i'm a little curious about this mod ,how many have done it and are you pleased with the mod ,  i'm a little confused have you put much research into how u-joints work together in rotation ?  from what i read the angle of the u-joints in a perfect world should be equal to each other , unless you are using a cv-joint .if you rotate your drive shaft up to relieve the driveline angle at the diff to straight (no angle) and no cv-joint up at the t-case your gonna have a ton of vibration ,killing your u-joints ,transfercase ,pinon bearings also seals .any one doing this mod can you cough up some more info ,and details , because i'm sure your just opening up another can of worms ,  i ,also would like better driveshaft angles . but need more info .

       JAKE THE SNAKE

It is reccomended to have even angles so someone does not have an extreme angle on one end and not much on the other. The rotation allows almost a streight line out of the diff. while decreasing the angle out of the t-case. I just rotated mine while I was upgrading my rear axle but have not had it on the road yet. I'll update you on it when I finish the rest of my mods.
Zig

It is reccomended to have even angles so someone does not have an extreme angle on one end and not much on the other. The rotation allows almost a streight line out of the diff. while decreasing the angle out of the t-case. I just rotated mine while I was upgrading my rear axle but have not had it on the road yet. I'll update you on it when I finish the rest of my mods.
Zig

I´m just a noobie here, but this answer is WRONG!!!  Equal u-joint angles are needed to cancel out the angular velocity variations inherent to any u-joint.

Taken from

http://www.lehmantrikes.com/trikes-design.asp?ID=16

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Driveshaft


Lehman Trikes, Inc. Drive System

There are three main components to a basic drive shaft system:

1. Front universal joint
2. Drive shaft, and
3. Rear universal joint
The purpose of the shaft is to transfer power from the motorcycle transmission to the differential. The universal joints are required because the differential is offset and at an angle to the transmission.

Driveshaft Angle

All universal joints are designed to have a minimum of 1/2 degree of working angle. This angle is necessary in order to keep the needle bearings contained in the caps rolling. At angles less than 1/2 degree, the needles stay locked in the same position and wear into the cap, causing vibration and eventually failure.

Vibration

All universal joints vibrate. This is a property due to the design of the joint.

So the next question is: "If universal joints vibrate, then why does my car not vibrate?"

When a drive shaft is designed for application in a car, the joints are always in pairs. When there are two joints, they can be phased so they cancel each other out and no vibration is felt.

The universal joints work as follows:

When the output shaft turns, the two caps of the front universal joint must turn around the center of the output shaft.

When we look at the opposite side of the universal joint the other two caps on the universal joint must turn about the center of the drive shaft.

Because the drive shaft is at some angle to the output shaft, the cross of the universal joint must wobble back and forth to allow the bearing caps to trace these circles out while rotating.

This causes the rotating speed of the drive shaft to fluctuate on every turn, at first speeding up slightly faster than the output shaft, then slowing to slightly below the output shaft speed. If this effect is not counteracted with a second universal joint, it will create vibrations.

At the other end of the driveshaft, there is a second universal joint. This joint is timed to the front universal joint in order to be exactly opposite to it. When the drive shaft speeds up from the action of the front universal joint, the action of the rear universal joint slows it down, and vice versa. This produces a constant shaft speed at the differential shaft.

Automotive drive shafts are not straight for the reasons explained above. The rear end moves up and down, so the drive shaft can never be perfectly straight.


================

HTH,

justanoob

Good call newie I did not calirify enough The dirveshaft is not a streight line, it's almost streight, and at ride height it should have close to even angles. I only used the guess technique when setting the drive shaft angle without the rotation and it held up fine (with no vibration). So I used it again.
As the drastic angle is concerned, I only know what I've seen, and I have yet to see a Heep with even driveshaft angles, and the ones in my club that run 37's or smaller, drive interstate speeds with out much vibration. I had over 20,000 on my 3" lift with little vibratoin. I'll let you know how it rides when I get it out of the shop.
I'm sure that Mr. (Tracker Guru) Hagen will streighten me up when he gets back on line.
Zig

Ive rotated mine and I dont have any more vibration than before, that I can tell.  

Later,
Bill

The two joints are to be the same angle when the rig is in driving position. Mine does come out straight but I have dropped the center crossmember to achive almost no angle at the Tcase.  Anyone who says this wont work hasnt tried it. Ive been running this way for close to 200,000 miles now. Dont think for a second I would live with a vibration. Ive had no problems with pinion seals, ujoints or bearings. If there is a down side I havent found it. Almost everyone in our club has done this and Ive heard no complaints of a vibration or any other problems.

Mike

BTW Zig. If your two angles do not match you should try to drop your Tcase bracket too. On the passenger side remove the two 14mm bolts and space it down as needed then put in some longer bolts. Theres easily room to drop it 1 inch without having the t case hang below the frame or pull the shifter through the floor.

Mike

great replys   .cool guys !!  

Mikerpm4x4   you dropped the t-case . how did that affect your front shaft , i will be looking at the t-case tomorrow  , did you cut and weld the spring seats or just rotate it with the upper heim joint  bracket ??

 t-case drop .  can i get more info on the t-case lowering  i,looked at the passenger side looks straight forward ,what about drivers side . do i have a different mount ,i have a 97 4dr.   if i lower the one side it looks like it will twist all the rubber mounts  , i don't think you can just lower one side .because of the motor mounts .any info would be great would really like better angles


                      Jake
                                                   

I have been running the rotated rear axle for 10,000 miles
now, no problems, I think I like the T-case up highter, I
have some scrapes on it where it's at, I don't want it lower,
at least until Mike does an article on the belly pan he built.

I have thought about it for a while, but I was just going to
just put a peice of steel sheet acros the bottom of the frame,
I like Mike's full pan that has some rocker protection too,
How bout it mike give us the goods on ur Belly Pan !!
What thickness steel and such.

Thanks,
Darrin

Mike,
I'll check the t-case this weekend when I finish up the Anvil/power steering etc. I hope to have it on the road by sunday, but still have a long way to go.
Could you send me a pic of your front crossmember if you have one? I have to do a bit of BFH/torch modifying to it and wanted to see if my thoughts were anything like what you did.
Zig