the rear diff behind my 239-Y is a stock 1954 "292".....what gear change is possible for replacement to fit the case and give good performance, looking for a good midrange for stop light takeoff and highway speeds...?
If known, what is a good vender for the replacement parts..
thanks, Ed

 

Your rear axle is a spicer/dana rear end, known now as a Dana 44. I'd recommend removing the rear axle and replacing it with a 1957-1970 F100 rear end. That would be a 9" rear end and the usual ratios in trucks are 3.5, 3.89. Try this article here on FTE. Rear axle article

 

PC's advice is probably the easiest way to go. I cannot recall the "cutoff" figure off hand, but I believe that ratios less than around 3.7 to 1 in the Dana 44 rear end requires a different carrier. For example, I have a carrier that came out of a 1951 or so Ford automatic car (I think) and it has a 3.31 gear set. I bought it for the same reason you are asking your question. But to find the necessary gears, while many cars and light trucks used the Dana 44 axle, they usually have different pinion splines. This leads into a whole 'nother mix and match issue, if the stock differential yoke cannot be used.

I think, in the end, it is just easier to go to the 9" rear end.

The trick to this is getting the spring clamps from a 57 to 60 truck, since these were the only years that used the 9" rear end where the shock mounts are on the spring clamps. In 61 and later, they mount directly to the axle tube. You can use the axle from the later truck, but you need the 57 - 60 clamp to mount the shocks.

And then, of course, you have to have the driveshaft lengthened for the 9"