PDA

View Full Version : School me on pinion angles


MDH33
11-03-2006, 11:19 AM
Making some modifications to my suspension and I think the pinion and driveshaft angles may be affected. What should I be measuring and how to correct?

:confused:

wesintl
11-03-2006, 12:18 PM
Optimal for a cardan ds you need the angles to be the same at each (3rd, case) end. The issue will be driveline vibration. On a truck with more lift like 4+ or SO you could max out the operating angle of the u joints. This is why folks cut and turn the front. The rear is no big deal to point the pinion up but then you must use a Double cardan joint at the tcase end because the ujoint angles are no longer the same. Longer than stock shackels also play into this and shims help correct pinion angles in the front. Although as tires get bigger having a relaxed pinion angle can help steering.

See DS 101
http://www.4xshaft.com/driveline101.html

Uncle Ben
11-03-2006, 02:11 PM
Optimal for a cardan ds you need the angles to be the same at each (3rd, case) end. <snip>http://www.4xshaft.com/driveline101.html


Oops...you bad....

Double Cardans are used when the flanges at the T-case and pinion CAN NOT be equal. If the angles are the same then u-joints at both ends are the requirement. When you have to rotate the pinion up and point it at the T-case while the T-case obviously is still on a horizontal plane then you use a DC at the T-case end. Harmonic vibrations are caused when angles do not cancel each other out. DC work by both joints in the DC operating at exactly the same angle thus canceling each other out, while the lower joint (pinion) is not at an angle so it doesn't need harmonic canceling. Clear as mud? :rolleyes: :blah: :cheers:

wesintl
11-03-2006, 02:26 PM
Oops...you bad....

Single cardan is a u joint, no?

MDH33
11-04-2006, 09:45 AM
Thanks for the replies. The link had lots of great info.

The direction of the shims still has me puzzled a bit. Also, if using a double cardan driveshaft in the rear, isn't there a risk of the front of the pinion not getting any oil because it is pointed up? How could you fill the diff properly if it's not level??

Right now, my rear has some small shims and it's almost level. The front, however is now pointing up slightly towards the TC after adding longer shackles.

Uncle Ben
11-04-2006, 10:25 AM
Single cardan is a u joint, no?

Interesting....never thought about that but you are correct. U-Joint = Cardan......2 U-joints in one yoke = Double Cardan. "Hey momma.....I got edgekated today!" :woot: :woot: :perry:

Uncle Ben
11-04-2006, 10:29 AM
Thanks for the replies. The link had lots of great info.

The direction of the shims still has me puzzled a bit. Also, if using a double darcadn driveshaft in the rear, isn't there a risk of the front of the pinion not getting any oil because it is pointed up? How could you fill the diff properly if it's not level??

Right now, my rear has some small shims and it's almost level. The front, however is now pointing up slightly towards the TC after adding longer shackles.


The pinion will still get oil as the ring gear throws oil into a large port that floods the pinion bearings. You are correct about the check hole, however. It will need to be raised accordingly. A big down side of running DC's on a trail rig is the slip yoke gets moved to the pinion end of the shaft which means it gets beat up and dirty.

Romer
11-04-2006, 10:49 AM
Interesting....never thought about that but you are correct. U-Joint = Cardan......2 U-joints in one yoke = Double Cardan. "Hey momma.....I got edgekated today!" :woot: :woot: :perry:

Guess you may not have to go to Iraq after all (pic from Mud on Kerry gaff)

gcmandrake
11-05-2006, 03:03 PM
Also check out Roger Brown's 4Crawler site:

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml

the Other Matt

Red_Chili
11-07-2006, 10:04 AM
One thing to keep in mind (which Roger mentions) is allowing for axle wrap in the rear. That is, if you make the front and rear ends of the DS match angles, then apply power, you are now 2* off or so.

So figure the rear pinion to be about 2* down from matching, and you are stylin'.

MDH33
11-08-2006, 07:16 PM
Thanks for the replies, all. :thumb:

I did some measurements after my shackle replacement. Maybe some of you Mathematicians can give me an interpretation of what I need to do as far as axle shims. Here are my measurements:

http://mdhuber.smugmug.com/photos/109028432-M.jpg

leiniesred
11-09-2006, 02:17 PM
Wow, great images!

For vibe-free with a single cardan shaft:

Well, I'd tip the rear down with a 3 degree shim.

The front, I'd be more concerned with caster angle to keep 'er tracking straight on the road. Death wobble sucks! I don't know what stock is, but I would aim for that and forget about trying to get the pinion angles right. I would guess you have longer than stock front shackles which have tipped the pinion up. I would guess The original angle was close to 90, so I would try for a 8 degree shim. (The front torques the pinion DOWN under load, but you don't really "cruise" in 4x4 do you?)



