As it sits right now the drive line on my T will be 6-8 inches long from the centers of the u-joints. How short can you get away with? The tail shaft and differential line up pretty close.
It's completely safe to run a 1" driveshaft, because my Uncle Bubba ran one 500 mph at Indy in 1972. Now, if everyone agrees with me, then Chrysler, Honda, GM. Ford, Mack, PB, KW, Toyota, Mercedes, Audi (fill in the next 100 names here) were completely wrong, for the last 120 years.
Panic, No offense, because I thought the same things too, and my analytical mind knows better, but I have had a 9"drive shaft running around in a customers car for about two years now with no failure. I know that is not too long, but this guy drives the wheels off of this thing. I did everything I could to change that length, but ultimately the customers choice of components dictated where everything had to land. I was very meticulous about setting up the angles correctly, including the drivers weight in the car and fuel load. That's not to say that next week he can call me up and tell me it fell out, but I expected failure to be a quick thing. And yes, I have had the car on a lift and checked it several times since the car hit the road. Just my .02
It works fine, I drove many a mile with a Tee bucket like that. BUT!, the rear end didn't move much. Most of the ride was in the tires. 70 series Mickey Thompsons, aired up to five to nine PSI, never more. The car had a J2, it never would spin or smoke the rears, but there was nothing quicker across an intersection. It would lift the left front wheel about four inches in first and second. Fun car.
KRAMER...I've seen the trans. yoke bolted to the pinion yoke! SO i would say never. well you didn't say what the application is. it all depend's on what your building...POP.
BULLSHIT. I have built many 4 link rear engine dragsters with driveshafts 6" long, 3-5-4.5 inches of travel on launch. Never busted a driveshaft, ujoint, talishaft or pinion yoke. Several of these cars are capable of running in the 3s in the 1/8th mile. All on transbrakes.. That dont bustem, not much will.
In 2006 I pulled a '50 Cad & B&M Hydro from a '27 T that had been hooked to a buggy sprung '55 Chevy rear by a 10" long (chromed) driveshaft since 1968. The car wasnt driven daily, but it was driven a lot during those 38 years. No failures and the u-joints were flawless!!
Black Swan or not, this exception does, in part, disprove your aforementioned statement: "Conclusion: if the axle moves, the joint will fail very quickly."
Still bullshit. Wont fail, live long and prosper..... An exception would be one car living long with short driveshaft. I've built 15-20 of them. All still racing, some as many as 12 years, same shaft. Have you ever built a short shaft car? If so tell us how it failed, I and several other answering this thread have FIRST hand knowledge regarding the question. How is it that Need louvers quality work saved someone, and my answer that backs him up is a "black swan?" Have a nice day. I have manners see?
Wow, what a difference of opinion. I have seen many four wheel drive trucks with lift kits that have more angle on the drive line than I will ever have. And then that would only be when I hit a pot hole. I know there are thousands of t-buckets with short drive lines, but mine looked shorter than what I have seen, and that is why I asked. As I plan on redoing the engine mounts anyway because I don't like them, so was thinking of moving the engine forward some. I would prefer not to as my body needs to be were it is to look right. The engine then would be to far forward of the firewall, in my opinion.
Kramer, You ask an important and tough to discern (a sound answer) question. Remember that some mis-align (say 3 degrees) helps the u-joint needles re-lube...and that's good! Now, if I were setting up my own car, I'd want to stack the deck in favor of the joints' lifetime! So: Dead on, in alignment? Sure, as long as the fuel tank is half full, and there's a sand bag or two, resembling the typical "live load". Then have the suspension stiff enough, so that a "full launch" doesn't excede the max "operating" angle you've researched as OK. As to the lube function, any twitch in the shaft's angle will move the grease, and help the wear issue.
I don't see what the problem would be if you line the tailshaft and the pinion up properly. The driveshaft in my roadster is 12" long, it has lots of suspension travel, no problems. Unless you're doing the Baja with it, under most circumstances, it's not going to have enough travel underway to bother. Just my 2 cents... Brian
One of my real world experience's was my dirt modified. severe engine setback, and a driveshaft with 4 1/2 inches of tube between the yokes. soft sprung for maximum roll in the corners, so I'm sure there was alot of travel. ran this setup for years. never failed.
You run the risk of throwing off the proportions of the car if you start moving things around. And for what reason, just because someone says your driveshaft is too short? Build your car the way you minds eye sees it. I seriously doubt you will have any u-joint problems, and you will have the car you want instead of something you wish you had done differently. I understand your concerns, but some times ya just gotta give it a try and see how it works out...IMHO!
Weren't Cheetahs built ujoint-to-ujoint? Not sure what they ran for a rear end. If you really need a driveline that short, just run a Jag IRS. Problem solved.
I think there are a lot of "armchair engineers" here that are spouting off without any firsthand experience. Have you ever studied the lay-out of a rear-engine dragster ? The rear diff couples right up to the tranny. Of course there is little to no movement from the rear suspension... I ran a 8" long driveshaft ( 350 / auto / 9" Ford ) for many many miles without a single problem. I have seen shorter driveshafts that were equally as durable. Just run it and have fun. Worry about more important things like - does your wife`s panties match her bra , etc ...
LOL. On a dragster, there is NO movement. They have solidly mounted rears and solidly mounted motors -- just as described several times in this thread.
There are dragsters out there with 4 link set-up, rare yes. Either way, you can no doubt run a very short driveshaft with success. That`s my point. Time for another beer.
BULLSHIT! I have personally built many 4 link rear engine dragsters, complete with driveshafts. Heres a link to one of em I helped build. http://www.racingperspectives.com/c..._004.jpg&img=&tt=&tfile=tn_BKR6-05-13_004.jpg http://www.racingperspectives.com/c...20.jpg&img=80&tt=&tfile=tn_BKR6-05-13_120.jpg (Thanks Brent!!) I have nothing to do with any of following companies, just showing they do exist. http://www.racetechracecars.com/packages.asp?grp=1&pid=20 http://www.worthymotorsports.com/4link.html http://www.markwilliams.com/chassis.aspx HEY PANIC,, BETTER CALL THESE GUYS AND ASK THEM IF SHORT SHAFT IS OK!!!! http://www.coastchassis.com/item--4-Link-Dragster--pardun1.html http://www.mikeboschassiscraft.com/Dragster4link.htm http://bwracecars.com/clients.htm http://www.mahaffeymotorsports.com/Dragsters.htm I could go on, but the list of chassis builders that make 4 link dragsters is pretty much endless...... All with short driveshafts. They work perfectly fine. On a good launch there is lots of movement, sometimes enough to bottom out the chassis on the track. 3-4" is nothing unusual for a soft powered bracket dragster. End of discussion.
I did a deuce roadster chassis for a customer several years ago and buy the time we got a BBC, turbo 400, Gear Vendors od, cramed in front of a Winters Champ QC we had about a 10 inch driveshaft. He drives the wheels off this car with no problems.
Perhaps not end of discussion. At issue was the shortest possible driveshaft length. That would be ujoint to ujoint. Dragsters that couple the output shaft of the tranny directly to the pinion shaft have solidly mounted everything, and if not, not for long.
dude......... Rear engine dragster for bracket racing can and have been built with a 4 link rear suspension. Read the links. I have built many of them. Some as many as 12 years old. the one in this link>>>>>>>>>>>>>>>>>>> http://www.racingperspectives.com/c...20.jpg&img=80&tt=&tfile=tn_BKR6-05-13_120.jpg is nearly 10 years old, second body....... Its fast too, aproaching 200 mph in the 1/8th. They have driveshafts. U-joints, coilovers, anti-roll bars. Same rear suspension as a Prostocker. Our driveshafts were 6" long. No splined couplers.
Apples and oranges. An 8" shaft on the strip does not equal closely-coupled u-joints on the street. Insisting that point A has merit is potentially confusing the discussion of point B.
6" shaft is short. ask your wife. (Pleased dont get pissed about that, its a joke. My wifes answer would be the same as yours.) I doubt that the shaft he needs for his car will be any shorter. They work fine. Have you built a car that used a short driveshaft? If so tell us how it broke. If you havent used one, then butt out. No offense. Sorry to muddle the thread.
The shortest one that I have installed is 5-3/4", running 1350's. It is yoke to yoke, with the tube there just to give something to weld to. It has been in service since 2006, and has seen 25,000+ miles. It shows no sign of malfunction or misbehavior. It is sees 500 lb.-ft. of torque in a 6000 lb. vehicle, and swings about 6" of travel.
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