Jumping out of second gear?

JackA

JackA

Senior Member
I am aware that the jumping out of gear results from the rounding over of the teeth on the gear. I also am a newby to the Model A and am wondering if there is any cure, short of rebuilding the ******.
 
I was under the impression that jumping out of gear was more a symptom of a worn input shaft /pilot bearing interface and misalignment with the flywheel, or a transmission tower issue with worn shift forks and/or detents. I would pull the tower and check the visual condition of the gears, and if ok rebuild the tower first.
 
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Worn input shaft and pilot bearing effects third gear . The plungers and spring that fits in the transmission top cover can have an effect on jumping out of second gear. There is a screw in the right front side that can be removed to replace the plunger and spring. The plunger and spring set only cost $4.95 and is worth a try. This isn't the spring that holds the shift lever in place
 
After just having rebuilt my transmission, I noticed that the car jumped out of 2nd going uphill only. The cause ---- a weak detent spring. This turned out to be a quick and cheap fix.

Peyton
 
Misalignment between the flywheel and the transmission can cause it to jump out of gear. The alignment of the flywheel housing and the back of the engine block is a factor. There are supposed to be horseshoe shape .010 metal shims located between the two ears of the flywheel housing and the engine block where the throttle linkage bolts. These shims are to compensate for the thickness of the gasket between the lower portion of the flywheel housing and the block. Gaskets supplied by the various suppliers are all over the map in thickness.

My thinking is that the gasket thickness should e around .015 in thickness and it will crush down to match up with the .010 shims at the ears. That is why I cut my own out of .015 gasket stock. Ford service bulletins say that the run out for the flywheel housing should be within .006. This is only necessary for the top 180 of the housing as the lower 180 will be pulled into alignment by the bell housing. To make this check with a dial indicator the two bolts for the throttle linkage should be temporarily substituted with shorter bolts and the bolts torqued down to match the four lower ones.

The first thing I would do is check to see if the .010 shims are actually installed behind the ears of the flywheel housing. If they are not there they can easily be installed by loosening the throttle linkage bolts and with a crow bar pry the housing back and slip the shims into place. Bratton's carry them.

These shims can easily fall out when you go to install the engine and\or remove the throttle linkage bolts. I have also seen engines come from a well know engine builder with these shims not installed.

Tom Endy
 
And yes, it could be a worn 2nd gear - or possibly the mating cluster gear which has the matching input to the 2nd gear.

2nd gear is unusual in that it's action/movement is "shared" between 2nd and 3rd gearshift positions. (Think to how you push the gearshift lever to the right and up for 2nd gear and right and down for 3rd gear) 3rd gear is pushing the gear "forward" to match the teeth in the input shaft and 2nd gear is pushing the gear "back" to interface with the smallest end of the cluster gear. Less teeth results in more tooth pressure per teeth and less teeth overall to spread the wear out over. Thus 2nd gear is among those most likely to wear "just on account."

If I had to predict it, I would guess you have a problem with your cluster gear - assuming all the other detent/rail remedies don't solve your issue. It is the smaller of the two mating gears. Stiffer detent/shifter rail action just give you more "margin" against inadvertent slipping out of gear. Given a nearly perfect 2nd/Idler mating, there should be no side thrust tending to put the gears out of match - the detent/shifter rails/clevises only give a modest detention force even in the best of their condition.

So yes, you may be looking at a rebuild.

Joe K
 
Bottom line seems to be to rebuild the transmission and if the gears show wearing (rounded) then replace them. If you are going through the trouble to remove the transmission just re-do it all.
 
The gears have a bevel on the end of each tooth to ease engagement, but look carefully at the sides of each tooth on the gear. The sides should run dead parallel and not with a slight taper. In other words, look at the overall length of each tooth to be sure they are the same thickness on each end, not counting the small bevel on the engagement end.
 
BILL WILLIAMSON said:
Many times, I've seen the problem solved by NEW shift rails, detent plungers & springs, in the shift tower.
Bill W.
Click to expand...

And another "trick" one can use is to use a rat-tail file and "deepen" the detent on the shift rail. One may want to confirm "shift-ability" after doing this modification.

Also, the remedy may result in a transmission that makes noise as the gear may run on the shifter fork continually while attempting to slip out of gear.

For 1st or second gear it may not be problematical as most of us don't drive for long periods in these gears. For third gear the remedy might become annoying.

Joe K
 
Tom Endy said:
Misalignment between the flywheel and the transmission can cause it to jump out of gear. The alignment of the flywheel housing and the back of the engine block is a factor. There are supposed to be horseshoe shape .010 metal shims located between the two ears of the flywheel housing and the engine block where the throttle linkage bolts. These shims are to compensate for the thickness of the gasket between the lower portion of the flywheel housing and the block. Gaskets supplied by the various suppliers are all over the map in thickness.

My thinking is that the gasket thickness should e around .015 in thickness and it will crush down to match up with the .010 shims at the ears. That is why I cut my own out of .015 gasket stock. Ford service bulletins say that the run out for the flywheel housing should be within .006. This is only necessary for the top 180 of the housing as the lower 180 will be pulled into alignment by the bell housing. To make this check with a dial indicator the two bolts for the throttle linkage should be temporarily substituted with shorter bolts and the bolts torqued down to match the four lower ones.

The first thing I would do is check to see if the .010 shims are actually installed behind the ears of the flywheel housing. If they are not there they can easily be installed by loosening the throttle linkage bolts and with a crow bar pry the housing back and slip the shims into place. Bratton's carry them.

These shims can easily fall out when you go to install the engine and\or remove the throttle linkage bolts. I have also seen engines come from a well know engine builder with these shims not installed.

Tom Endy
Click to expand...

Hi, i am new here in this forum and i have the same problem with the second gear, the shims are missing! How can i get the housing back? I loosening the screws already but there is no way to move the housing. What can i do??
Sorry for my not so perfect English, i am from Austria!
Thanks for the help!
 
Yes, as Dennis said pry the top ears back just enough to slip the brass shims in place. I use a large flat tip screwdriver. I like to put a bit of grease on the shims so they stay where you put them during installation. It's no fun if they keep falling down out of sight, or drop to the floor.
 
Thanks for the answers, there are one the two screws to loosen?? I did it already but i cant get the hosing back it dont move. How much pressure can i take? Is it dangerous to disturbe the housing?
Regards Karl
 
NOT to be NEGATIVE, but on an engine that has been run for a long time, I always wonder if adding the housing shims ever causes a leak, where the housing gasket surrounds the open back end of the camshaft? I saw one guy that machined the rear of the cam shorter & machined a plug, with an "O" ring, to seal the rear of the cam!
Bill W.
 
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Maybe you are right! I know from the resatauration documents of the car that the engine was overhauled 35 years ago, the gear only jump out under pressure uphil, i know it now and hold it a little bit so nothing happens.
It seams to let it like it is?
 
will the missing shims affect slippage in all gears on just in second? Just rebuilt tower and still same problem. May well be worn second gear.
 
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