The Stovebolt Site Forums The Shop Area Driveline Hydra-Matic transmission

I have a 1954 chevy 3100. The truck is a 235 equipped with the hydra-matic trans. I was told by a gentlemen that the gear ratio was different then trucks with the standard transmission. Is this true? Thanks

MFW

The final drive (4th speed) gear ratio is the same as the 3-speed and the 4-speed manual transmissions: 1:1 in high gear

The ratios of gears 1-4 are different between the H-M and the 4-speed manual transmission.

Reverse gear ratios are different in all the transmissions.

1954 truck manual transmission ratios (forward and reverse)
1954 truck Hydra-Matic transmission ratios (forward and reverse)

Ok,cool thanks. What about the rear end? Same as standard ?

MFW

The H-M rear end ratio is 3.90:1 , as used in other 1954 1/2 ton trucks.

HOWEVER: the H-M torque-tube is a shorter length - so, the H-M rear-end is NOT interchangeable with the manual tranmissions' rear torque-tube.

H-M and Manual trans. torque tube measurements.
Torque tube length and how to measure.

Torque tube length
1948-54 Manual trans. 60 1/8" , 3 and 4 speed tranny's
1954---- H-M trans.....53 7/8"

Propeller shafts are different lengths. Type C
1948-54 Manual trans. 63 7/8"
1954---- H-M trans. 57 5/8"
Splines are the same on both. 17
SOURCE

I think that is the only difference between the H-M and Manual trans. torque tubes

That is correct.

We converted a 1954 3100 H-M rear-end to 3.55 Ring & Pinion, using the standard installation/seal/bushing kit.