3rd Gear

[nosbod]

Hello,
Last month my gearbox cried enough so out it came and was rebuilt with all new internals. It was re installed and woks perfectly except that 3rd does not feel to fully engage and jumps out on over run. I swapped the tower for one that has given no trouble before so eliminating as a cause of the problem.
Does this mean as I fear that I must remove the box and disassemble it again or do any of you wise ones out there know differently?
Yours in expectation
John

[Will N]

I would take a closer look at the shift tower before ripping into the tranny. It may have worked before because the tranny was worn and loose and the high gear engaged with little effort. But the new gears with less clearance than the old worn ones likely need a firmer, longer shove to fully engage. Look at the ball on the end of the shifter lever. Is it worn? Look at the notches on the shifter forks that the ball fits into. Are the notches worn? Look at the face of the shifter forks that engage the slot in the gears. Are they worn? Any wear would decrease the motion of the shift forks leading to the gears not fully engaging.

[nosbod]

Many thanks Will. The gear lever has been replaced so the ball is ok but I will certainly check the selector forks and slots the ball engages more closely and hope!

[Joe K]

or do any of you wise ones out there know differently?

Gosh. Flattery.

A common reason for creeping out of 3rd is a bad pilot bearing in the flywheel. A bad pilot will "oscillate" the input shaft to the tranny causing the 3rd/2nd gear to walk off the 3rd position.

Do you have the front shield on the front main bearing in the transmission oriented correctly on the shaft? If placed reversed it might cause the input shaft/bearing of the tranny to be too far 'forward' resulting in a tendency to pop out of 3rd gear.

See part 7 on Snyder's tranny diagram. http://www.snydersantiqueauto.com/up...ODED-10150.pdf

Check your tower to be sure you have the "indents" clean on the 2/3 detent rail clean and that the spring detent can reach fully into the indent and hold it when you are in 3rd. (this can be done by removal of the tower to the work-bench.)

While tower out, you can mark the detent rail somehow to indicate the "detented" position of the slider rail when in 3rd. Normally seen on the "front" surface of the shift tower when removed?

Then, with the tranny assembled, try to repeat the same test and verify the rail is "fully detented" when in 3rd gear. You may be able to look in the viewport of the bell housing and with a mirror see the same front surface of the tranny and bellhousing holes which allow one to where the detent rails are. The driver side detent rail is the one to look at. (lever right - movement of left shift fork/left detent rail.

You're looking to verify if a "mis-match" exists between full detent position and full 3rd gear position.

With modern parts such a condition may be possible through error of manufacture. You haven't mentioned if you replaced the detent rails or re-worked your shifter forks. If so you might try comparing these parts to an original part?

Reaching a little bit on this last to achieve a diagnosis? Or means to get it?

Joe K

[Gold Digger]

If the shifter feels like it's not engaging all the way it sounds like there is trouble in the shifter, but also I've seen a peace of dirt or grease get stuck on the mating surfaces of the transmission and bell housing and cause the vehicle to jump out of gear by being misaligned. The pilot bearing mentioned by Joe K needs to be checked out.

[Dick M]

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I would also check the shifting rails (detent shafts) for wear and/or slop as they pass through the bushings of the shift tower. Either the shifting rails, or the bushings, or both can wear over time and become sloppy. I would also check the shifting forks for excessive wear where the ball for the shifter engages. A loose fit can cause problems. Further, I would check for a weak spring between the detent balls. I would replace anything looks worn or weak. It is easier to check and replace what is mentioned in this thread than to pull the tranny. JMO

[Tom Wesenberg]

Measure the distance from the front of the shift fork to the rear of the gasket surface on the front side of the cover. You'll have to use a square to get this distance. Then slide the 2-3 gear forward to full engagement and measure the shift fork groove distance to the rear edge of the gasket surface on the front of the case. They should be equal. I don't have a picture, but if you need a better description, just ask. Remember the shift lever moves LESS distance from neutral to third than it does for any other gear.

