The neoprene rear seal was made for 1956 (and later) 235 engines. Not to say rope seals were not still in use during those years. They were but in 1956 the grooves were machined more precisely and prior to that, they weren't. Actually I've seen some 235s into which small pegs were set (into the grooves) presumably to keep the rope seal from moving with rotation of the crankshaft (image attached). There were 6 or 7 little pegs set into holes which had been drilled in this one. The neoprene seals were commonly installed by dealerships or repair shops hoping to stop complaints...often without doing anything to the surface of the crankshaft. You can see the surface of one crankshaft where originally a rope seal was used and later a neoprene seal was installed...and you can see the neoprene seal removed from that same engine and the roughly 1.5mm missing from the lip where the crank had ground it down nicely.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
