The Ford Barn

Automotive Stud · 06-08-2022, 06:06 AM

I'm rebuilding the '49 merc overdrive transmission in my car and I found this broken pin on the workbench. It looks like more of it is missing, but I can't figure out where it came from. I thought it might be part of the overdrive shift rail, but I didn't take the overdrive apart. Also from pictures of the overdrive shift rail that appears to be stepped and this isn't. Any ideas?

Frank Miller · 06-08-2022, 08:55 AM

Been a long time since I had one apart but I think there is a pin that goes in the case between the main case and tail shaft. When you put the car in reverse it pushes the rail back to ensure no overdrive in reverse.

pistonbroke · 06-08-2022, 09:24 AM

Sorry but I don't see anything like that in my parts . I have one on the bench also. Tim

rotorwrench · 06-08-2022, 09:42 AM

I've worked on a lot of these old Merc transmissions but I've never overhauled one without full disassembly of both the front section and the rear section. That overdrive needs to be inspected too. Problems back there are more common than problems in the front section so don't ignore it.

There is a pin that holds the throw out fork to the throw out shaft. I've found bolts in them too. The shift arms are pinned to the shift cam & shaft but they are more like rivets and they aren't as big as the pictured pins. There is also a long pin that locks the reverse idler shaft to the counter shaft to insure they can't turn in the case. I don't remember them being that large a diameter either. I've never seen a lock out control break up in any way from the front actuator lever & pin to the rear rail. The pieces in the photo are similar to the rollers in the rear sprag clutch but I can't be certain if the size is right. I've never had one fall apart and I don't think they are that long. There is also a little pin in the manual overdrive lock out to hold the shaft in place but it's small.

Automotive Stud · 06-08-2022, 10:32 AM

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Thanks for the replies. My trans was working fine I just replaced the case as mine was cracked. I've already got it back together at this point and everything looks and feels right on the bench. My overdrive lockout that Frank mentioned is in place and functional. I'll go ahead and reinstall it tomorrow night and we'll see what happens.

06-08-2022, 08:55 AM	#2
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	Re: Overdrive transmission part? Been a long time since I had one apart but I think there is a pin that goes in the case between the main case and tail shaft. When you put the car in reverse it pushes the rail back to ensure no overdrive in reverse. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

06-08-2022, 09:24 AM	#3
pistonbroke Senior Member Join Date: Feb 2021 Location: Perry Mo. Posts: 486	Re: Overdrive transmission part? Sorry but I don't see anything like that in my parts . I have one on the bench also. Tim

06-08-2022, 09:42 AM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: Overdrive transmission part? I've worked on a lot of these old Merc transmissions but I've never overhauled one without full disassembly of both the front section and the rear section. That overdrive needs to be inspected too. Problems back there are more common than problems in the front section so don't ignore it. There is a pin that holds the throw out fork to the throw out shaft. I've found bolts in them too. The shift arms are pinned to the shift cam & shaft but they are more like rivets and they aren't as big as the pictured pins. There is also a long pin that locks the reverse idler shaft to the counter shaft to insure they can't turn in the case. I don't remember them being that large a diameter either. I've never seen a lock out control break up in any way from the front actuator lever & pin to the rear rail. The pieces in the photo are similar to the rollers in the rear sprag clutch but I can't be certain if the size is right. I've never had one fall apart and I don't think they are that long. There is also a little pin in the manual overdrive lock out to hold the shaft in place but it's small. Last edited by rotorwrench; 06-08-2022 at 09:49 AM.

06-08-2022, 10:32 AM	#5
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Re: Overdrive transmission part? Sponsored Links (Register now to hide all advertisements) Thanks for the replies. My trans was working fine I just replaced the case as mine was cracked. I've already got it back together at this point and everything looks and feels right on the bench. My overdrive lockout that Frank mentioned is in place and functional. I'll go ahead and reinstall it tomorrow night and we'll see what happens.