Difference between single and Dual range Hydramatic

ratlee2

Alright, time to ask a stupid question. How can you tell the difference physically between a single range hydramatic and a dual range hydramatic transmission? Are they both 4-speed transmissions? The reason I ask is I had a transmission rebuilt that was in my dad's garage that came from a Hornet he parted out years ago so I could swap in place of the dual range hydramatic in my car when I got around to pulling the engine. They looked to be the same, but my speedometer is now reading higher than normal. and a quick search on this forum about speedometer gears popped up a comment about single range hydramatics. Being fairly new to Hudsons I now fear that I rebuilt a single range tranmission. What casting numbers should I be looking for on the tranmission.



Thanks,

Rich

[Deleted User]

Go to Ken Cates' Hudson Stepdown pages and you'll find the Hudson Swaps Manual. It's a PDF document, and page 40 has a list of Stepdown Hydromatic codes. D. J. Kava compiled the list, and you could probably track him down thru this forum for more info.

Joe

Park_W

The transmissions are essentially identical except for the valve body change which allowed "dual range" operation. That's merely the ability to select "D3" to keep it from going into 4th gear. Reason: they went to 3.07 with the rear axle ratio, and the Hydramatic got into 4th gear at a fairly low speed. In 4th with the new axle ratio, acceleration at city traffic speeds was pretty poor. The owner manuals suggested running in D3 in city traffic, going to D4 whenever you weren't going to be operating in 20-35 mph conditions. I believe another improvement at the same time was the "part-throttle" kickdown from 4th to 3rd. Earlier types required you to push the gas pedal down pretty far to get down from 4th, so the part-throttle kickdown helped that situation when driving at the lower speeds. You can identify which a tranny is by counting the shift lever detents. Single range units should have 4 (neutral, drive, low, reverse), while the dual range ones have five (neutral, D4, D3, low, reverse).

ratlee2

Thanks guys for not giving me a hard time. I'll hve a few more stupid questions in the future. It should be easy to identify which one it is now. I took the car out for it's maiden voyage yesterday (first time since 1963) and 4th gear would account for its sluggish acceleration. It did seem to shift into high gear real quick. Well, that and I inability to tune those dual carbs. They are kicking my butt even with the carb syncronizer. It idles nicely with the full length Clifford headers and dual exhaust, but bogs down on acceleration. Maybe advancing the timing will help.



Rich

Unknown

to find out which you have pull it down to third at 30 miles per hour if it down shifts smoothly, you have a dual range, if the rear wheels lock up in low gear you have a single range, hold on tto thteering wheel so you dont go thru the windshield, BILL ALBRIGHT

Unknown

Early units used a 3.58 rearend ratio,later 3.07. You may be able to just change the speedo driven gear, remove speedo cable and the adapter it screws into. Count the # of teeth on your old unit compaired to new one. Once the car is in the air only a few minutes to change.. Lou Cote

Unknown

Also check the tag on the right side of the trans case. There will be a letter and two numbers. The numbers are the year of the trans, ie;H52, 51s and early 52s are single range, late 52s and newer are all dual range. Check to see how many positions the shift lever has, the outside one, single range has 4 positions & dual range has 5.

Unknown

Park W wrote:

The transmissions are essentially identical except for the valve body change which allowed "dual range" operation. That's merely the ability to select "D3" to keep it from going into 4th gear. Reason: they went to 3.07 with the rear axle ratio, and the Hydramatic got into 4th gear at a fairly low speed. In 4th with the new axle ratio, acceleration at city traffic speeds was pretty poor. The owner manuals suggested running in D3 in city traffic, going to D4 whenever you weren't going to be operating in 20-35 mph conditions. I believe another improvement at the same time was the "part-throttle" kickdown from 4th to 3rd. Earlier types required you to push the gas pedal down pretty far to get down from 4th, so the part-throttle kickdown helped that situation when driving at the lower speeds. You can identify which a tranny is by counting the shift lever detents. Single range units should have 4 (neutral, drive, low, reverse), while the dual range ones have five (neutral, D4, D3, low, reverse).

Park, are saying that the transmissions are identical except for the valve body. All I need to do on a single range is swap to a dual range valve body?? This almost sounds too simple. Anyone on the forum that has done this?

Unknown

Dual range has a hydralic reverse, the tailshaft housing of the trans is approx. 2" long. single range is mechanical reverse and the tailshaft housing is much shorter maybe 1"??.