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My U-joints on my new drive shaft are going to bind

GsxrMike said:
So I want to keep my u-joint angles the same if I run my driveshaft like in the pic? I could drill and tap the top of my axle housing so I could "overfill" the diff to help pinion bearing lubercation correct?
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You want your joints to operate at the same angle regardless of wether your pinion is up or down. The only time the pinion joint is not at the same angle as a tcase joint is when you use a CV shaft. That is because the 2 joints in the CV are operating at the same angle and canceling each other out.

No need to drill and tap the housing. The fill plug is on the side of the pinion snout, so if you raise the pinion you automatically raise the fill port and allow more oil capacity.

Dik
 
As I understand it, one disadvantage to setting it up like that is that as the axle cycles up or down, as one angle is getting less the other is increasing. That has the potential for introducing vibrations.
 
Ok so does anybody want to tell me this is a bad idea b4 I remove my rear axle, cut my beautifully weld perchs, grind for days, reinstall axle, set angles, and weld new perches on?
 
GsxrMike said:
Ok so does anybody want to tell me this is a bad idea b4 I remove my rear axle, cut my beautifully weld perchs, grind for days, reinstall axle, set angles, and weld new perches on?
Click to expand...

Use a degree shim and put it in backwards to move the pinion up rather than down. That is all I did.


Dik
 
GsxrMike said:
Ok so does anybody want to tell me this is a bad idea b4 I remove my rear axle, cut my beautifully weld perchs, grind for days, reinstall axle, set angles, and weld new perches on?
Click to expand...

Well, I don't think we know enough about your setup. Tell us some more and we'll be able to help.

But, the idea is that if the operating angles (the difference between the pinion/t-case angles in relation to the driveshaft angle) are the same, the vibrations will cancel each other out (u-joints inherently vibrate when used at any angle).

You can actually have your pinion pointed up (like your previous picture) and have no vibes (that's what my rear shaft looks like), so long as the angles match.

The thing is that matching angles don't always equal no vibes, sometimes the angles are simply too steep and necessitate a CV driveshaft (this applies to pretty much any K5 with 4" or more lift).

Some people just live with the vibration.
 
Yea, why not take a picture of the setup and see if that helps. I'd personally rather run a more standard setup just because it's been done before more often.
 
Well I don't have a pic on hand but I am running a 208 tcase with a slip yoke. I have a 14bff rear and my driveshaft is about 34" long cap to cap. With my driveshaft installed as it sits my ujoints are operating at about 20* each. I clearenced the yokes on the tcase end just a little bit and it helped alot but what I am thinking is that if I rotate my rear axle to point the pinion above the tcase with my driveshaft installed and measure the angles to get them with in 1* or 2* of each other and reweld my perches both angle will be significantly less and I won't have to worry about binding. I can live with vibration (I going to be running 38.5 boggers). I would like to get it set up where my ujoints won't wear out every month but I guess I will just have to wait and see. A local guy told me I want to run my pinion angle 3*-5* less than my tcase angle because when I accelerate the torque on my axle will cause it to rotate up. When I asked him about breaking both angles over the same direction he said "no way" but he is a race car builder. I just want the darn thing to be strong enough to last a while with minimal vibration. As far as installing a shim...I am going to need alot more rotation than a shim will offer me. I will try to post up a pic tonight. Thanks for all of the help guys.
 
You've probably already said, but how high of a lift are you running?

I've got about as long of a driveshaft and the same rear end and I run a CV shaft which allowed me to rotate the pinion up to about 0 degrees of angle and also reduced the angles of the CV at the other end. I think that would be a better way to go if the money doesn't stop you.

If you really want to do it the other way, make really sure you cycle the suspension through it's travel to make sure you don't bind it up. I'd be worried about binding the pinion joint at full compression or hard acceleration. Some people run it that way though so I have to believe it works ok if it's setup right.
 
I'm not sure how much lift I have. I've got stock height 52/64 with about 6" shackles. I think I am going to try this and if this doesn't work then I will have to go with a cv shaft. I think I am going to set up the pinion angle 2* less than the tcase angle so under acceleration I don't get any vibes. Guess I'll see what happens. Thanks again guys for all of the help.
 
concrete numbers

Ok I took some measurements tonight and drew up a little diagram. I didn't pay attention in high school and have forgot all of my basic geometry skills. My t'case points down 6* and my rear axle points up 2*. The output shaft center is 13" higher than my pinion ujoint center. How much do I need to rotate my rear axle in order to have both angle breaking over the same way and the same degrees (if thats what I want?)?

picture.php
 
For a standard driveshaft, you need to rotate the pinion up 4 degrees. But as you do that, the angle at the transfer case will also decrease so you may only need to rotate 3degrees to keep them equal.

