Hello, I can attest to this happening after those long after school hours, then, working on our 1958 Chevy Impala. My brother’s idea was to have a nice 4:11 Positraction rear gears set for his daily high school driving and cruising around. For the street encounters, if any popped up, the 4:11 gears would be just fine. But, in order to be competitive at the Saturday Lion’s Dragstrip competition, we had to have the 4:56 Positraction gear set up in place. Since all cars in our class were relatively the same, the best racers were using 4:56 Positraction gears. The extra cost on the Chevy sedans was approved although not sold in the showroom floor displays or ordering. The extra item had to be purchased over the counter at the Chevy dealer’s parts counter, to qualify. the opening led to the concrete pad before the two car garage. So, my brother crawled under our jack stand, lifted Impala and he showed me all that was necessary to get the wheels, tires, axles off and out. Then drain the oil and ungodly number of nuts to get the whole third member out and replace it with the 4:56 Positraction gears. No, not just the ring and pinion gears. The whole, Positraction third member he had saved enough to buy outright from the local Chevy Dealer’s parts counter. Jnaki At the starting line...1958 But, while I had a whole day of activity of high school classes, I was under the 1958 Impala on Thursday after school to start the procedure of exchanging the 4:11 gears to the 4:56 gear housing. Yes, we did get some ribbing about the gear ratio differences from 4:11 to 4:56 as being “not so much.” That upped our top speed times and also lowered the E.T. down into the 14s from the average 15 second runs. So, yes it did matter for the “little things.” Now, we were in the running for winning the class eliminations… Our stack of trophies proved the naysayers wrong. Every little bit helped us bring home the trophies. It helped that the starting procedure was getting easier to adjust to the "go" signal, too. There were several days that my brother came out to the concrete driveway pad to see what I was doing. He was always inside doing his art, guitar playing and reading magazines, while I was outside doing the exchanges. It was his way to have me “pay for car services” if I needed to go somewhere, basketball practice, games, friend’s houses, etc. And, yes, several times, he found me fast asleep, even on the cold concrete pad, under the Impala on jack stands. Ha! After all of the “extra” work I put into the 58 Impala, the trophies started coming into our realm. Three with cars on top and 3 with Victory statues… The others were already at my brother’s house in Santa Barbara when the later year photo was taken. (All of our hard work, only to be outdone in trophy size by our dad's "largest trout caught on opening day of Lake Crowley" fishing) Note: After I became the official owner of the 58 Impala, the time between 4:11 Positraction changes and the 4:56 gear third member changes slowed down as we left the stock classes. We used the 4:56 Positraction gear third member in the chevy rear axle unit when we built the 40 Willys Coupe. The 4:11 stayed in the 58 Impala for the whole time we built and ran the carburetor SBC motor and then the 671 supercharged version. A fast custom lowered rake direction for the 58 Impala. Thanks, @themoose Even when I had changed the wheel hubs to a Buick bolt pattern for my new direction of Skylark Wire Wheels, it still had the 4:11 Positraction unit in place until there was some action like cruising during Spring Break or hot Summer Nights in and out of the Bixby Knolls area. Then the 4:56 gears went in place to give me the best response to the challenges. YRMV
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