Jive-Bomber submitted a new blog post: How a Quick Change works in 2 minutes. Continue reading the Original Blog Post
Thanks for posting the video @Jive-Bomber! Glad it was useful. I’m just getting the hang of this video thing...sometime I’ll have to post the outtakes where I get all tongue tied and then invent a few new curse words. Curt
A quick change poking out the rear of hot rod turns it into a serious piece of machinery. The V8 style rears with the early Ford axle bells look just right.
If I understand it correctly, the spur gear turns the pinion gear to drive the ring gear? If so, what ratio is used for the ring and pinion?
Its a curve Curt and you are well along it. Great to see companies take the time to do simple tech videos of their products!
It depends on exactly what rear end it is. The common R&P ratios for the V8 rears are 3.78 and 4.11. The larger Champ units are 4.12 and 4.86 with an occasional 4.57. For a street car, the lowest numerical R&P ratio gives the most practical combinations.
Does having the pinion rotate in the opposite direction change the torque reaction of the rear end to the car?
Hello, Wow, a 3:48 to a 4:11 in several minutes instead of a couple of hours. What a concept for the hot rod community. The Halibrand Quick Change units were available, but for our purposes of racing a stock 1958 348 cubic inch Chevy motor in the factory configuration was not going to happen. The rules were strict. Factory units only. So, for almost every week of our ownership of the 58 Impala, I changed the complete rear end Positraction unit from the stock unit of 4:11 to 4:56 gears on each Thursday night. Then it was ready for any Friday night happenings or definitely ready for the early morning runs at nearby Lion’s Dragstrip. When the all day Saturday event close at night around 10pm, then I had all day Sunday to get those 4:56 gears out in time for Monday-Thursday high school commuting and cruising. When my brother owned the 58 Impala, it was my job to do this rear end gear swap. That was to be compensated for transportation anywhere I wanted to go during this pre-driver’s license time. On Thursday after school and practices, I got to work and was usually finished around 11 pm. Then on Sunday afternoon/night, around 8 pm, I was finished and tired. This went on almost weekly for the driving time. If a very long distance road trip was on the agenda, then we had access to a set of 3.55 gear ratio for the similar swap. Yes, there were times that the 4:56 gears stayed in all week and until the next. The local driving was made for the race prepped powerful set up and with some 7 inch Bruce Slicks, it was Lion’s Dragstrip on the street. Jnaki We always envied those that had the Halibrand units and these days, if we did another hot rod, we would get one of those Winter’s Quick Change units. It took the guy in the film 20 seconds to replace the gears to change the ratios. That would have saved me countless hours of laying on the cold concrete, upside down, installing the complete third member by hand, until we got a Walker Hydraulic Jack to help lift it from a rolling cart to below the rear end installation area. But, it was a learning experience and I learned a lot about axles, gears and mechanics. It was like doing a bench press to get the muscles to function in installing the complete third member in place. Doug Cook doing the same thing in exchanging the rear gear ratio third member or working on his muffler system. But, I have to say, the 58 Impala was up on metal jack stands and not 4x6 inch blocks of wood. It was just the idea of actually jacking up the Impala, removing the axles and then replacing the complete Positraction third member with the new Positraction unit and reverse on Sunday. YRMV A quick change rear end would have been a life saver, even for a sturdy teenage body to quickly asses the needs and exchange/replace the appropriate gears, in record time with relatively little to no stress or straining. YOWZA! The funny thing was that my brother's early art drawings always included a Halibrand Quick Change rear end as it looked a lot better... "We all like a nice rear end !!!"
Rule of thumb for our QCs is 600hp for the smaller V8 rear and 1,000hp for the standard Champ QC. We have a Heavy Duty Champ rear that is for 1,000+ as well as a land speed rear that's even beefier, but that's a different animal in terms of gearing, etc. No, nothing that we've ever noticed or heard of. @jnaki that's a great story. And that's a great photo of Doug Cook...hadn't seen that before.
How much you got? Just a couple of things to consider: With the Big Unit: 10" Ring Gear 12 Bolts Bevel R&P as opposed to hypoid. (Much more efficient) The original rear that these were based on was for 3/4 ton trucks. Horsepower is not really the limiting factor. The combination of Torque, Traction and shock loading will determine the ultimate strength. To me the determination of whether the QC will hold up in a drag car is if the 31 spline axles are sufficient. If you need 35, 40 or more splines you probably can't use a Quickchange.
I'm talking like 300ish horsepower with a 28" street tire and 4.11 gear, will they take normal street abuse? I've never owned one, that's why it made me wonder....
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