Also, if you're running 38's, you may want to back off the pinion rotation a degree or two to account for axle wrap. That would mean reducing the rotation to only go up 1 degree.

If your measurements are accurate and the joints aren't binding at full compression or droop, I'd run it like you have it and see if it gives you problems since you are pretty close already.
 
I am wanting to run my pinion up past 0* and start to angle it the other way. My joints are sitting to close to 20* with no flex and that is the whole reason for this thread. I want both angles to "break over" the same way. Not one way and then the other. Like in the previous diagram I made about 10 or 12 posts ago.
 
Alright I installed the driveshaft and it sits at 21* which I belive would give me a 15* angle at the t'case and a 19* angle at the axle. Doesn't sound like those are good angles to me.
 
Here's a diagram I made to help illustrate.

The top diagram is the setup (to scale) of what you have. You're correct the angle is about 20 degrees at the pinion, but 16 at the transfer case.

The second diagram shows the angles if you rotate the pinion up 4degrees. The pinion angle goes down a lot and the transfer case side goes down very little, but both are around 16 degrees. The advantage of this setup is that as the suspension cycles up and down, both drivehaft angles stay very close to each other (that's good).

The third diagram is the pinion rotated up 16 degrees and is what I think your asking about. Technically this works, since the result is both angles are about 7 degrees with a neutral suspension stance. (which is good).

The problem with this setup is that as the suspension droops, the transfer case angle will go up a lot, but the pinion side will stay relatively stable (that's bad). When the suspension compresses, the opposite happens. The angles are only equal with a neutral suspension stance even though they are smaller. Now if you setup the pinion like that diagram so that the suspension droop or compression keeps both angles below the max operating angle and don't bind, the only drawback to that setup would be potential vibrations when the suspension is drooping or compressing. That may not be noticable if those happen when the truck is moving slowly.

The lowest diagram is a CV setup. You can see that the operating angle of the 2 transfer case joints are about 5 degrees and the joint at the pinion is effectively 0. This gives you the same advantages as your setup above with very low operating angles, but also keeps the angles lower and similar as the suspension cycles. The downside is the extra cost.

I hope that helps a little.

angles.jpg
 
Thats fancy...I like it. I gotta go watch a movie with my family but I will be back on here in a couple hours. I was wanting to go with the 16* style like you show. I will post back with a couple questions I have in a bit. THANKS!

Alright I'm back. I like very much what you have done here. As far as the angles changing when the suspension cycles...the axle is not going to move straight up and down because it is piviting on one end and not on the other. Do you know what I mean? The front is stationary and the rear is what is going up and down.

Second thought...If I run the axle like the 3rd pic (16*) then the angles will be much less and there for even though they are going to change I don't think they will ever be very far off unless I am at slow speed doing alot of flexing which I don't think vibrations would be that relevant in that situation. Plus since I would be running my joints at a much smaller angle then the joints should last much longer.

I think I might try to pick up a 4* shim tomorrow and see how that works out for me. If it is still going to bind I will try the 16* idea.

Where did you come up with those drawings? Did you use a program or your brain and a calculator?
 
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If I run the axle like the 3rd pic (16*) then the angles will be much less and there for even though they are going to change I don't think they will ever be very far off unless I am at slow speed doing alot of flexing which I don't think vibrations would be that relevant in that situation
Click to expand...

You might be right, but I'd verify that before you weld anything. You can see that with just 4 degrees of rotation (equivalent to about 2-3" of suspension travel in your case), the pinion joint angle changes 4 degrees while the transfer case side doesn't change much. If you add a couple of degrees for axle wrap with those big tires the joints could see upwards of 6 degrees difference between the joints. If you have flexy springs, the numbers could be higher. If you loaded up the truck with gear or were towing, I could see potential issues with it. There's probably too many factors to know for sure though.

Where did you come up with those drawings?
Click to expand...

A program I use a lot called Rhino3d. There's a free demo here: www.rhino3d.com
 
Do you know if I rotate my axle 4* how many inches my pinion will come up? I am going to post some pics in a minute of my tcase joint and how far the driveshaft hands at full bind after being clearenced.
 
Here is a picture of my driveshaft hanging with the tcase joint in a full bind after i clearenced it a bit. You can see how I won't have much down travel with the axle before I run into big problems.
picture.php


And here is a pic of the t'case u'joint with the driveshaft installed.
picture.php


I'm going to run down a get a pic of the whole driveshaft to give better perspective.
 
I can only guess on how far the pinion will go up with only 4 degrees, but it's not very much. With a 14bff, I'd guess less than 2". The height changes less as the pinion rotates up and approaches vertical.
 
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