<VV> 1960 aluminum three speed transmissions

[BBRT]

Crawford,

Very interesting.  Aftermarket mods to Porsche 901/902 and 915 transaxle 
cases incorporate a large steel section inserted into end of case into which 
the main bearing is fitted. Not sure how countershaft is handled.

Chuck S
Fredericksburg, VA

From: "Crawford Rose" <crawfordrose at msn.com>


>
> All, there was a TSB on this topic from Chevrolet, DR#440, dated June 16, 
> 1960. The rear axle pinioon bearings were faling on Corvairs equipped with 
> 3 speeds.  The countershafts became loose from the fully seated position 
> against the statkes at the front othe transmission case. The countershaft 
> was unable to maintain a light press fit into the bore at the front of the 
> case to prevent rotation and/or fore and aft movement.  When shaft 
> movement occurred, lubricant leaked from the shaft bore and due to the 
> common lube supply for the transaxle the axle oil level became low, 
> causing the pinion bearings to overheat and seize.
>
> The transmissions built after April 28, 1960 have a pin in the shaft to 
> prevent movement of the shaft.
>
> In 1961, the use of cast iron eliminated this looseness problem.  The 1961 
> shop manual discusses the changes in the design from the 1960 design, one 
> of the most interesting being a concentricity face which the 1960 case did 
> not have. This helped center the bore of the concentric mainshaft when the 
> case was mated to the differential pinion nut. Anyway, an aluminum 
> shortage was not the problem as much as aluminum weakness was.  Possibly 
> the April discovery of the cause of the transaxle lubrication failures 
> derailed the four speed until 1961 because the problems with ALL manual 
> transmissions had to be addressed.  The whole transaxle was redesigned and 
> fortunately the four speeds don't have annoying loose countershafts.
>
> Crawford Rose