RE: A833 OD questions

[ledman_70@xxxxxxxxxxx]

Sorry, I wasn't listening, what did you say?? Just kidding Doug, that 
was a very informative lesson in OD's, thanks. 1 thing I didn't get for 
sure...is the shift pattern reversed for 3rd and 4th, or is it the 
standard pattern? Are you saying the bearing retainer is bigger on the 
OD, so it's necessary to machine the opening in the bell larger to 
accept it? If this is the case, will the bearing retainer from the 
standard 833 interchange? I believe the OD I am getting is from a 
Volare.

Doug Ahern wrote:
> 
> you'd want the truck/van OD unit.  it is b-body length and has the 
> shifter
> provision in the same location as b-bodies.
> 
> the 3/4 gear set is at the front of the 4spd.
> 
> these are constant mesh transmissions..,  all gears are always meshed.
> the only thing that moves or engages are the clutch sleeves that slide
> forward and backward to lock a gear to the mainshaft.
> 
> on a regular 4spd,  3rd gear is engaged when the clutch sleeve goes 
> backward and locks the 3rd gear on the mainshaft to it's counterpart 
> 3rd gear on the lower countershaft.  still on a regular 4spd,  4th gear 
> is engaged when the clutch sleeve moves forward and locks the mainshaft
> to the input shaft. 1:1.  hence "direct drive".  the counter shaft bears 
> no
> load and simply free wheels...  is is why manuals are considered to
> be efficient transmissions.  this where the tranny is 90% of actual
> vehicle operation time.. the only HP drain would be what it takes to
> move the tranny fluid around the box.
> 
> on an OD 4spd,  the 3-4 lever on the outside of the transmission
> is flipped over, so a normal shift pattern from the perceptive of
> the driver and his Hurst 1-2-3-4,  actually shifts the tranny 
> 1-2-4-3.,,  so the driver's 3rd gear is "direct drive" (most 
> efficient) 1:1.  when shifted to the driver's 4th gear, the 833 actually
> engages the traditional 833 3rd gear set by sliding the clutch sleeve
> backward over the the traditional 3rd gear lock.  To make it an OD,
> Chrysler and New Process simply  designed the 3rd gear set to be 
> an overdrive gearset where by the larger tooth count gear was on the
> countershaft and the smaller tooth count gear was on the mainshaft.
> to facilitate the small gear on the mainshaft,  Chrysler and New Process
> used a smaller diameter mainshaft at the 3/4 gear area, hence "OD weak
> spot #1".
> 
> since the tranny spends most of its time in "top gear",  the new OD
> unit would spend most of its time with the countershaft engaged and
> thus, be directing torque through 4 gears and the countershaft 
> instead of a simple direct drive.  to offset the added "side" load
> of the input shafts direction of torque down to the counter shaft
> a larger input bearing was used.   "OD weak spot" averted!  but the
> countershaft is now directing torque for 90% of the driving time,
> and its centering bores in the main case are now under a lot more
> stain.  hence "OD weak spot #2".  this is why Passon's aluminum 
> case bushes this countershaft bore.
> 
> the truck OD to B/RB requires machining a 4spd bellhousing.
> 
> so..,  those are the weaknesses of the OD and how they work.  If
> you are a mild mannered driver,  the OD will stand up.  If you bang
> gears, shread tires all the time, your OD unit will be at its limits.
> 
> If you want a built proof OD unit, you should look at Passon's 
> OD unit.  this is a beast.  its the same basic design that New Process
> and Chrysler used for their OD, but he fixed the weak spots.
> It uses a specially designed OD gear set that uses a regular 
> non-OD mainshaft (not a narrowed mainshaft),  and he bushes the
> main case.  plus he uses an 18 spline input shaft.  
> 
> For my $3K, this is the hot ticket.   Keisler's Tremec 5spd is cool,
> BUT its a rail shifter and it feels like a rail shifter.  the new
> automatic is cool too, but thats an automatic!
> 



Jeff Adams
64 Polara


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