Jumping out of 3rd gear

Mighty1924

Mighty1924

Junior Member
This has me lost.
This spring I installed a complete rebuilt engine and while doing that with the help of a friend we rebuilt the transmission and shifting tower.
Have driven the car about 800 miles since the work was completed.
Last Sunday while on a drive going about 53 mph ****** jumped out of 3rd.
Took shift tower off and checked shafts,forks and detent springs. All look good. Also installed new pins in forks while it was apart.
Got back together and took for a drive and jumped out of 3rd 3 times at 50-53 mph .

Two weeks previous to all this we took a 4 day trip to Wisconsin and not one problem on the whole trip.
Any ideas on what I need to look for beyond the transmission itself.
Thanks
Rick S.
 
I wonder if you didn't get some dirt or something between the transmission and bell housing when you put it back together the first time and now it has worn the gears enough to start slipping out of gear.
 
My old transmission use to do this. It started doing it randomly and unexpectedly as well. A Model A friend who owns a transmission shop here in town came over and somehow put a cut into the gear all the way around. It never jumped out of 3rd gear again. It's now in my brothers speedster and works fine... put a 4 speed in my car from the same transmission guy.
 
Jordan, I wish I knew where that "cut" was made. I have done everything recommended and my transmission still jumps out of third gear on compression.
 
He probably relieved the face of the gear on the side where the slider and the stationary come together. The outer perimeter of this gear can contact the largest diameter gear on the cluster gear and prevent full engagement in 3rd position.

This would be between part No. 23 and No. 6 on the Snyder's Antique Auto parts blow-out. (Seen at http://www.snydersantiqueauto.com/uploads/TRANSMISSSIONASSEMBLYEXPLODED-10150.pdf)

The relief narrows the face of the slider gear and MAYBE shortens it's life a little, but it allows the slider to sit closer to No. 6 and possibly past a worn part on either 23 or 6.

Another thing that can cause this is the pilot bearing in the flywheel is shot - or the small shaft stub is worn down. This causes shaft 6 to "wallow" in it's transmission housing bearing. The 6 gear shaft stub should be a press fit into the center of the bearing.

(I have cut down the shaft No. 6 and pressed on a steel bushing as a solution. Or you can knurl the shaft stub.)

Joe K
 
When you rebuilt the engine did you remember to install the two U-shape .010 shims located between the two ears of the clutch housing and the engine block? This is important to match up with the proper thickness of gasket below it. Without them the transmission is not lined up properly. The thickness of gaskets supplied by suppliers is also all over the map. My experience has been a gasket thickness of about .015 matches up when squeezed with the .010 metal shims. If the transmission is not lined up correctly with the clutch and flywheel it can walk out of any gear. It can also lead to premature clutch failure.

It is always prudent to run a dial indicator mounted to the flywheel around the top 180 degrees of the clutch housing before the bell housing is installed. It should be within .006 according to the Ford service bulletins. You don't have to be concerned with the bottom 180 because it hangs free and the bell housing will pull it into alignment. A lot of clutch housings have been warped out of shape by people jacking the front of the engine up with solid rear motor mounts to change a timing gear. The engine can't bend, so something has to give.

A worn nose on the transmission input shaft that fits into the flywheel pilot bearing is another possible cause. Most are found worn. The repair is to machine them down and press a sleeve over them.

Another Ford service bulletin concerning jumping out of gear states that there must be a close tolerance between the main shaft and the two slider gears. Ford insists that anytime you replace any one of the three parts you must replace all three as a matched set. Good luck with that one.

It has been my experience that reproduction transmission gears with word "Argentina" stamped on them won't stay in any gear.

Tom Endy
 
Thanks all for the information and advice.

I think I have some decisions and work ahead of me to evaluate exactly what needs to be done to solve my problem.
Thanks Again
Rick S.
 
A couple of years ago, I purchased a brand new transmission made in Denmark from a popular Model A parts supplier and it jumped out of 3rd gear on compression. Complained, and they exchanged it for another new one. Same thing. Bell housing run out was only .002". New pilot bearing. I havn't bought any parts from them since. I wish I had rebuilt my old one that was noisey but didn't jump out of gear.
 
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