[1931 flamingo]

You say all new internals. US gears or the "Danish" ones?? Or new (used) to your transmission??
Paul in CT

[larrys40]

As Tom indicated realize that the throw to 3rd is shorter than 1st or 2nd, as it is just moving the second/high slider forward to engage with the main input shaft splines.
My guess is that the problem is in the shift tower ( forks worn/bent, springs/detent worn) or shift lever. The ball must be trued round and fit properly within the fork assembly.
Just because you swapped assemblies doesn't mean that they both couldn't have issues.

I doubt your pilot is bad..... I would check all of the above first, If you hear noise from the pilot you can always pull the rear back, remove the u-joint and rear trans retainer and sliders along with main drive gear shaft out the back of the trans, and depress clutch and spin input shaft and feel for roughness/fore/aft movement. If the bearing retainer were on wront it would probably be making a scraping noise.....

Let us know what you find.
Thanks,
Larry Shepard

[Tom Endy]

If the two .010 thick horseshoe shaped shims are missing from behind the two ears of the flywheel housing where the throttle linkage bolts on it can throw off the alignment of the trans and clutch and cause the trans to walk out of gear.

Reproduction gears are always suspect. Depending on where they came from or who made them may be the cause. If the word "Argentina" is stamped on them they are likely not to stay in any gear.

Tom Endy

[Joe K]

Originally Posted by Tom Wesenberg

Measure the distance from the front of the shift fork to the rear of the gasket surface on the front side of the cover. You'll have to use a square to get this distance. Then slide the 2-3 gear forward to full engagement and measure the shift fork groove distance to the rear edge of the gasket surface on the front of the case. They should be equal. I don't have a picture, but if you need a better description, just ask. Remember the shift lever moves LESS distance from neutral to third than it does for any other gear.

I like Tom W's methodology of establishing the "detent point" and comparing it to the "3rd point" rather than my "external" method given in post 4.

And Tom E's description of the function of the two "ears" is correct. Additional shims can be added to make the case edge within 0.005. Somewhere in one of the books is described a "sweep arm" used with a dial indicator to determine distortion as you use and turn the crankshaft as a center.

Joe K

[pat in Santa Cruz]

Have you determined if the new 2nd/3rd slider will mate up to the drive gear teeth? With the top off, see if you can move the 2nd/3rd slider fully onto the main drive gear. If you can, suspect the shifting mechanism. If you cannot, the problem is with the mating of the third gear.

[Tom Wesenberg]

This isn't likely to help, but just for kicks here is a picture of the cutaway tranny in the Model A museum at Gilmore.

[Will N]

That cutaway tranny is in high gear, FYI.

[George Miller]

Tom
If you don;t mind I would like to use that cutout for my transmission class in a few days.

[Tom Wesenberg]

Originally Posted by George Miller

Tom
If you don;t mind I would like to use that cutout for my transmission class in a few days.

Have at it!

[Roger V]

I might have missed it in the above posts, but often times the detent "bullets" are badly worn and will not stay in the detent even with a good spring. I've had some I took out of a used and obviously well worn trans that were nearly flat.

[Brian T]

He as already established that the problem is not in the shift tower, and no mention that the problem existed prior, I would be looking that defective parts were replaced , we do know about the junk gears that are imported.
We do not know if they are new parts, or used parts that are new to the transmission, a poorly fitting 2nd-3rd gear or main shaft comes to mind, I have repaired similar problems on new cars during the warranty period, generally mis-machined parts.

[nosbod]

Well I knew I wouldn't be disappointed and am very grateful for the informative responses. All the parts used were quality US products and the pilot bearing is in good order as well. It seems that I will follow the advice of Tom and others and pay attention to the tower and check thoroughly for any lost movement causing 3rd not to be selected properly as that seems to be the most likely source of the problem.I will let you know what transpires.
Many thanks.
John