lever forward. After I put it together again today it did the same thing. I'm no mechanic but I've done this a dozen times over 60 years. Had the shop manual in front of me. I'm stumped. Anyone have any ideas?

02-08-2018, 12:41 AM	#2
Alaska Jim Senior Member Join Date: May 2010 Location: Palmer, Alaska Posts: 1,575	Re: 49 Mercury overdrive transmission assembly question I am by no means an expert, but maybe the reverse lock out shift rail is not working correctly. rotorwrench here on the barn is very familiar with the o/d trans. maybe he can give you some ideas

02-08-2018, 03:39 AM	#3
expavr Senior Member Join Date: May 2010 Location: Hansville, WA Posts: 776	Re: 49 Mercury overdrive transmission assembly question “The overdrive turns freely and will free wheel with lever forward. “ If the lever you’re referring to is the one that locks up the O/D and its all the way forward the O/D function should be locked out and the transmission shouldn’t be free wheeling. When you turn the input shaft with second gear engaged does the output shaft turn? I doubt that the shift rail is the source of this problem, but it sounds like there is an issue with how its interacting (or not) with the O/D which should be checked out.

02-08-2018, 07:59 AM	#4
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	Re: 49 Mercury overdrive transmission assembly question Is the solenoid attached? If the balk ring is engaged with the od lever locked out it won't work. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

02-08-2018, 10:53 AM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,431	Re: 49 Mercury overdrive transmission assembly question The overdrive control should be in the locked out position to test the transmission shift function. The input needs a bit of rotation to get tooth alignment for the gears & blockers to mesh. If the thing won't shift from 2nd to high then there may be a problem with the synchronizer. The reverse gear selection pushes a lever that in turn pushes the lock out rail inside. If the OD is in lock out then reverse should go in. As Frank mentioned, the overdrive will not lock out if the actuator pawl is fully engaged with the balk ring. It has to be in the fully disengaged position. If not, the shift rail can't move to block the pawl.

02-08-2018, 09:13 PM	#7
Dick Webber Senior Member Join Date: May 2010 Location: Bowling Green KY Posts: 337	Re: 49 Mercury overdrive transmission assembly question Wow! That is a real pretty transmission! To clarify: I am testing this unit with the overdrive lever in the lockout position, no solenoid attached, shifting cover off, and out of car. I made a tool to pull the balk ring out and I believe it is in position where I could attach the solenoid The final drive does not freewheel and the unit works fine in second and neutral. I am not in 2 gears at once To test the overdrive for freewheeling I engaged the lockout lever and the output shift will freewheel. The baffling thing is, if it turns in neutral and second, why doesn't high work? It's not stuck as the main drive will turn, but only a few degrees. I'm going to try another synchronizer but even if it fixes high that doesn't explain low and reverse. The cluster is 28-24-16-14 with a 16 tooth main and 29 tooth slider. I hope I remember this right. Notes are at the shop. It all turns smooth in neutral. And if the synchro change doesn't work I have a conventional tail housing I can install to isolate a possible overdrive problem. Thank you all for your ideas.