specifically the area between where the speedometer driven shaft exits the housing thru a bushing and the rear of the sleeve that the speedometer cable attaches. I looked at a trans from a 28 and that area appears to be the same as the 29-31.

What I'm asking is, a seal that will stop the leak at the driven speedo shaft on a 29-31 will work on what other years.

I've made one that has done the trick on my 31 and would like to make it available to other enthusiasts

Chevrolet

Valve In Head, Ahead In Value