The Ford Barn

Automotive Stud · 06-11-2022, 04:27 PM

I put together a 49 merc column shift transmission with overdrive from a good case, Zephyr gears I had that looked good, and new bearings and syncros. I took it for its first drive today and it pops out of second most of the time as soon as I let off the clutch under acceleration. Once in a while the shifter feels like it bites in just a little more and it doesn't grind or pop out, but most of the time it does. I adjusted the clutch and shift linkage but no joy. I hate to pull the trans again but I will if I have to. Could I have installed the fork in the side cover backwards? Anything else I can check or adjust without taking it out again?

Ken/Alabama · 06-11-2022, 07:16 PM

Usually happens because of too much clearance between the second gear and synchro hub. It should be .004-.008. Other thing can be worn gears, worn case that creates too much clearance on the cluster. Also the ball and spring detention in the shift cover.

rotorwrench · 06-11-2022, 08:01 PM

2nd has a lot of thrust loading on it and so does the countershaft cluster gear in 2nd gear. The helical gears make thrust one way under acceleration and the other way under deceleration. Too much play with either gear will invite thrust related issues. The second gear has an internal bushing that can wear too. Solid shift detents will help some but sloppy function can overpower the detent.

When I overhaul these old cog boxes I make sure all the wear spots are restored to as close to new specs as I can get. This can include worn main shaft and countershaft journals as well as all the bearings and thrust washers. These units are old and some were road hard.

Automotive Stud · 06-11-2022, 08:48 PM

Thanks guys, I replaced the thrust washers also, the cluster gear was so tight I had to sand down the babbitt on the rear thrust washer so I could get the cluster gear to spin. I'll see if I can pull the side cover off with it in the car and inspect second gear to synchro hub. The side cover was on another trans that I never had problems with.

rotorwrench · 06-12-2022, 11:55 AM

The shift fork cams generally only go one way due to the detents. I hope this is an overdrive type side cover. It has to have the reverse lock out. I'd check the synchro sleeve and hub. If it's turned around then that would be a major problem.

Another situation you may have is that the LZ gears and specifically the 24 tooth 2nd gear, may not be compatible with the later main shaft set up as it normally is but I don't know for certain. I've never heard of anyone using the LZ gears in a 49 thru early 51 Mercury transmission. LZ gears went through two changes in the years before 1949. The sets will fit the Ford transmissions up through 1948 as long as the Lincoln specific parts are stacked up and matched for tooth count but I don't know about the later Mercury car transmissions up to early 1951. After early 1951 the gears all changed to a new design with no backward compatibility on piece parts. Lincolns used a completely different transmission from 1949 on.

Automotive Stud · 06-13-2022, 09:16 AM

Sponsored Links (Register now to hide all advertisements)

It is the correct OD side cover. Syncro sleeve is in correctly. I don't see why the LZ gears wouldn't work, it all seemed to go together okay. Here's a pic I took when assembling it prior to the input shaft being installed. My next step is going to be pull the side cover with it still in the car, maybe I can see something obviously wrong, otherwise I'll have to pull it back out.

Bored&Stroked · 06-13-2022, 09:31 AM

What I have usually found is it is related to clearances and wear. If the caged-roller bearing surface on the front of the mainshaft has any wear, that is an issue. You want the end-play on the 2nd gear stack-up to be on the LOW side of the spec. I usually shoot for about .003 to .004 max. Usually I have to tune the thrust washers related to 2nd gear - or even the thickness of 2nd gear itself. Also, I have had Charlie NY re-bush 2nd gear for the specific main-shaft it is going on - to actually achieve a little bit of a drag in the fitment. Part of the challenge is that it is hard to find NOS main shafts, NOS caged rollers, NOS cluster shafts, etc.. So, we tend to have to settle for the best used stuff we can find and/or use the re-pop stuff. The re-pop caged rollers have been an issue for me, the re-pop cluster shafts have been an issue for me . . . and on and on . . .

