I just learned of these and was surprised there aren't any threads here. I'd posted another thread about my first experience in the 1/8 and the poor performance of my car due to slow launches with 2.93 gears and a VP converter. My first thought to improve launch was a Ford 9" with steep gears and a Gear Vendors overdrive to keep it highway friendly. The obvious cons are you're still limited to the one set of gears (without major work to change them) and the GV unit is expensive and a pain to install. A guy told me about quick change rears....simply remove the back diff cover and swap out two spur gears. 10 minutes tops. Drive your car to the track using your highway gears, swap them out for racing and you're launching like a real race car. These are the norm in circle track racing and apparently have been used quite a bit even in drag racing and street rods. Has anyone installed one in a GS? There must be some major downside I haven't run across yet or everyone would be using them. I've got plenty of room in my '67 between the diff and gas tank. Seems like a no brainer?
These are everywhere in the circle track world. It's a neat idea but they are not suited for street driving or drag racing. The straight cut gears would drive you nuts on the street. They would scream. These rears are not rugged enough for the loads a drag car or even a hot street car would put on them. They would puke on a good launch. Circle track guys don't load the drivetrain as hard as we do and the cars weigh 2k less.
I talked to reps at both Winters and Tiger and both cautioned against a quick change for drag racing, even at my relatively low hp. They said the ring and pinion would be fine but the pinion tries to push the spur gears out the back on launch. Still not completely dissuaded, I started measuring and there just isn't the room for suspension travel with a quick change in a '67. Too bad it won't work cause its a great idea. Back to the drawing board with a traditional rear diff...
You could use a Ford 9in and have two carrier setups....with an impact it doesn't take long to swap out. Cheaper than gear vendors.
410 sprint cars make over 900 hp but I don't know how to equate the loading of a sprint car to the initial launch of a 600 hp dragster. They make different sizes of quick changes, the biggest has a 10" ring gear with 31 spline axles. Hard to believe that wouldn't handle drag racing.
My uncle made a cool quick change setup back in the day. Put your highway gears and and drive your stuff to the strip, then put int the best gearing for conditions.
Ya there are plenty of guys testifying that they've used QC rears for drag racing for years without problems, and other say they tried it once and grenaded the thing. To each his own, but given the cost it would be a heartbreaker to have one explode the first time out.
Now that's what I'm talkin' about!! Do you know whatever happened to this idea? It appears a few were produced but they never became mainstream? Seems like a great idea with lots of benefits...keep your existing rear, it wouldn't change your pinion angle, etc. Wonder why it never caught on, too much rotating mass on the driveline?
The sprint cars also weigh 2000 lbs soaking wet. Which is why they are bad to the bone. HorsepowerxWeight= stress. Every quick change rear I've seen has been under a circle track car. The wheel bolt pattern is huge- the lugs are practically in the rim shell. Also they have quite a booty hanging off them in that quick change housing. I would think that would interfere with a stock fuel tank.?
The cost of the Quick Change put it out of reach of most "weekend warriors" as well as a cut down drive shaft. While the added mass would be a hit, the ability to "dial in a gear" for conditions would have made the trade off worth it in the hands of someone who could math it out. His CS2 Hi/Lo just gained more of a following, then folks started mating LENCOs together to get 3/4/5 speeds and never looked back. Train Kept A Rollin'...
They come in whatever lug pattern you want. The wide five lug pattern you are referring to are popular among regional late model asphalt series, dirt modified and dirt late models cars. They make them for independent rear suspension applications too. My sprint cars only have one lug nut and the weigh 1,400 pounds. There was a time when World of Outlaw cars were getting under 1,000, they changed that due to safety concerns. I've seen dirt cars twist drive shafts, break yokes and not hurt the quick change rear.
