So, every Hydra-matric was essentially custom-fitted to its engine? I sure learned something today!
What were the real-world consequences of not following this alignment procedure? Vibration? Shortened service life of the transmission?
Not the Hydra-matric transmission itself.
Just the rear main Flywheel Housing and it's Front 3rd half that bolts to the engine block.
Those two flywheel housing pieces were supposed to remain with the engine block that they were dial indicated too.
Pic 1 ,
Pic 2 ,
Pic 3 I don't have a picture of the front housing but it is the far left part in this
Illustration.
Once the housings where aligned to the crankshaft, the bolts were locked down, then the rear housing
was separated from front housing and holes were drilled into the Front housing and engine block.
Dowel pins where driven into the drilled holes to insure the housings stayed aligned.
The idea behind it is blue printing.
As in a drawing on blue paper.
The actual engine and transmission measurements should match the measurements on the blue print.
The GM engineer would draw the engine and transmission on paper.
The engineering drawing indicated a straight line from the front end of
the engine crankshaft all the way to the end of the rear main transmission output shaft.
One straight line front to back.
The break in the straight line is at the engine block to flywheel housing connection.
When the flywheel housings are dial indicated to the crankshaft, it insures that the straight line
continues on all the way to the end of the transmission output shaft. Straight as a arrow.
The straighter the line, front to back, the smoother everything runs.
Lets say the engine block has to be replaced.
The 54 shop manual says to align the bore runout, remove the old dowel pins, dial indicate housing,
drill new larger holes into the front housing & engine block then install oversize dowel pins.
Today instead of using oversize dowel pins you can use offset dowel pins. (no need to drill new larger holes)
There is a screw diver slot to rotate the dowel pin to align the housing.
Some offset dowel pins have a screw diver slot to rotate the dowel pin.
Google offset dowel pin search Some have a Allen wrench set screw.
Video The face runout is usually good, the 54 shop manual says to use shims to align for housing tilt, up and down, side to side squareness to the crankshaft.
That also can be corrected by making sure the front and rear of the housings were machined parallel.
Assuming the back of the engine block is square to the crankshaft.
And making sure the mating surfaces of the engine block and the housings are free from debris.
The consequences of not following this alignment procedure I fear the most is vibration, shake.
Like something is out of balance, a whole truck Shake when auto shifting up or down.
I've heard story's from a couple of people that have replaced engines from Hydramatic trucks.
They couldn't get the truck to run like it did before they put in the new engine.
Me thinks the reason is, is because of misaligned flywheel housings.
A similar check with a dial indicator for the clutch housing is described for manual transmission setups for ADs in the Factory Shop Manual.
Anyone ever do that?
The manual shift transmissions are a little more forgiving.
Unless you are driving at 200 MPH. NASCAR
