Driveshaft with 2 cv joints???

[hunter29078]

I know they make them for the front but why not for the rear? Probably a stupid question but would it not help to have 2 cv's on the rear?

 

[Hogback Fabrication]

Why do you think you want CV's on both ends of a driveshaft?

 

[hunter29078]

Not exactly sure other than it helps with the angles. Without any cv joints perches must be moved, or wedges must be placed to set the pinion angle. No problem there, I have never had a rear shaft with a cv joint, but I have read that pinion angle does not have to be set with a cv joint. The same places that sale a driveshafts with cv joints sale fronts with 2 and claim they are better and easier on the driveline. So why is it not true with the rear. With the wheelbase of the k5, the angle of the driveline gets worse with lift and, worse with a doubler. So just wanted to know, before I decide on my driveshaft.

 

[blazinzuk]

Only time I have ever seen it was on show trucks that actually had a front driveline.

And on some zuks that are using centered rear axles with the stock sami case. But you are dealing with 2 different angles. On a truck with less than oh say 20" of lift not really needed

 

[4X4HIGH]

MANY Cadillac's used a driveshaft with a CV at both ends. There is really no reason other than cost that you couldn't do one for your rig but you really only need a CV at one end to make things happy.

 

[Hogback Fabrication]

Not exactly sure other than it helps with the angles. Without any cv joints perches must be moved, or wedges must be placed to set the pinion angle. No problem there, I have never had a rear shaft with a cv joint, but I have read that pinion angle does not have to be set with a cv joint. The same places that sale a driveshafts with cv joints sale fronts with 2 and claim they are better and easier on the driveline. So why is it not true with the rear. With the wheelbase of the k5, the angle of the driveline gets worse with lift and, worse with a doubler. So just wanted to know, before I decide on my driveshaft.

What places are these? CV joints on both ends of a shaft are VERY far and in between, the

Without a CV driveshaft there is a good chance you won't have to mess with shims (depends on a lot of things of course). With a CV driveshaft, it's guaranteed you'll need to mess with the pinion angle. I think you have that part backwards.

With a lifted Blazer (at 4" or more anyway), a CV rear driveshaft is the only guaranteed way to get rid of all driveline vibrations (though many have no issues that they can feel).

How much lift are you planning on?

 

[hunter29078]

What places are these? CV joints on both ends of a shaft are VERY far and in between, the

Without a CV driveshaft there is a good chance you won't have to mess with shims (depends on a lot of things of course). With a CV driveshaft, it's guaranteed you'll need to mess with the pinion angle. I think you have that part backwards.

With a lifted Blazer (at 4" or more anyway), a CV rear driveshaft is the only guaranteed way to get rid of all driveline vibrations (though many have no issues that they can feel).

How much lift are you planning on?

I am planning on 6" of lift. And yes I am a little confused. I have mainly delt with stock type vehicles, and I am just now getting into modifying my truck. I am going to add the 14bolt to the rear and put in a different x-case. Since I will have to have another DS, I am trying to learn as much as I can before I decide on what to do.

So with a regular D.S. the yoke on the back of the case needs to run parrallel with the yoke coming from the axle?

And I am assuming that with a lift that the angle is to great for the u-joint and that is why they have the t-case lowering kit which drops the angle of the case's output shaft to be pointed more towards the axle?

And the cv joint allows the t-case to stay in its same position and by shiming or rotating the perches, then the axle will be pointed toward the t-case (2 degrees below being exact)?

And this is easier because you are only having to move 1 thing instead of 2? And you can retain the stock transfer case mounting position.

So maybe the better question would be that if you have 2 cv joints on the rear D.S. would it be possible the retain the stock axle angle and the stock t-case angle?

 

[72blazerguy]

So with a regular D.S. the yoke on the back of the case needs to run parrallel with the yoke coming from the axle?

So maybe the better question would be that if you have 2 cv joints on the rear D.S. would it be possible the retain the stock axle angle and the stock t-case angle?

Yes, with a regular driveline, you need to have the TC and pinion angle close to the same. Like stock .......

http://www.4xshaft.com/

http://www.highangledriveline.com/tech_corner_for_drivelines.html

It seems you may be missing the point. If the TC and pinion angle are the same, no cv required. The slope of the driveline is not the important piece. You need to worry about the difference between the TC and pinion angle.

 

[Blue85]

This was just discussed a couple of weeks ago. Somebody had one from a Cadillac and planned to put it on the truck. The biggest advantage is that there will be no vibe as the suspension cycles through it's range. But usually if you have a lot of flex or bounce going on, a little driveline vibe isn't noticeable.

Most CVs have more limited range of motion than a standard U-joint. If you want more flex, that's an even more expensive joint, which you pay for twice. Much cheaper to just set the angles correctly.

 

[4X4HIGH]

Yes, with a regular driveline, you need to have the TC and pinion angle close to the same. Like stock .......

http://www.4xshaft.com/

http://www.highangledriveline.com/tech_corner_for_drivelines.html

It seems you may be missing the point. If the TC and pinion angle are the same, no cv required. The slope of the driveline is not the important piece. You need to worry about the difference between the TC and pinion angle.

Actually, you do need to worry about the "slope" of the driveline even if the t-case and pinion angles are the same. The reason is that a U-joint will prematurely fail if the working angle is more than 3 degrees. With a short wheel based vehicle it is impossible to achieve the same angle at the t-case and the pinion while maintaining no more than a 3 degree working angle on the U-joints. This is why people use a CV shaft when they lift a short wheel based vehicle. Usually with a lift up to 4" you can get away without using a CV shaft but anything more and you are either going to have vibes OR you will continually eat U-joints without a CV shaft.