Get in here cruiser guys and tell us what the front original angle was!

wesintl
11-09-2006, 02:23 PM
Get in here cruiser guys and tell us what the front original angle was!

-1 iirc...

Those are some cool images.

MDH33
11-09-2006, 06:50 PM
Ok, it's starting to make sense. The force exerted on the diffs from the drive shafts will cause some spring wrap, so they should not be parallel at rest. Both pinion flanges should point down: -1˚ in front and about -2˚ in back?

The rear currently has a 2.5˚ shim, so if I replace that with a 6˚, the rear diff will go from +1.5˚ to -2˚. The front has no shim currently and it is tilted up +7.5˚, so an 8˚ shim would put it at -.5˚. This would be with the thick parts of the shims facing away from the TC, front and rear. Am I thinking correctly?

leiniesred
11-10-2006, 09:21 AM
exactly.

All of this will change when you get tired of the pinion flange walking you sideways off of rocks and you grow weary of denting your driveshafts on ledges.

Then, you'll get double cardan shafts and point the pinions right at the t-case. You'll cut the spring plates off the rear and rotate the axle, then you'll cut and rotate the front knuckles and go to a high pinion differential on the front...

-PEACE!

Uncle Ben
11-10-2006, 09:25 AM
exactly.

All of this will change when you get tired of the pinion flange walking you sideways off of rocks and you grow weary of denting your driveshafts on ledges.

Then, you'll get double cardan shafts and point the pinions right at the t-case. You'll cut the spring plates off the rear and rotate the axle, then you'll cut and rotate the front knuckles and go to a high pinion differential on the front...

-PEACE!

Exactly....oh wait....you just described an 80 series! :Princess: :lmao: :lmao:

MDH33
11-10-2006, 09:32 AM
exactly.

All of this will change when you get tired of the pinion flange walking you sideways off of rocks and you grow weary of denting your driveshafts on ledges.

Then, you'll get double cardan shafts and point the pinions right at the t-case. You'll cut the spring plates off the rear and rotate the axle, then you'll cut and rotate the front knuckles and go to a high pinion differential on the front...

-PEACE!

Thanks. hmmm, better options are out there it seems... If I had some welding skills I would probably lean towards the cut and turn. seems like a more solid, permanent fix.

I guess one concideration of mine is that with the shims, things can be easily changed in the event I decide to swap springs, or other parts.

Just thought of something else; the springs are new and I assume they will settle after some more use. this will change the angles again? or is it not enough to be concerned about? 8˚ in front seems like a huge shim, how important is it that I get that pinion flange pointing down -1˚? is close good enough? After a test drive yesterday, it doesn't drive terrible right now, just some wander.

I'm going to post my illustration with the measurements on MUD too and see what they think about those angles.

wesintl
11-10-2006, 10:00 AM
this will change the angles again? or is it not enough to be concerned about? 8˚ in front seems like a huge shim, how important is it that I get that pinion flange pointing down -1˚? is close good enough?

It would but probably not enough to be concerned with. Close is probably good enough. Like I said earlier as your tire grows steering is actually better in the + range. I think if your around 0 you'll be fine. For wander I would check and adjust the steering box, center arm and TRE. Also make sure the knuckles are tight, same with wheel bearings. :cheers:

I wouldn't be too concerned about cut and turn with ~2 lift. 4" + or SO, yes

Red_Chili
11-10-2006, 10:34 AM
Shims in the front are evil, IMHO. YMMV.
If you must, use weldable - and weld on. By all means RUN AWAY from aluminum or potmetal shims entirely!
Roger will make you custom shims out of steel that are very well made. Should your needs change, he will exchange them too.

MDH33
11-10-2006, 10:51 AM
Shims in the front are evil, IMHO. YMMV.
If you must, use weldable - and weld on. By all means RUN AWAY from aluminum or potmetal shims entirely!
Roger will make you custom shims out of steel that are very well made. Should your needs change, he will exchange them too.

Why are shims in the front worse?

I don't like the idea of the thick shim because it's going to lift the front even more... I'm going to contact Roger when I get back from vacation and see what he recommends.

Thanks for all the replies. :risingsun

MDH33
11-10-2006, 10:55 AM
It would but probably not enough to be concerned with. Close is probably good enough. Like I said earlier as your tire grows steering is actually better in the + range. I think if your around 0 you'll be fine. For wander I would check and adjust the steering box, center arm and TRE. Also make sure the knuckles are tight, same with wheel bearings. :cheers:

I wouldn't be too concerned about cut and turn with ~2 lift. 4" + or SO, yes

Yeah steering is the next project when funds allow. New tie rod ends and a longer pitman arm I think will help. Maybe power steering conversion at some point too.

I have 4" lift springs and longer shackles, so the cut and turn seems like it might be worthwhile.