driveshaft slope question

so I am reading a tech article on pirate4x4. I have a comanche with about 7” lift and a for 8.8 in the rear. it has the factory slip yoke, but I think I need to do a slip yoke eliminator down the road and get a CV joint.

anyways I just picked up a dana 44 and I need to weld new perches on top of it, there is just a little vibration with the current setup, but I would like it to be no vibration.


I believe I have figured out that I have “up” slope but would hope that some people with more experince can double check me.

T-case points down 4*
driveshaft 13*
rear pinion points up 12*


if I understand right, these slopes are opposite so I need to add the lesser # to the greater # to get my operating angles, which would be:


T-case 4+13= 17* operating angle

rear pinion 12+13= 25* operating angle

http://www.pirate4x4.com/tech/billavista/PR-shaft/index2.html

I may have this bass ackwards but I think it's the other way around.
Minus instead of plus so to speak.

T case down 4
DS 13
rear pinon 12

So a difference/operating angle (actual angle of U joint) of 9 degrees Tcase to DS
and 1 degree DS to pinion difference/operating angle, making a variance between either end of 8 degrees.
IIRC without an SYE you want less than 2-3 degrees difference between either end's operating angles, so a TC drop and shims are in order or, ideally an SYE.
An SYE could care less what the TC to DS angle is at as long as the pinion to DS difference is near 0.

Someone PLEASE correct me if I am wrong. I have been know to have "formula dyslexia" from time to time.

i am thinking of a sye and cv driveshaft, just trying to get an understanding and the formulas correct before i weld on new perches to the dana44. i was out in town and stopped by 4wheel parts just browsing and picked up so 6* shims. im now

4* tcase
15* driveshaft
7* pinion

with your math that puts me at
11* operating angle at t-case
8* operating angle at the pinion to DS
took for a quick spin and took away alot of the vibes, but this setup is only temporary and was a experment to see what would happen.

i pulled this from the tech article:

[FONT=Arial, Helvetica, sans-serif][/FONT]
[FONT=Arial, Helvetica, sans-serif]If both slopes are in the same direction (up or down), subtract the lesser number from the greater to obtain the operating angle.[/FONT]
[FONT=Arial, Helvetica, sans-serif]If both slopes are in different directions (one up and one down), add the lesser number to the greater to obtain the operating angle.[/FONT]


wouldnt the t-case pointing down and the pinion pointing up mean the slopes are in different direction? forgive me if im mentally challanged.

Seems like your really over thinking this whole thing IMO. At 7" of lift a SYE is much needed. If your going to weld on new perches why not install a SYE and slide the 44 under your rig and rotate the pinion up till its 2* below ds angle and tack weld them. Pull the axle out and burn them in. No need for all this mathematical confusion. Sure it all sounds and looks good on paper and may work? just seems easier to get in there and get dirty figure it out. Just a thought...

When you cut the old peches off take note of how far they are off the end of the axle so it stays centered under the jeep.

Something else to read if you haven't http://www.4xshaft.com/driveline101.html


Welding tips: You can go overboard, but it's also you're safety. The first tip is that if you're not sure you can do it, don't try it on something that your life depends on. Practice on stuff you can screw up and redo if you have to....

Oh and another thing to add.... Make sure the weight of the jeep is sitting on the axle, snug the leafs to perches. Rotate pinion angle to set angle.

:cheers:

thanks for the link. i had quite a bit of freetime today and was trying to figure out setting up for a cardan style driveshaft, and a cv driveshaft. never hurts to learn or try learning something new. and i think im going to do it right and go for a sye and cv driveshaft. the new axles have lower gears and lockers so i was in a hurry to slap them in but the setup i have now is fine so ill take my time and get the right parts.

Yeah man no worries.

http://www.stu-offroad.com/axle/pinion/pinion-1.htm
http://www.4x4wire.com/tech/pinionangle/

Oh and you maybe needing this too...
http://mikestrawbridge.com/blog/2010/04/installing-a-slip-yoke-eliminator-sye-in-a-np231/

Good luck with the build
:cheers: