The Ford Barn

tubman · 04-08-2017, 09:45 AM

I don't want to hijack the thread by "old guy rich", so I'll start a new one. I have two Ford OD transmissions, a '50 and a '51. I read somewhere that you can check the OD unit by either engaging and disengaging the OD, and turning the output shaft. In one case you should be able to turn the output shaft while holding the input shaft because of the "freewheeling feature. I've tried this on both of my transmissions in both positions, and I can't get them to do this. How much effort should it take? I have arthritis in my right hand and it doesn't have much strength. Also, it's hard to get a grip on the output shaft. Should I put a slip joint on the shaft to get a better grip. Should it turn easily or should it take some effort? I believe it should be in overdrive mode when doing this so it freewheels.

I have always wanted to have an overdrive in my '51, and "Rich's" thread has re-invigorated me. If the '50 is good and the '51 is bad, I think I would have to change the guts, because the '50 and '51 tailhousings are different. How difficult is this? I have rebuilt a few transmissions, so I'm not entirely without experience (or snap ring pliers).

40 Deluxe · 04-08-2017, 11:33 AM

Older Motor Manuals have detailed procedures. One thing I remember is holding the over running clutch rollers in place with a rubber band as you assemble it. The band gets pushed off and stays in the trans.
On your testing, first the lockout lever has to be in the disengaged position (to the rear, if I remember). Then turn the output shaft counterclockwise (looking from the rear-normal forward rotation). It should freewheel-input not turning with trans in high. Turning the other direction (backwards) the input should turn. Shifting into reverse uses internal linkage to activate the lockout so it will not freewheel in reverse. This is necessary because, by design, you cannot back up if the overdrive solenoid is engaged. It is in effect like in two gears at once. The car will not move or something breaks.
Next, energize the solenoid with a 6 V. battery, lockout lever in released position, trans in high, and turn input in normal direction. Output should turn faster than input if O/D is working. You should hear and feel solenoid engaging.
I agree, these are neat trannies. The governor only allows O/D to engage above 27 MPH. Below that speed it freewheels when you let off the gas. Above that speed O/D automatically engages when you let off the gas. So if you want to wind out in low above 27 MPH, let off momentarily, you're in O/D low and good for maybe 40 MPH before hitting 2nd. Then floor the gas so the trans kicks down out of O/D into 2nd direct, wind it out again, briefly let off, and you're in 2nd O/D. Same in high. So you have a 6 speed trans!
On a more practical note, the kickdown feature made an excellent passing gear (what it was designed for). O/D rear gears were usually 4.11 and the O/D ratio made it like about 3.10 to 1. The engine was running at too low RPM for good passing power. So when you floored it, the trans immediately kicked back down to direct drive, you got the 4.11 ratio back, and around that slow car you went, and back into your lane before oncoming traffic got too close.
If you didn't want freewheeling around town, you pulled out the lockout knob (labeled "overdrive"), or if coming to a long downhill, briefly floor the gas to kick it down to direct, and pull out the knob for better engine braking.

tubman · 04-08-2017, 12:34 PM

Thanks "40 Deluxe" for the information (i bet the "rubber band" trick saved a lot of frustration. I had a '51 with a properly working OD when I was in high school in the fifties, so I know the benefits. Now I just have to get the ambition to crawl around under this thing to install it. I think it may be time to buy a lift.

rotorwrench · 04-08-2017, 04:43 PM

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On an older OD gearbox that has been setting around for a while, you will need to disassemble and check out all the parts first hand. I have heard some horror stories about failures in these old Borg Warner designs and it pays to make sure everything in there is good to go. The planetary gears are small and they need to be in very good condition to start out with. There is only one way to check that. The balk ring should have a bit of drag left in it or it won't shift right. These transmissions are really relatively simple but you do need some heavy duty snap ring pliers. I replace all the backwards rings with new ones from Mac VanPelt. His are the correct width too. Those are the hardest damn things to get off but with the new ones they will be easy to get on and off on the next go around.

The last Mercury type I opened up was in pretty good shape. All I had to replace was the usual stuff. Bearings, thrust washers, gaskets, those snap rings, and the low gear & cluster due to chipped teeth. Mac had all the good stuff and I can't tell you enough how well his transmission book helps, even on the OD transmissions since a lot of the parts were the same in the Mercury transmissions. You do still need a good OD transmission guide though. I use the 49 thru 51 Lincoln Mercury overhaul manual myself but Ford and Borg Warner made some good manuals too.

04-08-2017, 09:45 AM	#1
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 11,637	Checking an overdrive unit I don't want to hijack the thread by "old guy rich", so I'll start a new one. I have two Ford OD transmissions, a '50 and a '51. I read somewhere that you can check the OD unit by either engaging and disengaging the OD, and turning the output shaft. In one case you should be able to turn the output shaft while holding the input shaft because of the "freewheeling feature. I've tried this on both of my transmissions in both positions, and I can't get them to do this. How much effort should it take? I have arthritis in my right hand and it doesn't have much strength. Also, it's hard to get a grip on the output shaft. Should I put a slip joint on the shaft to get a better grip. Should it turn easily or should it take some effort? I believe it should be in overdrive mode when doing this so it freewheels. I have always wanted to have an overdrive in my '51, and "Rich's" thread has re-invigorated me. If the '50 is good and the '51 is bad, I think I would have to change the guts, because the '50 and '51 tailhousings are different. How difficult is this? I have rebuilt a few transmissions, so I'm not entirely without experience (or snap ring pliers).

04-08-2017, 11:33 AM	#2
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,818	Re: Checking an overdrive unit Older Motor Manuals have detailed procedures. One thing I remember is holding the over running clutch rollers in place with a rubber band as you assemble it. The band gets pushed off and stays in the trans. On your testing, first the lockout lever has to be in the disengaged position (to the rear, if I remember). Then turn the output shaft counterclockwise (looking from the rear-normal forward rotation). It should freewheel-input not turning with trans in high. Turning the other direction (backwards) the input should turn. Shifting into reverse uses internal linkage to activate the lockout so it will not freewheel in reverse. This is necessary because, by design, you cannot back up if the overdrive solenoid is engaged. It is in effect like in two gears at once. The car will not move or something breaks. Next, energize the solenoid with a 6 V. battery, lockout lever in released position, trans in high, and turn input in normal direction. Output should turn faster than input if O/D is working. You should hear and feel solenoid engaging. I agree, these are neat trannies. The governor only allows O/D to engage above 27 MPH. Below that speed it freewheels when you let off the gas. Above that speed O/D automatically engages when you let off the gas. So if you want to wind out in low above 27 MPH, let off momentarily, you're in O/D low and good for maybe 40 MPH before hitting 2nd. Then floor the gas so the trans kicks down out of O/D into 2nd direct, wind it out again, briefly let off, and you're in 2nd O/D. Same in high. So you have a 6 speed trans! On a more practical note, the kickdown feature made an excellent passing gear (what it was designed for). O/D rear gears were usually 4.11 and the O/D ratio made it like about 3.10 to 1. The engine was running at too low RPM for good passing power. So when you floored it, the trans immediately kicked back down to direct drive, you got the 4.11 ratio back, and around that slow car you went, and back into your lane before oncoming traffic got too close. If you didn't want freewheeling around town, you pulled out the lockout knob (labeled "overdrive"), or if coming to a long downhill, briefly floor the gas to kick it down to direct, and pull out the knob for better engine braking.

04-08-2017, 12:34 PM	#3
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 11,637	Re: Checking an overdrive unit Thanks "40 Deluxe" for the information (i bet the "rubber band" trick saved a lot of frustration. I had a '51 with a properly working OD when I was in high school in the fifties, so I know the benefits. Now I just have to get the ambition to crawl around under this thing to install it. I think it may be time to buy a lift.

04-08-2017, 04:43 PM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 17,410	Re: Checking an overdrive unit Sponsored Links (Register now to hide all advertisements) On an older OD gearbox that has been setting around for a while, you will need to disassemble and check out all the parts first hand. I have heard some horror stories about failures in these old Borg Warner designs and it pays to make sure everything in there is good to go. The planetary gears are small and they need to be in very good condition to start out with. There is only one way to check that. The balk ring should have a bit of drag left in it or it won't shift right. These transmissions are really relatively simple but you do need some heavy duty snap ring pliers. I replace all the backwards rings with new ones from Mac VanPelt. His are the correct width too. Those are the hardest damn things to get off but with the new ones they will be easy to get on and off on the next go around. The last Mercury type I opened up was in pretty good shape. All I had to replace was the usual stuff. Bearings, thrust washers, gaskets, those snap rings, and the low gear & cluster due to chipped teeth. Mac had all the good stuff and I can't tell you enough how well his transmission book helps, even on the OD transmissions since a lot of the parts were the same in the Mercury transmissions. You do still need a good OD transmission guide though. I use the 49 thru 51 Lincoln Mercury overhaul manual myself but Ford and Borg Warner made some good manuals too.