I just replaced one for a 54 3100 for a customer. It sounded horrible and would not stay in 1st gear. The first/reverse slider had most of the teeth broken off and the low gear on the cluster was toast as well. I found one from a fellow bolter for a reasonable price. I got a quote from my local gear supplier for almost $800 for the parts to fix it.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine