Jumping out of 3Rd

G

GreatLakes28

Junior Member
This issue has been covered a number of times on this forum. I've read through all posting but have yet come up with a solution. After rebuilding the trans, replacing bearings and carefully inspecting gearing the unit was reassembled. The next rebuild was the shift tower, replacing gear lever, shift fork shafts and of course the plunger / springs. On my second or perhaps it was third or fourth try to find an answer I replaced the 3rd gear sliding gear.....some change but didn't correct the problem. I also added additional washers to increase the tension to the plunger springs. I noticed some difference but the issue is still there. Here's what happens, after driving, sometimes one hundred plus miles I can feel the gear shift wanting to move forward. Once it does that it's only a mater of time before popping out of third. This can happen on level roads, on hills or letting off the gas it will jump out of gear. Any suggestions would be helpful and very much appreciated.
 
Sometimes, excess wear of the thrust washers at each end of the cluster gear and the case can cause this problem.
 
GreatLakes28 said:
This issue has been covered a number of times on this forum. I've read through all posting but have yet come up with a solution. After rebuilding the trans, replacing bearings and carefully inspecting gearing the unit was reassembled. The next rebuild was the shift tower, replacing gear lever, shift fork shafts and of course the plunger / springs. On my second or perhaps it was third or fourth try to find an answer I replaced the 3rd gear sliding gear.....some change but didn't correct the problem. I also added additional washers to increase the tension to the plunger springs. I noticed some difference but the issue is still there. Here's what happens, after driving, sometimes one hundred plus miles I can feel the gear shift wanting to move forward. Once it does that it's only a mater of time before popping out of third. This can happen on level roads, on hills or letting off the gas it will jump out of gear. Any suggestions would be helpful and very much appreciated.
Click to expand...
Is the Ball on shifter lever the proper diameter and Not worn?
 
You replaced the sliding gear, but did you replace the input shaft, as that is what third engages onto. If the sliding gear was worn, there's a high chance the input shaft will also be worn where the sliding gear engages.
 
The flywheel housing has to exactly "perpendicular" to the axis of the engine. If it is not it can "walk" the transmission out of gear in the angular vibration created.

In mounting the bell housing to the engine block, one normally uses a "dial indicator" swung by the center flange of the crankshaft. You measure out to the "cut" in the mating edges of the flywheel housing - yunno - where it "mates" with the next downstream bell housing.

This measure has to be VERY close, otherwise everything built on the flywheel housing exists "out of center" or at angle to the crank.

The adjustment for this is in the "ears" where the flywheel housing mates with the block. You put in brass u-shaped "shims" to build up the mount. Or similarly, you can use a file and "whittle down" the mating surface of the ears. Its unlikely but you might whittle down one and shim the other.

As you leave it, the run-out should be below 0.005, or as small as you can get it.

I have actually taken a swipe or two of mill-******* file to the mating surfaces between block and flywheel housing to try to "improve" the lay of the mating flange using the dial indicator.

Joe K
 
The model A was Fords first attempt at a shiftable 3-speed transmission so it's pretty basic. The low and intermediate gears along with the countrer shaft cluster and reverse idler gear are all spur or straight cut gears. They are a bit noisy but don't have much in the way of thrust due to that. There movement is checked to insure proper tracking of gear sets so they do have thrust washers to keep them in line. The high 1:1 ratio is provided by dogging the intermediate slider gear onto the input shaft. As was previously mentioned, that sliding gear has to be spaced to get maximum engagement of the dogs on to the input gear shaft. That input gear shaft is directly affected by any misalignment of the shaft with the clutch and flywheel. If it has any angular displacement, it puts a side load on that input gear that in turn puts an abnormal load on the dog teeth of the intermediate slider gear and the dog splines on the input gear. I hope this explains it well enough. Worn dog splines or intermediate gear dog internal splines can allow disengagement if they are starting to taper or just wear down too much.

The detent springs in the shift tower were also mentioned. New doesn't always mean correct. The tension and spring rate have to be same as original. People market stuff that isn't always correct even though it fits. Another thing is that roller alignment gear inside the input can wear down and cause excessive movement. The OEM Hyatt bearings were tough as nails but the new stuff is not. Some are better than others but none beat the OEM bearings.
 
Last edited:
I have seen the bearing surface that goes into the pilot bearing worn excessive. This causes the shaft to wiggle. Wiggle causes jumping out of gear.
 
Bigsnapper43 said:
I have seen the bearing surface that goes into the pilot bearing worn excessive. This causes the shaft to wiggle. Wiggle causes jumping out of gear.
Click to expand...

I have turned this stub down, made a bushing (drive on fit with loctite blue), turned it after to zero clearance in the bearing, and then knurled it to a drive on fit.

Having a lathe can be SO handy. Are eight lathes MORE handy - or a burden for your wife to dispose of after your passing?

Joe K
 
The service bulletins address the fit of the sliding gears on the output shaft and they need to have very close fit, otherwise in my case, it jumped out of 3rd
 
You must log in or register to reply here.
Back
Top