Transmission center & output shafts. Restored or ignored?

[speedytinc]

Thought I would share with you all the restoration of these 2 parts that may be unaddressed during most transmission rebuilds. In working with these 2 parts its apparent that MOST transmissions were/are not in line @ the 4th main creating wear patterns in these parts that need addressing. Weather it be the shafts are not running true from misalignment or side pressures from a bent pan. Commonly evidenced by a loose leaking 4th main.

Tool post grinder working on the output shaft.

The drive plate was degreased & scrubbed clean. NO BEAD BLASTING. Oil plug checked & new bushing fit & bored for the center shaft. Set @ .004" clearance.
The Plate was squared up before the final 4th main shaft surface grind. The plate gets a square/clean up cut to the O.D., lip & mounting face. Just enough for clean up under the 6 mounting holes. Then turned around, double checked on virgin shaft for alignment.

Worn area needing a bit more grind

This part took another .002" to clean 90-95%. Then a quick polish with some 180 emery cloth. The end looks like 100% reground.
The shaft is originally 1.560". The final reground size ended up 1.542" (.018" to square & clean as new.) This plate had more wear than normal. They have typically cleaned up .010" under. A new babbit 4th main is now machined to a .0015-.002" clearance.

In the same fashion, the transmission center shaft is refurbished.
The shaft is degreased & lightly bead blasted.(Stay away from the clutch hub press fit area.) Bearing surfaces get polished in the lathe.
The shaft gets chucked to the 1" 2 bushing section of shaft. The flange gets a clean up grind on its face. Turn around & chuck to the squared up flange. Indicate the 1" 2 bushing shaft virgin shaft to confirm it's mounted to turn true. Grind end to clean that 15/16 dia. end.

2 reground shafts.

Both shafts had been beaten on & needed the mushroom removed & squared up. The one on the left had been filed & had flats on the bearing surface. It took a lot more to clean up & will need a thicker bushing or I'll use it as part of the flywheel balancing shaft..
The one on the right cleaned .006" under. The new bushing just cleaned up enough for that .004" clearance.

Its important that there is very little to no run out @ the output shaft. <.002"
To many people throw a transmission together without checking the output run out. That's costing horsepower excessive wear & strain to the point of a broken crank if off enough.
Start checking. You will be surprised how bad the alignment is. Now you can address it.

[Dan Hatch]

Look at Herm’s post years ago about rebuilding a trans.
He was a master at it. Dan

[Dan McEachern]

And when you get all that done, mount the trans on the crank with out the high gear spring installed and confirm the 4th main journal runout.

[speedytinc]

And when you get all that done, mount the trans on the crank with out the high gear spring installed and confirm the 4th main journal runout.

Dan, why remove the spring? When the output plate & drum are bolted together, the spring should not effect anything. What am I missing? Loose rivets?

My way for mounting the transmission is to mount the flywheel & indicate the runout of the transmission shaft in the vertical position. Checking the shaft high & low looking for out of round &/or a bent crank flange. Always needs work to get squared up. Once in alignment, the transmission gets built/assembled from that point onto the center shaft. When assembled, output plate shaft is checked for no run out. When the 4th main is checked to the pan for fit, if it slides in centered, pan & transmission are in alignment.

[DHort]

We took my engine out to reseal it. With the engine vertical we checked the runout, 0.028 wobble. Thats not good. My car was hit by a cycle a number of years ago. Maybe the force of that hit came ip through the driveshaft??? Had the end of the crankshaft reground and the end of the transmission shaft reground. Put it all back together and now only 0.005 wobble. Installed a new 4 th main and put engine back in car. Now if we could get above 40 degrees I can take it for a ride. Engine sounds good.

[Jerry VanOoteghem]

John,

I also have a Logan lathe. What are you using for a toolpost grinder???

[speedytinc]

John,

I also have a Logan lathe. What are you using for a toolpost grinder???

Its a big Dumore. Swap meet find. I have a smaller one, Atlas.would work well, but the big dumore does the drums easily too.

[Dan Hatch]

Link to Herm post on transmission rebuild
https://mtfca.com/phpBB3/viewtopic.php?t=2114

[speedytinc]

Link to Herm post on transmission rebuild
https://mtfca.com/phpBB3/viewtopic.php?t=2114

Done that again via your suggestion.
Seeing the use of the Wilson reaming fixture was a real turn off on his quality work. WAIT.
Then I read where he bores the bushings & only finishes the last .001" with the reamer. Unnecessary extra step?, but not harmful. I find reamers mostly useless. They cant adjust for shaft wear. Custom boring does. Everything has a degree of wear. Now consider most shafts have .002 wear & the reamer is made for .002 clearance. Makes for an easy .004 clearance.
Herm does a nice job. Detail & measurement oriented.

I used to cut drums with carbide. I prefer grinding on the faces now. Messier, but less harmonic chatter & it replicates the original Ford ground finish.
I have noted & liked his splitting of the band lining to 2 pieces.
I also like his treatment of the 3 finger hold down - better than mine. Going to steal that idea.
Another great day, something new learned.

[Kevin Pharis]

Then I read where he bores the bushings & only finishes the last .001" with the reamer. Unnecessary extra step?, but not harmful.

A reamer will follow the bore it is cutting... even if it’s in the wrong spot! Pre-boring the top of a drilled hole to guide a reamer is common practice when precise location is required. Needed for this application...? Probably not. Just wanted to confirm Herm’s sanity

[speedytinc]

Then I read where he bores the bushings & only finishes the last .001" with the reamer. Unnecessary extra step?, but not harmful.

A reamer will follow the bore it is cutting... even if it’s in the wrong spot! Pre-boring the top of a drilled hole to guide a reamer is common practice when precise location is required. Needed for this application...? Probably not. Just wanted to confirm Herm’s sanity

Yea, I got that. But why not take that last pass, whall set for boring, to finish that last .001? Setting into the fixture to remove that last .001 is extra work for a lower quality hole finish. Boring is cleaner & smoother than reaming. Not faulting him, just dont make sense to me.

[Les Schubert]

Precisely why I invented the “floating transmission shaft “. Also manages the deflection that occurs in the pan while driving.

[Kevin Pharis]

Yea, I got that. But why not take that last pass, whall set for boring, to finish that last .001? Setting into the fixture to remove that last .001 is extra work for a lower quality hole finish. Boring is cleaner & smoother than reaming. Not faulting him, just dont make sense to me.

All good questions! I’m sure he had his opinions... like we all do

[Dan McEachern]

Hi John-I prefer three checks while mounting the trans. I pretty much assemble the trans after mounting the flywheel and main shaft on the crank flange.

First off, with the flywheel and mainshaft assembled to the crank, I check the mainshaft for any runout by rotating the the crank. Then I assemble the trans onto the main shaft. I prefer to check for tail shaft runout two ways- 1) Rotate the drum assembly / tailshaft on the main shaft while checking for runout and 2)rotating the crankshaft / crank. I could bolt the tailshaft into the flywheel and build the trans, but then if I have run out issues after everything is mounted, I don't have any idea where the problem is.

Between the main shaft running true on the mains and the driven plate on the brake drum and all points in-between, any runout is accumulative and adds up very quickly. Prior to al of this, all mating surfaces are checked for run out and corrected where necessary.

Rather than leaving the spring off, you could certainly block up the throw out collar to release the clutch pack. I hope this answers your question.