cv,u,double cardan joints???

[Kilo19]

so this may be over kill here but here it goes.

i'm looking at a sm465/np205 set up, i've seen a lot of info about a doubler, but don't think it'll fit in a CJ5 , can anyone confirm? if it doesn't, no big deal, the crawl ratio would be cool to have, back to the question, with the 465/205 set up am i going to be too close to my rear axle (gm 12bolt) to use a u joint? or is it going to have to be a cv joint, or double cardan.

i don't know much about this area, (yet) any help as to the difference in them, and when one would be needed, best one to use and one to stay away from.

thanks in advance you guys

 

[BusaDave9]

The doubler won't fit. The CJ5 has a very short steep driveshaft even from the factory.
Since you will be getting a new driveshaft anyway I recommend getting a double-cardan joint. With that big rear end of yours (I'm talking about the GM 12 bolt) that will make the driveshaft reach even a bit further downward to reach the yoke. Do you have a lift? that will increase the angle even more.
I have a lifted CJ5 with a AMC20 . I started off with a standard U joint drive shaft but ended up getting a Tom Wood's double-cardan joint.

 

[Kilo19]

big rear end, ha, have you seen me, wait i guess you haven't

i've heard alot of good things about the tom jones drive shafts and was gonna look at getting them

lift- yes and no

i have a soa, with axles already set up for that, i think the pit arm and everything is built for it. i'll have to take a pic and show you guys, and stock yj springs.

 

[Old Dog]

That drive train is gona be a tight fit. A double cardan shaft will be needed I'm sure. There's a lot of info on Tom Woods site on how to measure for a new shaft, and how to set the pinion angle.
Are you going to run full width axles or cut them down some?

 

[BusaDave9]

i have a soa, with axles already set up for that, i think the pit arm and everything is built for it. i'll have to take a pic and show you guys, and stock yj springs.

SOA in a CJ5 . Yes you will need a double-cardan joint. Stock YJ springs don't have much arch but it will still be a steep angle. Also you want to make sure the yoke points up toward the TCase yoke in such a way that there isn't much angle on the u joint at the diff. The double-cardan joint should have all the angle.

 

[csuengr]

That would be Tom Woods, not Tom Jones.

That SM465 NP205 combo in long. GM just had to put in that 7" spacer. With a spring over you may not be able to make a regular CV work. It's going to awfully short and awfully steep angle.

 

[BusaDave9]

For a quick, useless note on terminology. The terms CV joint and double-candan joints are often used interchangeably.
But to be exact a CV joint is like this:

CV-Joints
And a Double-Cardan Joint is 2 U- joints together like this:

Double-Cardan Joint

A double-candan joint is a type of CV joint.
So every double-candan joint is a CV joint not all CV joints are double-candan joints. Is that clear as mud?​

 

[Kilo19]

That drive train is gona be a tight fit. A double cardan shaft will be needed I'm sure. There's a lot of info on Tom Woods site on how to measure for a new shaft, and how to set the pinion angle.
Are you going to run full width axles or cut them down some?

No I wasn't planning on cutting them.

I saw I put jones instead of woods. Sorry there mr woods. Mind was else where.

This is great guys keep it coming, I have a thought on helping the rear shaft length and angle. Let me draw it to explain better.

Thx to all

 

[csuengr]

Listening to some vinyl were ya?

My my my...Delilah

 

[Kilo19]

alright guys i've been doing some reading (uh oh) and looking at the tom "woods" website i saw where he, and you busa, mentioned rotating the axle up toward the TC, ok i see the reason for this, but he's my question i can't wrap my mind around yet.

how am i going to know what angle to rotate the axle?

speaking hypothetical, i could put the springs on the frame and attach the axles, but i would be guessing at what angle to put it at, and the only way to find out how much angle would be to put the drive train in, so does that mean i have to attach the axles and drive train, figure out my angle then take off the rear axle, remove springs/perches and reweld reattach?

let me know if this make sense.

 

[BusaDave9]

how am i going to know what angle to rotate the axle?

In theory the yoke on the differential should point at the yoke on the TCase. This way the U-joint at the diff will have 0° angle. It should not be angled at all.
Let me explain why. When a U joint is at any angle at all it forces the drive-shaft to speed up and slow down with each rotation.

In the above picture the angle of the front u-joint is the same as the rear u-joint. This is how the jeep and all vehicles with U joints come from the factory. This way as the front u joint tries to speed up and slow down the driveshaft then the rear u joint cancels that rotational vibration since it is at the same angle. These 2 angles must be the same.
A double-cardan joint has 2 u-joints together and these 2 u-joints cancel out eachother's rotational vibration. Therefor the ujoint at the differential should not have any angle or it will cause a rotational vibration.

That's the theory and that's how most builders set up a double cardan joint. In reality Tom Wood and other experts say if there is zero angle at the rear u-joint it wears oddly and the axle pinion should be tilted down about 1°


To try to explain why a u joint speeds up and slows down with each rotation imagine a u joint bent at an extreme angle.

How fast is the outer edge of the u -joint turning? It depends on how far it is from the center. Just like a the outer edge of a big tire is moving faster than the edge of the wheel it is mounted on.
The problem is as the u joint rotates the outer edge is sometimes closer to the center of the yoke.
This may be hard to visualize. I might be able to illustrate it better when I get home and can use Photoshop.

 

[Kilo19]

excuse me for asking but, wouldn't installing a double, double cardan joint solve all this, one on each said of the shaft, or are they not designed to work like that, the angle/degree issue. (no offense on what you just said, Busa, that has helped alot) just throwing another idea out there.

also, what about this.

im gonna be putting in a new type, tubluar home made bumper, i know what your thinking, great home made right, but what if i made it in a way that the axles, and springs all moved back a few inches? how much would be too much, how much would be enough, or is this too much to do, am i way over my head on this one.

i know if heard of people (my cousin's husband, the guy who gave me the jeep, wanted to put in a 350 with a 700r4, and was gonna extend the axle back 11 inches, i said no way im ok with a stick shift.

thanks again for the help, its really great asking you guys

 

[BusaDave9]

wouldn't installing a double, double cardan joint solve all this, one on each said of the shaft, or are they not designed to work like that, the angle/degree issue.

Yes, in theory, that should work. You wouldn't need to worry about the angle at either yoke. But it's unnecessary. Each u-joint is another wear point and potential failure area. Plus a double-cardan joint can have some flex. Look at this pic.

It's good to have one end mounted with a u joint.

 

[Kilo19]

so would this be a safe bet on what mine would "could" look like?

 

[BusaDave9]

Yes, that's what you need

 

[Kilo19]

Thx that helps. I know this is a side question but with the shackles and springs the axle will travel front/back a little. Do I need to find a specific driveshaft to accommodate this or is that understood for drive shaft shops?

 

[BusaDave9]

A standard slip joint on a drive shaft should account for normal axle movement.
In front if a shackle reversal was installed it is often necessary to get a driveshaft with extended travel in the slip joint. That's what I got for my front.

 

[Kilo19]

Ok for me no shackle reversal. Gonna "try" to keep it simple. Normal slip joint. Gotcha