How short can a driveshaft be?

I want to put a 303 Olds with a Lasalle tranny into my 27 T sedan. I have been doing some really rough measuring and it looks like the driveshaft will be kinda short. Anyone here use this combo in a T before? Is there a minimum length for driveshafts?

If it ends up being too short, does anyone have links to anything showing how to shorten a Lasalle tranny? I'm told it can be done, but how much trouble is it?

Thanks.

 

The driveshaft in my bucket is 9" center to center on the joints. You just have to make sure everything is lined up pretty good.

 

Driveshaft? what driveshaft? My T has barely nothing there. I would have to measure, but I'll bet it is less than 6 inches long. It is kind of cute. Might as well not even have one but the Dodge have that funky joint so you can't bolt it together with only one u-joint.

 

The Lasalle trans in my Lyndwood rail has the tailshaft removed and a Ford V8 coupler adapted to it and that bolts directly to the ford flathead rear, NO driveshaft.

 

I helped build a Cobra replica that had around an 12" driveshaft. The original Cheetah sportscars had no diveshaft at all, just U-joint. Whatever fits.

 

It's my understanding that two U-joints are required, but I have seen one U-joint used in a drag racing application.

I believe it was in the Danny Ongais Corvair Funny.
Serious engine setback in that one.

 

i dont think length is an issue. if you don't use 2 joints it will cause a vibration .make sure the joints are in phase and your working angles are not greater than 5 or so degrees and youll be ok.

 

U-joints do a number of things but mainly are there b/c of misalignment. Carriers are not centered in the diff. But really is what they do is allow the diff to move up and down. on a car I built with a solid rear axel {SC V6 & AOD rear engine} there was only a yolk with one u-joint connected to the diff. Of course it was solid and all.
Just check that the total rear end movement up and down plus the offset between the trans/diff does not bind any u-joints and you will be ok.

 

Right as usual, C9. My mistake.

 

It's gotta be longer than the possible travel of the rear end.. unless it's got IRS.
The mentioned Cheetah had IRS with the differential pumpkin bolted as solid to the frame as the engine.
I think if I got into a way short driveshaft I'd be checking out the array of IFS//FWD CV jointed drive axles available today for a ready made or at least adaptable alternative.

 

In my T-Bucket the drive shaft is 9 1/4" long from U-Joint to U-Joint. But I do know of another T-Bucket that has a drive shaft of about 6".

 

My bucket runs a 5 speed/Flathead combo w/ a Banjo. All the adaptors and whatnot didn't make for a long shaft. Joint to joint, mine is about 3 1/2 inches. Just gotta watch the jumps is all so it doesn't bind.

 

You must be talking 3-1/2" of tube. I had a couple 6" driveshafts made for Jag axles and there is about 2" of tube between joints. I don't know if they will work yet.

 

No, 3" total center to center of joints. It's short....too short.

 

Thanks guys.

Will the yoke in the tranny move enough back and forth? It is supposed to move as the suspension moves up and down, right?

 

think about it. a 7000hp fueler runs 337+mph with no driveshaft.

 

Just thinking out loud here.....

Seems to me that the SHORTER you make your driveshaft - means you're probably gonna want to ALSO limit your rear end travel - to prevent the driveshaft angle from getting to radical during suspension travel. Could get ugly.

Multiple Ujoints are only really needed IF you have misalignments - If everything was INLINE (not parallel, but INLINE) then there'd be no reason why a single Ujoint couldn't be used - or none at all - this assumes a SOLID mounted rear axle of course.

A single Ujoint with input/output shafts operating at an angle to one another adds up to a variable change in velocity during rotation which spells vibration.

How short is too short?? Like anything - if you acknowedge to certain factors and design for them you can bend the rules.

 

you might wanna think about using a caddilac style c/v joint--not the type used in f.w.d. applications--the rear of the drivesfaft has a coupler with two u-joints in it (broncos from the 90's also have them)--your pinion angle can be severly out of whack and it still wont vibrate. if it wasnt cold and dark outside, I would go measure mine to give you an idea how long it is by istelf, then you could see if it was possible.

after dealing with one particular vehicles driveshaft woes, EVERYTHING I lower will have one of these installed from here on out. they make cruisin happy.
I am also of the opinion that these would be of great help in airbag cars where the shaft angle goes to shite at certian ride heights...

 

Yours sounds like one I saw at a car show once, I swear that thing was nothing more than 2 u joints with the smallest little shaft connecting those 2 u joints together that I have ever seen in my life. Hey, you know what? Maybe that could be a contest on here. "Shortest shaft contest - send in a picture of your short shaft" Gary 4T950 Chevy Guy

 

What is the actual application of the Caddy double cardan joint? We've been using Jeep Cherokee front joints, but did hear that the Caddy one is easier to adapt to some yokes.

 

I know they had 'em in 64 and 67. both were sedan De Villes (big ass more door cars)both also had th400's and 472's
the Bronco version is for sure avalible on the 1991 nite package XLT.(kinda like a lightning bronco) 5.8 litre,E4od,shift on the fly.

I think even some of the later caddies had 'em too, but don't Quote me on that.

I apologize for officially hijacking this post.I am an asshole

 

Yep dragsters run couplers instead of driveshafts with uni's. Uni's would break in less than nano seconds with 7000Hp throug them no matter what size they were. couplers are a male/female splined joint system, they rely on the pinoin and the output from the clutch/transmission being near inline and no rear suspension travel at all.

Driveshaft length has to factor in 1 suspension travel 2 universal joint angles and 3 sliding of yoke in transmission. All stated in above posts. drive shaft failure is a very dangerous thing, I have not experienced it and never want to. So do your engineering math and make it safe and strong-and use a saftey loop it may just save your life one day!

 

"What is the actual application of the Caddy double cardan joint?"

I know that they used them in all the 429 powered cads ('64-67) because I've had to replace a few of them on the two '65s that I've owned. They are a cool design, and they do work well, but they're heavy, hard to rebuild, and there's not any aftermarket replacement (I worked at a parts store for a few years and tried to find 'em). I had them rebuild by a place called "Driveline service of San Jose" and I believe they get a kit with the actual joints to press in to the b ig cast carrier, and a ball that is installed after turning down the original ball that fits in a socket in the middle to act as the "C.V. joint".
Just make sure that you have someone pay close attention, I had one go bad shortly after rebuild, lucky for me they stood behind their work and redid it (I missed paso though ) If memory serves me correctly their about 6" center to center (+/-)

 

It depends on total suspension deflection, if you are running a hardtail (BTDT, dirt track tires, flat fix & 6 lbs air) you can actually run without a driveshaft using a u-joint for mating couplers, but if using rear suspension do not allow joints to bind, if you hit a big bump/hole it could f-up your afternoon.

 

Yep....really gotta watch the big dips in the road (usually on cell phones) and limit the # of jumps on any given night. I'd like to eventually put the axle behind the spring to lengthen the wheelbase and shaft.....maybe next winter. I already have a boatload of stuff this winter.

 

I've seen 'em run with just a coupler but i don't think I'd do that on one I drove.

I highschool we set up helms' '23 Bucket with a pair of CV joints from a Lincoln dirveshaft, I think they used 'em around 64 or 66. it was 2 CV joints and about an inch of drive shaft. Worked out to about 7" in all I think.
Worked like a champ.

 

I've always referred to this type as a 'duplex' u-joint, & the guy @ my driveshaft shop always knew what i meant.
They are available in many of the standard automotive sizes; try to look @ an eaton or dana catalog.
This double joint is the least i'd use if i were direct coupling w/ a hardtail rear.

 

Shortest you can go is twice the suspention travel distance yoke centre to centre,
this allows 15 degrees as the maximum angle for the UJ's.

It's better to go IRS and then you don't need a prop, just a coupler.

 

Wow, I wonder if Inkorekt is still waiting for an answer...

 

The car is done and Studebaker powered. It was at the Pileup. Please, for the love of Christ, stop digging up 3 y.o. threads that aren't that good.