I think on the older 4 spds there is a weep hole so if it is overfilled a little it will drip out of the weep hole could get into the clutch.dont know exactly were the weep hole is. was surfing the web as i was just given a old sm420 with a torque tube universal joint and was looking on a site that shows years i beleave they started using them in 47 to 67. They seemed to be popular with the 4x4,rock crawler.guys for the granny gear and the durability.there was mention of the older ones having a weep hole as one of the guys posting had oil on his clutch s they are often climbing up steep terrain .

1954 Canadian GMC 9300
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