In the end, one wants the least bearing play, clearances, etc.. -- as that seems to be the only way I can get these transmissions to stay in 2nd (especially coming off of a higher RPM). Even when I do ALL the above exactly right, seems that they continue to work correctly for only a year or two . . . then it is back to 2nd wanting to pop out.

I've recently been developing a new skill . . . using my right knee on the 39' swan neck shift lever to hold it in second as I come off of a higher RPM situation and still need both hands to steer! Beats the heck out of a "hook on the dash" like most of the race cars used to have. LOL

I wish we had sources for NOS parts . . . this would be a lot easier.

Charlie ny · 06-13-2022, 09:43 AM

Stud,
What I see is the 2nd gear syncro smack up against 2nd gear plus there appears to be foreign material in between a couple teeth on the slider gear. Both need attention.
Use great care when replacing syncro rings. Unless NOS he 3 steps may require remachining for depth and establishing the correct relationship to the 'cone'.
Charlie ny

Charlie n y

Tim Ayers · 06-13-2022, 11:34 AM

Like others have mentioned and I'm assuming you've done this, tolerance and end play is super crucial. Only way to do this is to have the rear retainer and u-joint on and to torque. It's kind of a pain in the ass if not right the first time for it needs to come apart and done again.

Were the thrust surfaces in the case OK?

With my recent AV8 build, this was the first complete trans rebuild I did. I was so worried it wouldn't work, but following Mac VP's book to the letter, it works flawlessly.

I did collect NOS shafts, cage bearings, cluster gears and top and forks along the way. The case was a good as NOS.

I hope you figure this out since it's a lot of work to take in and out. Good luck.

rotorwrench · 06-13-2022, 07:11 PM

Charlie has a point. There should be a gap between the blocker ring brass teeth and the teeth on the gear. A quarter should fit the gap in between them. That brass blocker ring acts as both a brake and a spacer to ease the mesh up of the synchro hub and second gear.

Automotive Stud · 06-13-2022, 07:39 PM

Humm, we might be on to something here. What would cause the synchro ring to sit too low on the gear? I put new synchro rings in it....

Charlie ny · 06-13-2022, 08:34 PM

Stud,
It is a cruel world....new does not mean correct. The trans has to come out
that's that. Contact your vendor and describe the issue with the ring...be sure 3rd gear syncro ring is not suffering too. In the past a now defunct vendor put a shine on used syncros so they looked new....
That foreign material stuck in the root of the two teeth on the slider may be

just as cruel as the syncro fubar....don't let that pass on by.
Charlie ny

Terry,OH · 06-14-2022, 06:21 AM

I suggest taking it apart and trying the other syncro blocker ring on 2nd gear to see if it also goes on too far.

Ol' Ron · 06-14-2022, 06:44 AM

I think the case has starched. Back in the days before we knew what we were doing we measures the distance between the front and rear snap rings and then measured the case. Machined the case tot hat dimention. Now I think the stock dim should be available. This is one reason I use modern components like T-170s and Spicer rears. But, I have a grear deal of respect for those that can fix this stuff, better man than I.
Gramps

Automotive Stud · 06-14-2022, 10:07 AM

Thanks for all of the advice. It's funny, my old synchros didn't look bad and they were stamped USA, but I put new ones in anyway. They might be going back in this weekend, I'll keep everyone posted...

Tim Ayers · 06-14-2022, 10:10 AM

Quote:

Originally Posted by Automotive Stud

Thanks for all of the advice. It's funny, my old synchros didn't look bad and they were stamped USA, but I put new ones in anyway. They might be going back in this weekend, I'll keep everyone posted...

Curious, if the side cover is still off, can you spin the synchro fairly easily?

Juergen · 06-14-2022, 02:42 PM

[QUOTE=Bored&Stroked;2138376]What I have usually found is it is related to clearances and wear. If the caged-roller bearing surface on the front of the mainshaft has any wear, that is an issue. You want the end-play on the 2nd gear stack-up to be on the LOW side of the spec. I usually shoot for about .003 to .004 max.

Bored and Stroked pointed this out. The 49 Merc has an open drive output. So there is no U-joint to lock the output shaft to the case. The input shaft also has some leeway to wobble. I always wondered if we needed such tight tolerances with the closed drive shaft trans, why these open drive trans didn't pop out of gear from the start. The clearances on the mainshaft, the caged roller and the input shaft have to be low. I would definitely look here. Using a NOS cage instead of a repro cage did the trick on one of my builds.

rotorwrench · 06-15-2022, 10:50 AM

There is a C-ring or snap-ring that holds the tail shaft and there are rings on the other shafts plus the lock for the sprag to shaft. Mac VP is the only supplier of correct width replacement snap rings for the old Ford transmissions. His are also made so they can be easily removed when needed. The OEM snap rings are NOT easy to remove. Sloppy snap rings can allow play and many of the average replacements are too thin.

Automotive Stud · 06-17-2022, 06:41 AM

I finally took the side cover off. I wish I saw something obviously wrong but I didn't. Is anything jumping out to anyone else? Also, here's a video I made also. https://youtu.be/7blI5cqi66o

Bored&Stroked · 06-17-2022, 07:08 AM

You'll not be able to diagnose the issue by looking at it - I only wish it were that easy. You'll have to take it all apart and start the process of really checking clearances, wear, etc..

Outside of incorrect synchros, the most important are:

1) The stack-up of second gear (end-play)
2) The condition of the front of the main-shaft and the bearing it goes in
3) The tightness of the 2nd gear bushing.

It is kind of a "compounding" situation - the more slop in all three of these areas, the more chances to pop out of second.

As noted earlier, I have Charlie NY re-bush second to exactly fit the specific main shaft I'm using. Also, I frequently test fit a couple different main shafts to front input shafts - to see where I have the least potential deflection (I do this on a lathe).

I'm not sure if NOS main shafts are available for your trans, but mic the front caged rolled bearing surface. It needs to have no wear! If it is possible to find NOS main shafts - without rust all over them, I'd pick one up for sure.

06-11-2022, 04:27 PM	#1
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Transmission pops out of second I put together a 49 merc column shift transmission with overdrive from a good case, Zephyr gears I had that looked good, and new bearings and syncros. I took it for its first drive today and it pops out of second most of the time as soon as I let off the clutch under acceleration. Once in a while the shifter feels like it bites in just a little more and it doesn't grind or pop out, but most of the time it does. I adjusted the clutch and shift linkage but no joy. I hate to pull the trans again but I will if I have to. Could I have installed the fork in the side cover backwards? Anything else I can check or adjust without taking it out again?

06-11-2022, 07:16 PM	#2
Ken/Alabama Senior Member Join Date: May 2010 Location: Alabama Posts: 3,257	Re: Transmission pops out of second Usually happens because of too much clearance between the second gear and synchro hub. It should be .004-.008. Other thing can be worn gears, worn case that creates too much clearance on the cluster. Also the ball and spring detention in the shift cover.

06-11-2022, 08:01 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Transmission pops out of second 2nd has a lot of thrust loading on it and so does the countershaft cluster gear in 2nd gear. The helical gears make thrust one way under acceleration and the other way under deceleration. Too much play with either gear will invite thrust related issues. The second gear has an internal bushing that can wear too. Solid shift detents will help some but sloppy function can overpower the detent. When I overhaul these old cog boxes I make sure all the wear spots are restored to as close to new specs as I can get. This can include worn main shaft and countershaft journals as well as all the bearings and thrust washers. These units are old and some were road hard.

06-11-2022, 08:48 PM	#4
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Re: Transmission pops out of second Thanks guys, I replaced the thrust washers also, the cluster gear was so tight I had to sand down the babbitt on the rear thrust washer so I could get the cluster gear to spin. I'll see if I can pull the side cover off with it in the car and inspect second gear to synchro hub. The side cover was on another trans that I never had problems with.

06-12-2022, 11:55 AM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Transmission pops out of second The shift fork cams generally only go one way due to the detents. I hope this is an overdrive type side cover. It has to have the reverse lock out. I'd check the synchro sleeve and hub. If it's turned around then that would be a major problem. Another situation you may have is that the LZ gears and specifically the 24 tooth 2nd gear, may not be compatible with the later main shaft set up as it normally is but I don't know for certain. I've never heard of anyone using the LZ gears in a 49 thru early 51 Mercury transmission. LZ gears went through two changes in the years before 1949. The sets will fit the Ford transmissions up through 1948 as long as the Lincoln specific parts are stacked up and matched for tooth count but I don't know about the later Mercury car transmissions up to early 1951. After early 1951 the gears all changed to a new design with no backward compatibility on piece parts. Lincolns used a completely different transmission from 1949 on. Last edited by rotorwrench; 06-12-2022 at 12:37 PM.

06-13-2022, 09:31 AM	#7
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,062	Re: Transmission pops out of second What I have usually found is it is related to clearances and wear. If the caged-roller bearing surface on the front of the mainshaft has any wear, that is an issue. You want the end-play on the 2nd gear stack-up to be on the LOW side of the spec. I usually shoot for about .003 to .004 max. Usually I have to tune the thrust washers related to 2nd gear - or even the thickness of 2nd gear itself. Also, I have had Charlie NY re-bush 2nd gear for the specific main-shaft it is going on - to actually achieve a little bit of a drag in the fitment. Part of the challenge is that it is hard to find NOS main shafts, NOS caged rollers, NOS cluster shafts, etc.. So, we tend to have to settle for the best used stuff we can find and/or use the re-pop stuff. The re-pop caged rollers have been an issue for me, the re-pop cluster shafts have been an issue for me . . . and on and on . . . In the end, one wants the least bearing play, clearances, etc.. -- as that seems to be the only way I can get these transmissions to stay in 2nd (especially coming off of a higher RPM). Even when I do ALL the above exactly right, seems that they continue to work correctly for only a year or two . . . then it is back to 2nd wanting to pop out. I've recently been developing a new skill . . . using my right knee on the 39' swan neck shift lever to hold it in second as I come off of a higher RPM situation and still need both hands to steer! Beats the heck out of a "hook on the dash" like most of the race cars used to have. LOL I wish we had sources for NOS parts . . . this would be a lot easier.

06-13-2022, 09:43 AM	#8
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Transmission pops out of second Stud, What I see is the 2nd gear syncro smack up against 2nd gear plus there appears to be foreign material in between a couple teeth on the slider gear. Both need attention. Use great care when replacing syncro rings. Unless NOS he 3 steps may require remachining for depth and establishing the correct relationship to the 'cone'. Charlie ny Charlie n y

06-13-2022, 11:34 AM	#9
Tim Ayers Senior Member Join Date: May 2010 Location: NJ Posts: 6,177	Re: Transmission pops out of second Like others have mentioned and I'm assuming you've done this, tolerance and end play is super crucial. Only way to do this is to have the rear retainer and u-joint on and to torque. It's kind of a pain in the ass if not right the first time for it needs to come apart and done again. Were the thrust surfaces in the case OK? With my recent AV8 build, this was the first complete trans rebuild I did. I was so worried it wouldn't work, but following Mac VP's book to the letter, it works flawlessly. I did collect NOS shafts, cage bearings, cluster gears and top and forks along the way. The case was a good as NOS. I hope you figure this out since it's a lot of work to take in and out. Good luck. Last edited by Tim Ayers; 06-13-2022 at 11:46 AM.

06-13-2022, 07:11 PM	#10
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Transmission pops out of second Charlie has a point. There should be a gap between the blocker ring brass teeth and the teeth on the gear. A quarter should fit the gap in between them. That brass blocker ring acts as both a brake and a spacer to ease the mesh up of the synchro hub and second gear.

