<VV>Overdrive

[FrankCB at aol.com]

Yes, I remember the Borg Warner OD quite  well.  It was on my 1951 Hudson 
Hornet along with a 4.11 rear end, so  the overall ratio was about 2.8 (the OD 
was about 0.7 by  itself).  It was great for cruising with the big Six engine 
that had a 4.75  inch stroke.  I remember driving over 100 mph (indicated) on 
the  Turner Turnpike in OK about 50 years ago (when I was young and  
foolish<GGG>).  The interesting thing about the BW OD was that it  included a "free 
wheeling" operation, so that you could shift without the clutch  provided you did 
it at reasonable speeds and before the overdrive engaged.   It tried to engage 
at 28 mph so I added a switch on the gearshift  that opened the circuit to the 
solenoid so I could shift without the clutch  until I let go of the switch.  
The stock procedure was to floor the  throttle to downshift out of overdrive 
but I could simply press my switch, ease  off the gas and make it downshift 
without full throttle.  The overdrive  also worked in 2nd gear where I used to 
put it when merging onto major  highways.  That way if I really had to 
accelerate at the last instant, I  could simply floor the throttle and the trans would 
immediately downshift from  2nd overdrive to 2nd normal gear with an immediate 
increase in revs and  POWER.
    The BW OD was a planetary gearset unit placed  on the end of the regular 
3 speed trans so it required a shorter driveshaft  to lead back to the 
differential between the rear wheels.  I wish there was  some way to convert one to 
use on the 4 speed (or even the PG) of the  Corvair.  That way the overall 
gearing ratio could drop to a fine  cruising 2.5 overall ratio.  This would drop 
the engine speed at 70  mph to about 2500 rpm instead of the stock 3500 rpm.  
But how to  accomplish this??
    Regards,
    Frank "likes tall gearing"  Burkhard     
 
In a message dated 8/11/2006 8:57:51 AM Eastern Standard Time, pp2 at 6007.us  
writes:

Laycock  de Normanville. Introed in 1948 and used mainly on English cars. In 
the US  the Borg-Warner overdrive was more common (pull a T-handle) postwar  
accessory.  Columbia had a whole series of two-speed rear ends prewar  and 
Hallibrand made their fortune not in wheels but in the "Halibrand  
Quick-Change Rear End" . Most modern I recall was the Hone-O-Matic. All  
wonderful devices but designed for conventional inline  powertrains.

In the 1970s there were a series of articles on how to  adapt a BW O/D to 
the Saginaw gearbox (had to drill one hole). Problem is  they all bolt to 
the output end of the gearbox which is currently bolted  to the  gearbox. To 
add would require an even longer input  shaft,  a special O/D output shaft. 
and some place to put the two  foot longer powertrain.