I'm stumped. Any Transmission guys here?

[Darren J]

Hey guys I need more advice. 1926 Coupe here.

Problem:

So I have new triple gear bushings with 10 Thousands thrust.
The driven gear is pressed flush with the brake drum shaft.
New transmission shaft from Lang's.
Trans shaft installed as far as it will go and torqued to spec.
When I took it apart it had the three thrust washers for the clutch drum.

Putting it all back together:

You can see from the pics that the bottom of the clutch drum key is basically flush with the drum. If I were to install the new three thrust washers, from Lang's which measure .130, I don't have clearance for the key. The only way the clutch key fits is to not use the three thrust washers as stated in the mtfca transmission book.

I'm stumped, any ideas on what's going on?

Thanks in advance, Darren

[speedytinc]

READ YOUR SERVICE MANUAL. You missed a step. Driven gear is not flush. Once You get it flush, you check the clearance between the driven gear & low drum gear. Continue pressing until you reach the clearance spec. (never had one fit flush)
The driven gear shaft bushing must be installed deep enough to fully clear the base of the center shaft's large radius. The edge of the driven gear shaft rests on the base flange of the center shaft.
Other possibilities: Transmission bushings must be pressed in just past flush to assure clearance with the drum that it mates into. Your shown bushing doesn't look in past flush. (May be an optical delusion?)
I ONLY use original parts. I could not say there is not an error in the new repop center shaft. I suspect if there was we would have heard about it here, since some people do use new center shafts. It has happened with new axle shafts regarding key cut location/depth.

Regarding your triple gear bushings: Pin clearance should be min. .004-.005. The ID of the flange should have a large chamfer & ramped into the oil grooves.
These bushings are most vulnerable to a lack of lubrication. In low & reverse & neutral they are spinning very fast. Very failure prone.

[Darren J]

Service manual page 81 Paragraph 300 says to press the driven gear down until flush with the face of the brake drum shaft. The clearance between driven gear and slow speed gears should be .006.

In order to check that clearance I assume I have to put the trans with the triple gears on the flywheel right?

Thanks, Darren

[speedytinc]

Service manual page 81 Paragraph 300 says to press the driven gear down until flush with the face of the brake drum shaft. The clearance between driven gear and slow speed gears should be .006.

In order to check that clearance I assume I have to put the trans with the triple gears on the flywheel right?

Thanks, Darren

No. Before mounting the drum pack.
When you press on the driven gear, (holding the drum pack together) You use your feeler gauge between the low drum gear & the driven gear.
I think there is a fig. xx showing this. Next step is to mount the triple gears on the drum pack & place over the center shaft & 3 pins.

Backing up a few steps: When you bolt the flywheel & center shaft to the crank flange, you need to indicate the center shaft for run-out.
.002" or less. This is a good way to find a crank flange hole pattern is off or out of square. Run out is one of the reasons for crank breaks.

[Scott_Conger]

Brake drum bushing closest to the tail shaft flange is not deep enough - the radius of the shaft is hitting the bushing and is holding the entire stack of drums up and makes the shaft appear to be too short...exactly like you are experiencing.

Also, if you have bushed the triple gears, you really really really really must do a lot of study regarding the fit of the bushing to the pins. Too close of a fit to the pins and you run a very real risk of seizing a bushing to a pin

This is a long read, but full of good information regarding triple gear bushings, and the explanation of what FORD's drawings meant and how they should be interpreted: viewtopic.php?t=6599

[RGould1910]

God bless those who can consistently achieve .002" runout on the transmission shaft. I strive for. 002" but will reluctantly accept .006" if I can't get it closer. Switching orientation and careful machining of the crank and transmission shaft flanges won't insure a perfect outcome.
A popular rebuilder I know accepts a .001 to .0015" runout on the trans shaft flange That translates to a .003 to .0045" runout where the shaft enters the driving plate even if there is zero runout on the crank flange and the hotizontal alignment of the two is perfect.

[speedytinc]

God bless those who can consistently achieve .002" runout on the transmission shaft. I strive for. 002" but will reluctantly accept .006" if I can't get it closer. Switching orientation and careful machining of the crank and transmission shaft flanges won't insure a perfect outcome.
A popular rebuilder I know accepts a .001 to .0015" runout on the trans shaft flange That translates to a .003 to .0045" runout where the shaft enters the driving plate even if there is zero runout on the crank flange and the hotizontal alignment of the two is perfect.

.006 is more than bushing clearances. The drum pack will wiggle. Not optimal. .003 would be kind of acceptable.
If the center shaft flange runs out any on its own, it can be ground to Zero run out.(tool post grinder)
Then you only have to deal with the crank flange.

[Dan Hatch]

Find Herm’s thread on how he did transmissions.
If you used the standard vendor triple gear pins and didn’t polish them, you may have problems.

[Dan McEachern]

Double check what Scott wrote above- most likely the main shaft bushing is not pressed far enough into the housing on the driven gear end. A little too far in is better than not enough. Remember to check for correct main shaft end play after your clutch hub is installed.

[Darren J]

Thanks guys for all the advice I’ll keep on it

Darren