06-13-2022, 07:39 PM	#11
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Re: Transmission pops out of second Humm, we might be on to something here. What would cause the synchro ring to sit too low on the gear? I put new synchro rings in it....

06-13-2022, 08:34 PM	#12
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Transmission pops out of second Stud, It is a cruel world....new does not mean correct. The trans has to come out that's that. Contact your vendor and describe the issue with the ring...be sure 3rd gear syncro ring is not suffering too. In the past a now defunct vendor put a shine on used syncros so they looked new.... That foreign material stuck in the root of the two teeth on the slider may be just as cruel as the syncro fubar....don't let that pass on by. Charlie ny

06-14-2022, 06:21 AM	#13
Terry,OH Senior Member Join Date: May 2010 Posts: 4,746	Re: Transmission pops out of second I suggest taking it apart and trying the other syncro blocker ring on 2nd gear to see if it also goes on too far.

06-14-2022, 06:44 AM	#14
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,858	Re: Transmission pops out of second I think the case has starched. Back in the days before we knew what we were doing we measures the distance between the front and rear snap rings and then measured the case. Machined the case tot hat dimention. Now I think the stock dim should be available. This is one reason I use modern components like T-170s and Spicer rears. But, I have a grear deal of respect for those that can fix this stuff, better man than I. Gramps

06-14-2022, 10:07 AM	#15
Automotive Stud Senior Member Join Date: May 2010 Location: New Jersey Posts: 832	Re: Transmission pops out of second Thanks for all of the advice. It's funny, my old synchros didn't look bad and they were stamped USA, but I put new ones in anyway. They might be going back in this weekend, I'll keep everyone posted...

06-14-2022, 02:42 PM	#17
Juergen Senior Member Join Date: May 2010 Posts: 500	Re: Transmission pops out of second [QUOTE=Bored&Stroked;2138376]What I have usually found is it is related to clearances and wear. If the caged-roller bearing surface on the front of the mainshaft has any wear, that is an issue. You want the end-play on the 2nd gear stack-up to be on the LOW side of the spec. I usually shoot for about .003 to .004 max. Bored and Stroked pointed this out. The 49 Merc has an open drive output. So there is no U-joint to lock the output shaft to the case. The input shaft also has some leeway to wobble. I always wondered if we needed such tight tolerances with the closed drive shaft trans, why these open drive trans didn't pop out of gear from the start. The clearances on the mainshaft, the caged roller and the input shaft have to be low. I would definitely look here. Using a NOS cage instead of a repro cage did the trick on one of my builds.

06-15-2022, 10:50 AM	#18
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Transmission pops out of second There is a C-ring or snap-ring that holds the tail shaft and there are rings on the other shafts plus the lock for the sprag to shaft. Mac VP is the only supplier of correct width replacement snap rings for the old Ford transmissions. His are also made so they can be easily removed when needed. The OEM snap rings are NOT easy to remove. Sloppy snap rings can allow play and many of the average replacements are too thin.

06-17-2022, 07:08 AM	#20
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,062	Re: Transmission pops out of second You'll not be able to diagnose the issue by looking at it - I only wish it were that easy. You'll have to take it all apart and start the process of really checking clearances, wear, etc.. Outside of incorrect synchros, the most important are: 1) The stack-up of second gear (end-play) 2) The condition of the front of the main-shaft and the bearing it goes in 3) The tightness of the 2nd gear bushing. It is kind of a "compounding" situation - the more slop in all three of these areas, the more chances to pop out of second. As noted earlier, I have Charlie NY re-bush second to exactly fit the specific main shaft I'm using. Also, I frequently test fit a couple different main shafts to front input shafts - to see where I have the least potential deflection (I do this on a lathe). I'm not sure if NOS main shafts are available for your trans, but mic the front caged rolled bearing surface. It needs to have no wear! If it is possible to find NOS main shafts - without rust all over them, I'd pick one up for sure.