Guest redman60 Posted February 3, 2006 Share Posted February 3, 2006 I once knew, but I've forgotten. Why can you shift an electric overdirve transmission (long since obsolete) without the clutch.In college, I had a '57 Ford with overdrive. You had to put the clutch in at stoplights, etc. but otherwise--as I recall--it was pretty much like Fluid Drive. You could shift between second and third without the clutch.Help me, I lost the formula. Link to comment Share on other sites More sharing options...
Aanderson44 Posted February 3, 2006 Share Posted February 3, 2006 <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I once knew, but I've forgotten. Why can you shift an electric overdirve transmission (long since obsolete) without the clutch.In college, I had a '57 Ford with overdrive. You had to put the clutch in at stoplights, etc. but otherwise--as I recall--it was pretty much like Fluid Drive. You could shift between second and third without the clutch.Help me, I lost the formula. </div></div>Pretty simple, no formula required actually. Early overdrives were an add-on, not part of the transmission itself. For example, Fords prior to 1949, having torque-tube drivelines, could only be fitted (unless you wanted to pay out a lot of money to have the torque tube and driveshaft shortened!) with an overdrive unit in the rear axle itself, the Columbia unit, which required only the replacing of one side of the rear axle housing to install. Overdrives used with the more widely used "Hotchkiss" driveshaft system (two universal joints and an open driveshaft) got their overdrive units as add-on's replacing the standard tail shaft of the transmission and its housing. Thus, those early overdives were controlled separately from the normal 3-speed gearbox transmissions. Starting in the late 1970's, however, the 5-speed manual transmissions began coming, with 5th gear being an overdrive, as well as 4-speed automatics, with 4th gear being overdrive, and that's pretty much what we see today.Art Link to comment Share on other sites More sharing options...
Guest Posted February 3, 2006 Share Posted February 3, 2006 did they put a two speed rear end in like a truck? Link to comment Share on other sites More sharing options...
The Old Guy Posted February 3, 2006 Share Posted February 3, 2006 Overdrive allowed free wheeling until the overdrive was engaged. this left the trans in a no load condition that let the synchronizers do their job and stop the gears Link to comment Share on other sites More sharing options...
R W Burgess Posted February 3, 2006 Share Posted February 3, 2006 I'll give this a "Star" old man. I'm 58 and grew up on the farm. The old farm trucks had a vacuum operated two speed rear, which would do a lot of free wheeling unless you hit the gas hard to engauge. Did the autos operate the same way?Somewhere around the late 50's, I think, the trucking industry went to the electric two speed rear, which we still have today in the small truck(1-2 ton) catagory. Wayne Link to comment Share on other sites More sharing options...
The Old Guy Posted February 3, 2006 Share Posted February 3, 2006 The Ford and Chev overdrives had a planetary gear set that was engaged by electric solenoid.The solenoid was activated by a centrigugal switch that kicked in around 28-30 MPH. Until thenthe trans had no positive connection to the rear axle.PS I am 72 and have played with this "stuff" forever Link to comment Share on other sites More sharing options...
Guest De Soto Frank Posted February 6, 2006 Share Posted February 6, 2006 RE: OD trannys...I always thought they "freewheeled" AFTER they had up-shifted into OD ?At any rate, they did have a free-wheeling function somewhere in there...that would explain being able to change gears with the column shift and not use the clutch.Two=Speed rears - There were aftermarket rears for Fords/Lincolns to provide different final-drive ratios: the Ruxstell hi-speed rear for the Model T, and Columbia 2-speed rears for the later Fords, 'till the end of Torque-tube ('48).Chevy certainly would've benefitted from some sort of OD or 2-speed rear, but I'm not aware of any that were available during Chevy's torque-tube days (through 1954)...Chevy didn't offer OD until 1955, and by then they had the small-block, and a better six, and OD wasn't so critical...As for 2-speeds in Trucks, that was for more pulling power...at least where Chevies were concerned...the 2-speed rears offered a "lower" pulling gear for the "low-range"...the "high-range" was no higher than the ratio in the single-speed big truck rear (6.17, I believe)...Two speed-rears didn't make the big iron go any faster...just meant you could haul more payload with that Stovebolt six... Link to comment Share on other sites More sharing options...
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