[Healeys] Gearbox Problem

[bspidell at comcast.net (Bob Spidell)]

My gearbox is popping out of 4th and 4th/OD, usually coasting in gear 
downhill, but sometimes randomly.  Anyone know what the typical cause(s) 
of this are?

My guess?  My rebuilt engine has (much) more compression, and the 
'reverse torque' from coasting it causing something to flex or buckle in 
the box.

TIA,

Bob